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smb.conf Fileproc File SystemDHCP, BIND, Apache HTTP Server, Postfix, Sendmail and other enterprise-class servers and software
kdump
NetworkManager daemon, and how to interact with it using the corresponding applet for the notification area.
/etc/sysconfig/network-scripts/ directory. Read this chapter for information how to use these files to configure network interfaces.
sshd service, as well as a basic usage of the ssh, scp, sftp client utilities. Read this chapter if you need a remote access to a machine.
rsyslog daemon, and explains how to locate, view, and monitor log files. Read this chapter to learn how to work with log files.
cron, at, and batch utilities. Read this chapter to learn how to use these utilities to perform automated tasks.
rpm command instead of yum. Read this chapter if you cannot update a kernel package with the Yum package manager.
kdump service in Red Hat Enterprise Linux, and provides a brief overview of how to analyze the resulting core dump using the crash debugging utility. Read this chapter to learn how to enable kdump on your system.
rpm utility. Read this appendix if you need to use rpm instead of yum.
/etc/sysconfig/ directory. Read this appendix if you want to learn more about these files and directories, their function, and their contents.
proc file system (that is, the /proc/ directory). Read this appendix if you want to learn more about this file system.
Mono-spaced Bold
To see the contents of the filemy_next_bestselling_novelin your current working directory, enter thecat my_next_bestselling_novelcommand at the shell prompt and press Enter to execute the command.
Press Enter to execute the command.Press Ctrl+Alt+F2 to switch to the first virtual terminal. Press Ctrl+Alt+F1 to return to your X-Windows session.
mono-spaced bold. For example:
File-related classes includefilesystemfor file systems,filefor files, anddirfor directories. Each class has its own associated set of permissions.
Choose → → from the main menu bar to launch Mouse Preferences. In the Buttons tab, click the Left-handed mouse check box and click to switch the primary mouse button from the left to the right (making the mouse suitable for use in the left hand).To insert a special character into a gedit file, choose → → from the main menu bar. Next, choose → from the Character Map menu bar, type the name of the character in the Search field and click . The character you sought will be highlighted in the Character Table. Double-click this highlighted character to place it in the Text to copy field and then click the button. Now switch back to your document and choose → from the gedit menu bar.
Mono-spaced Bold ItalicProportional Bold Italic
To connect to a remote machine using ssh, typesshat a shell prompt. If the remote machine isusername@domain.nameexample.comand your username on that machine is john, typessh john@example.com.Themount -o remountcommand remounts the named file system. For example, to remount thefile-system/homefile system, the command ismount -o remount /home.To see the version of a currently installed package, use therpm -qcommand. It will return a result as follows:package.package-version-release
Publican is a DocBook publishing system.
mono-spaced roman and presented thus:
books Desktop documentation drafts mss photos stuff svn books_tests Desktop1 downloads images notes scripts svgs
mono-spaced roman but add syntax highlighting as follows:
package org.jboss.book.jca.ex1; import javax.naming.InitialContext; public class ExClient { public static void main(String args[]) throws Exception { InitialContext iniCtx = new InitialContext(); Object ref = iniCtx.lookup("EchoBean"); EchoHome home = (EchoHome) ref; Echo echo = home.create(); System.out.println("Created Echo"); System.out.println("Echo.echo('Hello') = " + echo.echo("Hello")); } }
doc-Deployment_Guide
6
system-config-date command at a shell prompt (e.g., xterm or GNOME Terminal). Unless you are already authenticated, you will be prompted to enter the superuser password.
~]$ su -
Password:date command allows the superuser to set the system date and time manually:
YYYY with a four-digit year, MM with a two-digit month, and DD with a two-digit day of the month:
~]# date +%D -s YYYY-MM-DD~]# date +%D -s 2010-06-02HH stands for an hour, MM is a minute, and SS is a second, all typed in a two-digit form:
~]# date +%T -s HH:MM:SS~]# date +%T -s HH:MM:SS -u~]# date +%T -s 23:26:00 -udate without any additional argument:
~]$ date
Wed Jun 2 11:58:48 CEST 2010~]# ntpdate -q server_address~]# ntpdate -q 0.rhel.pool.ntp.org~]# ntpdate server_address...~]# ntpdate 0.rhel.pool.ntp.org 1.rhel.pool.ntp.orgdate without any additional arguments as shown in Section 2.2.1, “Date and Time Setup”.
~]# chkconfig ntpdate on/var/log/boot.log system log, try to add the following line to /etc/sysconfig/network:
NETWORKWAIT=1
/etc/ntp.conf in a text editor such as vi or nano, or create a new one if it does not already exist:
~]# nano /etc/ntp.confserver 0.rhel.pool.ntp.org server 1.rhel.pool.ntp.org server 2.rhel.pool.ntp.org
iburst directive at the end of each server line:
server 0.rhel.pool.ntp.org iburst server 1.rhel.pool.ntp.org iburst server 2.rhel.pool.ntp.org iburst
restrict default kod nomodify notrap nopeer noquery restrict -6 default kod nomodify notrap nopeer noquery restrict 127.0.0.1 restrict -6 ::1
~]# service ntpd restartntpd daemon is started at boot time:
~]# chkconfig ntpd onroot, and access permissions can be changed by both the root user and file owner.
/etc/bashrc file. Traditionally on UNIX systems, the umask is set to 022, which allows only the user who created the file or directory to make modifications. Under this scheme, all other users, including members of the creator's group, are not allowed to make any modifications. However, under the UPG scheme, this “group protection” is not necessary since every user has their own private group.
/etc/passwd file to /etc/shadow, which is readable only by the root user.
/etc/login.defs file to enforce security policies.
/etc/shadow file, any commands which create or modify password aging information do not work. The following is a list of utilities and commands that do not work without first enabling shadow passwords:
chage utility.
gpasswd utility.
usermod command with the -e or -f option.
useradd command with the -e or -f option.
system-config-users at a shell prompt. Note that unless you have superuser privileges, the application will prompt you to authenticate as root.
/home/username/. You can choose not to create the home directory by clearing the Create home directory check box, or change this directory by editing the content of the Home Directory text box. Note that when the home directory is created, default configuration files are copied into it from the /etc/skel/ directory.
| Utilities | Description |
|---|---|
useradd, usermod, userdel
| Standard utilities for adding, modifying, and deleting user accounts. |
groupadd, groupmod, groupdel
| Standard utilities for adding, modifying, and deleting groups. |
gpasswd
|
Standard utility for administering the /etc/group configuration file.
|
pwck, grpck
| Utilities that can be used for verification of the password, group, and associated shadow files. |
pwconv, pwunconv
| Utilities that can be used for the conversion of passwords to shadow passwords, or back from shadow passwords to standard passwords. |
root:
useradd[options]username
options are command line options as described in Table 3.2, “useradd command line options”.
useradd command creates a locked user account. To unlock the account, run the following command as root to assign a password:
passwdusername
| Option | Description |
|---|---|
-c 'comment'
|
comment can be replaced with any string. This option is generally used to specify the full name of a user.
|
-d home_directory
|
Home directory to be used instead of default /home/.
|
-e date
| Date for the account to be disabled in the format YYYY-MM-DD. |
-f days
|
Number of days after the password expires until the account is disabled. If 0 is specified, the account is disabled immediately after the password expires. If -1 is specified, the account is not be disabled after the password expires.
|
-g group_name
| Group name or group number for the user's default group. The group must exist prior to being specified here. |
-G group_list
| List of additional (other than default) group names or group numbers, separated by commas, of which the user is a member. The groups must exist prior to being specified here. |
-m
| Create the home directory if it does not exist. |
-M
| Do not create the home directory. |
-N
| Do not create a user private group for the user. |
-p password
|
The password encrypted with crypt.
|
-r
| Create a system account with a UID less than 500 and without a home directory. |
-s
|
User's login shell, which defaults to /bin/bash.
|
-u uid
| User ID for the user, which must be unique and greater than 499. |
useradd juan is issued on a system that has shadow passwords enabled:
juan is created in /etc/passwd:
juan:x:501:501::/home/juan:/bin/bash
juan.
x for the password field indicating that the system is using shadow passwords.
juan is set to /home/juan/.
/bin/bash.
juan is created in /etc/shadow:
juan:!!:14798:0:99999:7:::
juan.
!!) appear in the password field of the /etc/shadow file, which locks the account.
-p flag, it is placed in the /etc/shadow file on the new line for the user.
juan is created in /etc/group:
juan:x:501:
/etc/group has the following characteristics:
juan.
x appears in the password field indicating that the system is using shadow group passwords.
juan in /etc/passwd.
juan is created in /etc/gshadow:
juan:!::
juan.
!) appears in the password field of the /etc/gshadow file, which locks the group.
juan is created in the /home/ directory:
~]# ls -l /home
total 4
drwx------. 4 juan juan 4096 Mar 3 18:23 juanjuan and group juan. It has read, write, and execute privileges only for the user juan. All other permissions are denied.
/etc/skel/ directory (which contain default user settings) are copied into the new /home/juan/ directory:
~]# ls -la /home/juan
total 28
drwx------. 4 juan juan 4096 Mar 3 18:23 .
drwxr-xr-x. 5 root root 4096 Mar 3 18:23 ..
-rw-r--r--. 1 juan juan 18 Jun 22 2010 .bash_logout
-rw-r--r--. 1 juan juan 176 Jun 22 2010 .bash_profile
-rw-r--r--. 1 juan juan 124 Jun 22 2010 .bashrc
drwxr-xr-x. 2 juan juan 4096 Jul 14 2010 .gnome2
drwxr-xr-x. 4 juan juan 4096 Nov 23 15:09 .mozillajuan exists on the system. To activate it, the administrator must next assign a password to the account using the passwd command and, optionally, set password aging guidelines.
root:
groupadd[options]group_name
options are command line options as described in Table 3.3, “groupadd command line options”.
| Option | Description |
|---|---|
-f, --force
|
When used with -g gid and gid already exists, groupadd will choose another unique gid for the group.
|
-g gid
| Group ID for the group, which must be unique and greater than 499. |
-K, --key key=value
|
Override /etc/login.defs defaults.
|
-o, --non-unique
| Allow to create groups with duplicate. |
-p, --password password
| Use this encrypted password for the new group. |
-r
| Create a system group with a GID less than 500. |
chage command.
chage command. For more information, see Section 3.1.2, “Shadow Passwords”.
root:
chage[options]username
options are command line options as described in Table 3.4, “chage command line options”. When the chage command is followed directly by a username (that is, when no command line options are specified), it displays the current password aging values and allows you to change them interactively.
| Option | Description |
|---|---|
-d days
| Specifies the number of days since January 1, 1970 the password was changed. |
-E date
| Specifies the date on which the account is locked, in the format YYYY-MM-DD. Instead of the date, the number of days since January 1, 1970 can also be used. |
-I days
|
Specifies the number of inactive days after the password expiration before locking the account. If the value is 0, the account is not locked after the password expires.
|
-l
| Lists current account aging settings. |
-m days
|
Specify the minimum number of days after which the user must change passwords. If the value is 0, the password does not expire.
|
-M days
|
Specify the maximum number of days for which the password is valid. When the number of days specified by this option plus the number of days specified with the -d option is less than the current day, the user must change passwords before using the account.
|
-W days
| Specifies the number of days before the password expiration date to warn the user. |
root:
passwdusername
passwd-dusername
root:
chage-d0username
root, an unattended login session may pose a significant security risk. To reduce this risk, you can configure the system to automatically log out idle users after a fixed period of time:
root:
yuminstallscreen
root, add the following line at the beginning of the /etc/profile file to make sure the processing of this file cannot be interrupted:
trap "" 1 2 3 15
/etc/profile file to start a screen session each time a user logs in to a virtual console or remotely:
SCREENEXEC="screen" if [ -w $(tty) ]; then trap "exec $SCREENEXEC" 1 2 3 15 echo -n 'Starting session in 10 seconds' sleep 10 exec $SCREENEXEC fi
sleep command.
/etc/screenrc configuration file to close the screen session after a given period of inactivity:
idle 120 quit autodetach off
idle directive.
idle 120 lockscreen autodetach off
/opt/myproject/ directory. Some people are trusted to modify the contents of this directory, but not everyone.
root, create the /opt/myproject/ directory by typing the following at a shell prompt:
mkdir /opt/myprojectmyproject group to the system:
groupadd myproject/opt/myproject/ directory with the myproject group:
chown root:myproject /opt/myprojectchmod 2775 /opt/myprojectmyproject group can create and edit files in the /opt/myproject/ directory without the administrator having to change file permissions every time users write new files. To verify that the permissions have been set correctly, run the following command:
~]# ls -l /opt
total 4
drwxrwsr-x. 3 root myproject 4096 Mar 3 18:31 myproject/etc/group file.
/etc/group file.
/etc/passwd and /etc/shadow files.
Table of Contents
yum to unit content delivery with subscription management. The Subscription Manager handles only the subscription-system associations. yum or other package management tools handle the actual content delivery. Chapter 5, Yum describes how to use yum.
yum plug-ins that come with the Subscription Manager tools.
root because of the nature of the changes to the system. However, Red Hat Subscription Manager connects to the subscription service as a user account for the Customer Service Portal.
firstboot process for configuring content and updates, but the system can be registered at any time through the Red Hat Subscription Manager GUI or CLI. New subscriptions, new products, and updates can be viewed and applied to a system through the Red Hat Subscription Manager tools.
yum service through the Red Hat Subscription Manager yum plug-in.
yum.
yum.
root.
[root@server1 ~]# subscription-manager-gui
subscription-manager tool. This tools has the following format:
[root@server1 ~]# subscription-manager command [options]subscription-manager help and manpage have more information.
| Command | Description |
|---|---|
| register | Registers or identifies a new system to the subscription service. |
| unregister | Unregisters a machine, which strips its subscriptions and removes the machine from the subscription service. |
| subscribe | Allocates a specific subscription to the machine. |
| redeem | Autosubscribes a machine to a pre-specified subscription that was purchased from a vendor, based on its hardware and BIOS information. |
| refresh |
Pulls the latest entitlement data from the server. Normally, the system polls the entitlement server at a set interval (4 hours by default) to check for any changes in the available subscriptions. The refresh command checks with the entitlement server right then, outside the normal interval.
|
| unsubscribe | Removes a specific subscription or all subscriptions from the machine. |
| list | Lists all of the subscriptions that are compatible with a machine, either subscriptions that are actually consumed by the machine or unused subscriptions that are available to the machine. |
| identity | Handles the identity certificate and registration ID for a system. This command can be used to return the current UUID or generate a new identity certificate. |
| facts | Lists the system information, like the release version, number of CPUs, and other architecture information. |
| clean |
Removes all of the subscription and identity data from the local system, without affecting the consumer information in the subscription service. Any of the subscriptions consumed by the system are still consumed and are not available for other systems to use. The clean command is useful in cases where the local entitlement information is corrupted or lost somehow, and the system will be reregistered using the register --consumerid=EXISTING_ID command.
|
| orgs, repos, environments | Lists all of the configured organizations, environments, and content repositories that are available to the given user account or system. These commands are used to view information in a multi-org infrastructure. They are not used to configure the local machine or multi-org infrastructure. |
libvirt-rhsm, checks VMWare, KVM, and Xen processes and then relays that information to Subscription Manager and any configured subscription service (Certificate-based Red Hat Network or a local Subscription Asset Manager). Each guest machine on a host is assigned a guest ID, and that guest ID is both associated with the host and used to generate the identity certificate for the guest when it is registered.
system type of consumer.
system, meaning that each individual server subscribes to its own entitlements for its own use. There is another type of consumer, though, which is available for server groups, the domain type. domain-based entitlements are not allocated to a single system; they are distributed across the group of servers to govern the behavior of that group of servers. (That server group is called a domain.)
system consumer and added to the inventory individually.
domain entitlements apply to the behavior of the entire server group, not to any one system.
domain entitlements using the Red Hat Subscription Manager tools, and the entitlement certificate is replicated between the domain servers.
subscription-manager-gui
rhsm.conf configuration file points to the local subscription service (in the hostname parameter) and the local content server (in the baseurl parameter). The Subscription Manager configuration is described in Section 4.13, “Configuring the Subscription Service”.
subscription-manager-gui
.zip file. Save the file to some kind of portable media, like a flash drive.
certificates.zip file. Unzip the directories until the PEM files for the entitlement certificates are available.
import command. For example:
# subscription-manager import --certificate=/tmp/export/entitlement_certificates/596576341785244687.pem --certificate=/tmp/export/entitlement_certificates/3195996649750311162.pem Successfully imported certificate 596576341785244687.pem Successfully imported certificate 3195996649750311162.pem
cert.pem file directly into the /etc/pki/consumer directory. For example:
cp /tmp/downloads/cert.pem /etc/pki/consumer
register command with the user account information required to authenticate to the Certificate-Based Red Hat Network (the credentials used to access subscription service or the Customer Portal). When the system is successfully authenticated, it echoes back the newly-assigned consumer ID and the user account name which registered it.
register options are listed in Table 4.2, “register Options”.
[root@server1 ~]# subscription-manager register --username admin-example --password secret
7d133d55-876f-4f47-83eb-0ee931cb0a97 admin-example (the new consumer UUID and the account used for registration)--org option in addition to the username and password. The given user must also have the access permissions to add systems to that organization.
[root@server1 ~]# subscription-manager register --username admin-example --password secret--org="IT Department"7d133d55-876f-4f47-83eb-0ee931cb0a97 admin-example(the new consumer UUID and the account used for registration)
[root@server1 ~]# subscription-manager register --username admin-example --password secret --org="IT Department" --environment=Dev1,ITallregister command returns a Remote Server error.
register command has an option, --autosubscribe, which allows the system to be registered to the subscription service and immediately subscribed to the subscription which best matches its architecture in a single step.
[root@server1 ~]# subscription-manager register --username admin-example --password secret --autosubscribe--activationkey option.
--org option, but in multi-org environments, the --org option is required. The organization is not defined as part of the activation key.
# subscription-manager register --activationkey=1234abcd --org="IT Dept"| Options | Description | Required |
|---|---|---|
| --username=name | Gives the content server user account name. | Required |
| --password=password | Gives the password for the user account. | Required |
| --org=name | Gives the organization to which to join the system. | Required, except for hosted environments |
| --environment=name | Registers the consumer to an environment within an organization. | Optional |
| --name=machine_name | Sets the name of the consumer (machine) to register. This defaults to be the same as the hostname. | Optional |
| --autosubscribe | Automatically subscribes this system to the best-matched compatible subscription. This is good for automated setup operations, since the system can be configured in a single step. | Optional |
| --activation_key | Applies existing subscriptions as part of the registration process. The subscriptions are pre-assigned by a vendor or by a systems administrator using Subscription Asset Manager. | Optional |
| --force | Registers the system even if it is already registered. Normally, any register operations will fail if the machine is already registered. | Optional |
unregister command. This removes the system's entry from the subscription service, unsubscribes it from any subscriptions, and, locally, deletes its identity and entitlement certificates.
unregister.
[root@server1 ~]# subscription-manager unregister
register command. This command passes the original UUID for a system to issue a request to the subscription service to receive a new certificate using the same UUID. This essentially renews its previous registration.
register command uses the original ID to identify itself to the subscription service and restore its previous subscriptions.
[root@server1 ~]# subscription-manager register --username admin-example --password secret --consumerid=7d133d55-876f-4f47-83eb-0ee931cb0a97
| Options | Description | Required |
|---|---|---|
| --consumerid | Gives the consumer UUID used by an existing consumer. The system's consumer entry must exist in the Red Hat subscription service for the reregister operation to succeed. | Required |
| --username=name | Gives the content server user account name. | Optional |
| --password=password | Gives the password for the user account. | Optional |
subscription-manager-gui
subscription-manager-gui
--pool option.
[root@server1 ~]# subscription-manager subscribe --pool=XYZ01234567
subscribe command are listed in Table 4.4, “subscribe Options”.
list command:
[root@server1 ~]# subscription-manager list --available
+-------------------------------------------+
Available Subscriptions
+-------------------------------------------+
ProductName: RHEL for Physical Servers
ProductId: MKT-rhel-server
PoolId: ff8080812bc382e3012bc3845ca000cb
Quantity: 10
Expires: 2011-09-20--auto option (which is analogous to the --autosubscribe option with the register command).
[root@server1 ~]# subscription-manager subscribe --auto
| Options | Description | Required |
|---|---|---|
| --pool=pool-id | Gives the ID for the subscription to subscribe the machine to. |
Required, unless --auto is used
|
| --auto | Automatically subscribes the system to the best-match subscription or subscriptions. | Optional |
| --quantity | Subscribes multiple counts of an entitlement to the system. This is used to cover subscriptions that define a count limit, like using two 2-socket server subscriptions to cover a 4-socket machine. | Optional |
unsubscribe command with the --all unsubscribes the system from every product and subscription pool it is currently subscribed to.
[root@server1 ~]# subscription-manager unsubscribe --all
unsubscribe command to remove only that product subscription.
cert.pem file or by using the list command. For example:
[root@server1 ~]# subscription-manager list --consumed
+-------------------------------------------+
Consumed Product Subscriptions
+-------------------------------------------+
ProductName: High availability (cluster suite)
ContractNumber: 0
SerialNumber: 11287514358600162
Active: True
Begins: 2010-09-18
Expires: 2011-11-18--serial option to specify the certificate.
[root@server1 ~]# subscription-manager unsubscribe --serial=11287514358600162
--quantity option. The quantity taken applies to the product in the --pool option:
[root@server1 ~]# subscription-manager subscribe --pool=XYZ01234567 --quantity=2
.zip file. Save the file to some kind of portable media, like a flash drive.
certificates.zip file. Unzip the directories until the PEM files for the subscription certificates are available.
import command:
# subscription-manager import --certificate=/tmp/export/entitlement_certificates/596576341785244687.pem --certificate=/tmp/export/entitlement_certificates/3195996649750311162.pem Successfully imported certificate 596576341785244687.pem Successfully imported certificate 3195996649750311162.pem
subscription-manager-gui
.pem file of the product certificate.
subscription-manager-gui
redeem command, with an email address to send the redemption email to when the process is complete.
# subscription-manager redeem --email=jsmith@example.com# subscription-manager redeem --email=jsmith@example.com --org="IT Dept"
list command to display different areas of the subscriptions and products on the system.
| Option | Description |
|---|---|
| --installed (or nothing) |
Lists all of the installed and subscribed product on the system. If no option is given with list, it is the same as using the --installed argument.
|
| --consumed | Lists all of the subscriptions allocated to the system. |
| --available [--all] |
Using --available alone lists all of the compatible, active subscriptions for the system. Using --available --all lists all options, even ones not compatible with the system or with no more available quantities.
|
| --ondate=YYYY-MM-DD |
Shows subscriptions which are active and available on the specified date. This is only used with the --available option. If this is not used, then the command uses the current date.
|
| --installed | Lists all of the products that are installed on the system (and whether they have a subscription) and it lists all of the product subscriptions which are assigned to the system (and whether those products are installed). |
list command shows all of the subscriptions that are currently allocated to the system by using the --consumed option.
[root@server1 ~]# subscription-manager list --consumed
+-------------------------------------------+
Consumed Product Subscriptions
+-------------------------------------------+
ProductName: Red Hat Enterprise Linux Server
ContractNumber: 1458961
SerialNumber: 171286550006020205
Active: True
Begins: 2009-01-01
Expires: 2011-12-31list command shows all of the subscriptions that are compatible with and available to the system using the --available option. To include every subscription the organization has — both the ones that are compatible with the system and others for other platforms — use the --all option with the --available. The --ondate option shows only subscriptions which are active on that date, based on their activation and expiry dates.
[root@server1 ~]# subscription-manager list --available --all
+-------------------------------------------+
Available Subscriptions
+-------------------------------------------+
ProductName: RHEL for Physical Servers
ProductId: MKT-rhel-server
PoolId: ff8080812bc382e3012bc3845ca000cb
Quantity: 10
Expires: 2011-09-20
ProductName: RHEL Workstation
ProductId: MKT-rhel-workstation-mkt
PoolId: 5e09a31f95885cc4
Quantity: 10
Expires: 2011-09-20
[snip]--installed option correlates the products that are actually installed on the system (and their subscription status) and the products which could be installed on the system based on the assigned subscriptions (and whether those products are installed).
[root@server1 ~]# subscription-manager list --installed
+-------------------------------------------+
Installed Product Status
+-------------------------------------------+
ProductName: Red Hat Enterprise Linux
Status: Not Subscribed
Expires:
Subscription:
ContractNumber:
AccountNumber:
ProductName: Awesome OS Server
Status: Not Installed
Expires: 2012-02-20
Subscription: 54129829316535230
ContractNumber: 39
AccountNumber: 12331131231
yum. Subscription Manager has its own yum plug-ins: product-id for subscription-related information for products and subscription-manager which is used for the content repositories.
baseurl parameter of the rhsm.conf file.
# yum install rubygems --enablerepo=rhel-6-server-optional-rpms Loaded plugins:product-id, refresh-packagekit,subscription-managerUpdating Red Hat repositories. ....
yum is described in Chapter 5, Yum.
[root@server ~]# subscription-manager list
+-------------------------------------------+
Installed Product Status
+-------------------------------------------+
ProductName: Red Hat Enterprise Linux Server
Status: Not Subscribed
Expires:
SerialNumber:
ContractNumber:
AccountNumber:
rhsmcertd. This daemon checks the certificate validity dates daily. If a subscription is within 24 hours of expiring, then Subscription Manager will check for any available compatible subscriptions and automatically re-subscribes the system, much like auto-subscribing during registration.
autoheal parameter to the Subscription Manager configuration.
vim /etc/rhsm/rhsm.conf
[rhsmcertd] area, add the autoheal line, and set the value to true.
[rhsmcertd]
certFrequency = 240
healFrequency = 1440
autoheal = trueconfig command:
[root@server1 ~]# subscription-manager config --rhsmcertd.autoheal=true
healFrequency parameter to zero means that Subscription Manager simply uses the default time setting.
# vim /etc/rhsm/rhsm.conf
[rhsmcertd] section, set the healFrequency parameter to the time, in minutes, to check for changed subscriptions.
[rhsmcertd] certFrequency = 240 healFrequency = 1440
rhsmcertd daemon to reload the configuration.
# service rhsmcertd start
orgs, environments, and repos commands list the organization, environment, and repository information for the system, depending on the organization and environments it belongs to.
subscription-manager orgs --username=jsmith --password=secret
+-------------------------------------------+
admin Organizations
+-------------------------------------------+
OrgName: Admin Owner
OrgKey: admin
OrgName: Dev East
OrgKey: deveast
OrgName: Dev West
OrgKey: devwest
subscription-manager environments --username=jsmith --password=secret --org=admin
+-------------------------------------------+
Environments
+-------------------------------------------+
Name: Locker
Description: None
Name: Dev
Description:
Name: Prod
Description:
subscription-manager repos --list
+----------------------------------------------------------+
Entitled Repositories in /etc/yum.repos.d/redhat.repo
+----------------------------------------------------------+
RepoName: never-enabled-content
RepoId: never-enabled-content
RepoUrl: https://content.example.com/repos/optional
Enabled: 0
RepoName: always-enabled-content
RepoId: always-enabled-content
RepoUrl: https://content.example.com/repos/dev
Enabled: 1
RepoName: content
RepoId: content-label
RepoUrl: https://content.example.com/repos/prod
Enabled: 1
.pem file.
https://access.redhat.com/
certificates.zip file. Unzip the directories until the PEM files for the entitlement certificates are available.
import command:
# subscription-manager import --certificate=/tmp/export/entitlement_certificates/596576341785244687.pem --certificate=/tmp/export/entitlement_certificates/3195996649750311162.pem Successfully imported certificate 596576341785244687.pem Successfully imported certificate 3195996649750311162.pem
refresh command updates all of the subscription information that is available to the consumer. This removes expired subscriptions and adds new subscriptions to the list. This does not subscribe the machine, but it does pull in the newest data for administrators to use.
[root@server1 ~]# subscription-manager refresh
rhsm.conf configuration file. There are other support files that either influence the Red Hat Subscription Manager service or can help administrators better use the Subscription Manager.
| File or Directory | Description |
|---|---|
| /etc/rhsm | The primary Red Hat Subscription Manager configuration directory. |
| /etc/rhsm/rhsm.conf | The Red Hat Subscription Manager configuration file. This is used by both the GUI and the CLI. |
| /etc/rhsm/facts |
Any user-defined JSON files that override or add system facts to determine entitlement compatibility. Any facts files must end in .facts.
|
| /var/lib/rhsm/cache/installed_products.json | A master list of installed products, which is sent by Subscription Manager to a hosted content service, such as System Engine. |
| /var/lib/rhsm/facts/facts.facts | The default system facts filed, gathered by the Subscription Manager. |
| /var/lib/rhsm/packages/ | The package profile cache (a list of installed products) which is gathered and periodically updated by the Subscription Manager. |
| /var/log/rhsm | The Red Hat Subscription Manager log directory. |
| /var/log/rhsm/rhsm.log | The log for the Red Hat Subscription Manager tools. |
| /var/log/rhsm/rhsmcertd.log |
The log for the Red Hat Subscription Manager daemon, rhsmcertd.
|
| /etc/pki/consumer | The directory which contains the identity certificates used by the system to identify itself to the subscription service. |
| /etc/pki/consumer/cert.pem | The base-64 consumer identity certificate file. |
| /etc/pki/consumer/key.pem | The base-64 consumer identity key file. |
| /etc/pki/entitlement | The directory which contains the entitlement certificates for the available subscriptions. |
/etc/pki/product/product_serial#.pem
| The product certificates for installed software products. |
| /var/run/subsys/rhsm | Runtime files for Red Hat Subscription Manager |
| /etc/init.d/rhsmcertd | The subscription certificate daemon. |
| /etc/cron.daily/rhsm-complianced and /usr/libexec/rhsm-complianced | Files to run daily checks and notifications for subscription validity. |
| /etc/yum/pluginconf.d/rhsmplugin.conf |
The configuration file to include the Red Hat Subscription Manager plug-in in the yum configuration.
|
| /usr/share/rhsm | All of the Python and script files used by both Red Hat Subscription Manager tool to perform subscription tasks. |
| /usr/share/rhsm/gui | All of the Python script and image files used to render the Red Hat Subscription Manager GUI. |
rhsm.conf. This file configures several important aspects of how Red Hat Subscription Manager interacts with both entitlements and content services:
rhsm.conf file is divided into three sections. Two major sections defined the subscription service ([server]) and content and product delivery ([rhsm]). The third section relates to the rhsmcertd daemon. Each assertion is a simple attribute= value pair. Any of the default values can be edited; all possible attributes are present and active in the default rhsm.conf file.
# Red Hat Subscription Manager Configuration File: # Unified Entitlement Platform Configuration [server] # Server hostname: hostname = subscription.rhn.redhat.com # Server prefix: prefix = /subscription # Server port: port = 443 # Set to 1 to disable certificate validation: insecure = 0 # Set the depth of certs which should be checked # when validating a certificate ssl_verify_depth = 3 # Server CA certificate location: ca_cert_dir = /etc/rhsm/ca/ # an http proxy server to use proxy_hostname = # port for http proxy server proxy_port = # user name for authenticating to an http proxy, if needed proxy_user = # password for basic http proxy auth, if needed proxy_password = [rhsm] # Content base URL: baseurl= https://cdn.redhat.com # Default CA cert to use when generating yum repo configs: repo_ca_cert = %(ca_cert_dir)sredhat-uep.pem # Where the certificates should be stored productCertDir = /etc/pki/product entitlementCertDir = /etc/pki/entitlement consumerCertDir = /etc/pki/consumer [rhsmcertd] # Frequency of certificate refresh (in minutes): certFrequency = 240 # Frequency of autoheal check (1440 min = 1 day): healFrequency = 1440
| Parameter | Description | Default Value |
|---|---|---|
| [server] Parameters | ||
| hostname | Gives the IP address or fully-qualified domain name of the subscription service. | subscription.rhn.redhat.com |
| prefix | Gives the directory, in the URL, to use to connect to the subscription service. | /subscription |
| port | Gives the port to use to connect to the subscription service. | 443 |
| insecure | Sets whether to use a secure (0) or insecure (1) connection for connections between the Subscription Manager clients and the subscription service. | 0 |
| ssl_verify_depth | Sets how far back in the certificate chain to verify the certificate. | 3 |
| proxy_hostname | Gives the hostname of the proxy server. This is required. | |
| proxy_port | Gives the port of the proxy server. This is required. | |
| proxy_user | Gives the user account to use to access the proxy server. This may not be required, depending on the proxy server configuration. | |
| proxy_password | Gives the password credentials to access the proxy server. This may not be required, depending on the proxy server configuration. | |
| ca_cert_dir | Gives the location for the CA certificate for the CA which issued the subscription service's certificates. This allows the client to identify and trust the subscription service for authentication for establishing an SSL connection. | /etc/rhsm/ca |
| [rhsm] Parameters | ||
| baseurl | Gives the full URL to access the content delivery system. | https://cdn.redhat.com |
| repo_ca_cert | Identifies the default CA certificate to use to set the yum repo configuration. | %(ca_cert_dir)sredhat-uep.pem |
| showIncompatiblePools |
Sets whether to display subscription pools which are not compatible with the system's architecture but which have been purchased by an organization. By default, Subscription Manager only displays subscriptions which are compatible with, and therefore available to, the system.
This parameter only applies to the Subscription Manager GUI. Incompatible subscriptions can be displayed in the CLI by using the
--all option with the list command.
| 0 |
| productCertDir | Sets the root directory where the product certificates are stored and can be accessed by Subscription Manager. | /etc/pki/product |
| consumerCertDir | Sets the directory where the identity certificate for the system is stored and can be accessed by Subscription Manager. | /etc/pki/consumer |
| entitlementCertDir | Sets the directory where the entitlement certificates for the system are stored and can be accessed by Subscription Manager. Each subscription has its own entitlement certificate. | /etc/pki/entitlement |
| [rhsmcertd] Parameters | ||
| certFrequency | Sets the interval, in minutes, to check and update entitlement certificates used by Subscription Manager. | 240 |
| healFrequency | Sets the interval, in minutes, to check for change subscriptions and installed products and to allocate subscriptions, as necessary, to maintain subscription status for all products. | 240 |
subscription-manager has a subcommand that can change the rhsm.conf configuration file. Almost all of the connection information used by Subscription Manager to access the subscription server, content server, and any proxies is set in the configuration file, as well as general configuration parameters like the frequency Subscription Manager checks for entitlements updates. There are major divisions in the rhsm.conf file, such as [server] which is used to configure the subscription server. When changing the Subscription Manager configuration, the settings are identified with the format section.parameter and then the new value. For example:
server.hostname=newsubscription.example.com
config command:
[root@server1 ~]# subscription-manager config --section.parameter=newValue
[root@server1 ~]# subscription-manager config --server.hostname=subscription.example.com
rhsm.conf file parameters are listed in Table 4.7, “rhsm.conf Parameters”. This is most commonly used to change connection settings:
config command also has a --remove option. This deletes the the current value for the parameter without supplying a new parameter. A blank value tells Subscription Manager to use any default values that are set for that parameter rather than a user-defined value. For example:
[root@server1 ~]# subscription-manager config --remove=rhsm.certFrequency The default value for rhsm.certFrequency will now be used.
[root@server1 ~]# subscription-manager config --remove=server.proxy You have removed the value in section server for parameter proxy.
subscription-manager-gui
rhsm.conf file; this is the same as configuring it in the Subscription Manager GUI. The proxy configuration is stored and used for every connection between the subscription service and the local system.
vim /etc/rhsm/rhsm.conf
[server] section that relate to the HTTP proxy. All parameters are described in Table 4.7, “rhsm.conf Parameters”. There are four parameters directly related to the proxy:
proxy_hostname for the IP address or fully-qualified domain name of the proxy server; this is required.
proxy_hostname argument blank means that no HTTP proxy is used.
proxy_port for the proxy server port.
proxy_user for the user account to connect to the proxy; this may not be required, depending on the proxy server's configuration.
proxy_password for the password for the user account to connect to the proxy; this may not be required, depending on the proxy server's configuration.
[server] # an http proxy server to use proxy_hostname = proxy.example.com # port for http proxy server proxy_port = 443 # user name for authenticating to an http proxy, if needed proxy_user = # password for basic http proxy auth, if needed proxy_password =
subscription-manager.
| Argument | Description | Required for a Proxy Connection? |
|---|---|---|
| --proxy | Gives the proxy server to connect to, in the format hostname:port. | Yes |
| --proxyuser | Gives the username to use to authenticate. This is only required if user authentication is required. | No |
| --proxypass | Gives the password to use with the user account. This is only required if user authentication is required. | No |
subscription-manager operation. For example:
[root@server1 ~]# subscription-manager subscribe --pool=ff8080812bc382e3012bc3845ca000cb --proxy=proxy.example.com:8443 --proxyuser=jsmith --proxypass=secret
rhsm.conf file. The subscription service connection settings are in the [server] section of the configuration file.
vim /etc/rhsm/rhsm.conf
[server] section that relate to the subscription service connection. All parameters are described in Table 4.7, “rhsm.conf Parameters”. There are three parameters directly related to the connection:
hostname for the IP address or fully-qualified domain name of the machine
prefix for the subscription service directory
port for the subscription service port
[server] hostname=entitlements.server.example.com prefix=/candlepin port=8443
vim /etc/rhsm/rhsm.conf
baseurl directive in the [rhsm] section. This is the full URL to the service.
[rhsm] # Content base URL: baseurl= http://content.example.com/content
vim /etc/rhsm/rhsm.conf
[server] section that relate to a secure connection. All parameters are described in Table 4.7, “rhsm.conf Parameters”. There are three parameters directly related to the connection:
insecure to set whether to use a secure (0) or insecure (1) connection
ca_cert_dir for the directory location for the CA certificate for authentication and verification
port for the subscription service port; this should be an SSL port if a secure connection is required
[server]
port=8443
insecure = 1
ca_cert = /etc/rhsm/carhsmcertd, runs as a service on the system. The daemon, by default, starts with the system, and it can be started, stopped, or checked with the service command.
service rhsmcertd status rhsmcertd (pid 13084) is running...
chkconfig also defines startup settings for different run levels of the server.
chkconfig. By default, the Red Hat Subscription Manager daemon, rhsmcertd, is configured to run at levels 3, 4, and 5, so that the service is started automatically when the server reboots.
chkconfig. For example, to enable run level 2:
chkconfig --level 2345 rhsmcertd on
rhsmcertd from the start list, change the run level settings off:
chkconfig --level 2345 rhsmcertd off
service and chkconfig settings.
system-config-services package must be installed for the wizard to be available.
rhsmcertd item in the list of services on the left, and then edit the service as desired.
/var/log/rhsm directory:
rhsm.log shows every invocation and result of running the Subscription Manager GUI or CLI
rhsmcertd.log shows every time a new certificate is generated, which happens on a schedule defined by the certFrequency parameter in the rhsm.conf file.
rhsm.log log contains the sequence of every Python call for every operation invoked through the Subscription Manager tools. Each entry has this format:
YYYY-MM-DD HH:MM:SS,process_id [MESSAGE_TYPE] call python_script response
rhsm.log relates to the Python script or function that was called, there can be multiple log entries for a single operation.
2010-10-01 17:27:57,874 [INFO] _request() @connection.py:97 - status code: 200 2010-10-01 17:27:57,875 [INFO] perform() @certlib.py:132 - updated: Total updates: 0 Found (local) serial# [] Expected (UEP) serial# [] Added (new) <NONE> Deleted (rogue): <NONE> Expired (not deleted): <NONE> Expired (deleted): <NONE> 2010-10-01 17:27:57,878 [INFO] __init__() @connection.py:193 - Using certificate authentication: key = /etc/pki/consumer/key.pem, cert = /etc/pki/consumer/cert.pem, ca = /etc/pki/CA/candlepin.pem, insecure = True 2010-10-01 17:27:57,878 [INFO] __init__() @connection.py:196 - Connection Established: host: candlepin1.devlab.phx1.redhat.com, port: 443, handler: /candlepin
rhsmcertd.log file are much simpler. The log only records when the rhsmcertd daemon starts or stops and every time a certificate is updated.
Fri Oct 1 13:27:44 2010: started: interval = 240 minutes Fri Oct 1 13:27:50 2010: certificates updated
--all option:
[root@server1 ~]# subscription-manager list --available --all
rhsm.conf configuration file.
vim /etc/rhsm/rhsm.conf
showIncompatiblePools directive in the [rhsm] section. A value of 0 shows only compatible entitlements.
[rhsm]
# Content base URL:
showIncompatiblePools = 1/etc/redhat-release or /etc/sysconfig. In both the Red Hat Subscription Manager GUI and CLI, the facts are represented as simple attribute: value pairs.
subscription-manager-gui
facts with the --list option.
[root@server1 ~]# subscription-manager facts --list cpu.architecture: i686 cpu.core(s)_per_socket: 4 cpu.cpu(s): 4 cpu.cpu_family: 6 cpu.cpu_mhz: 2000.010 cpu.cpu_op-mode(s): 32-bit, 64-bit cpu.cpu_socket(s): 1 cpu.l1d_cache: 32K cpu.l1i_cache: 32K cpu.l2_cache: 6144K cpu.model: 23 cpu.stepping: 6 cpu.thread(s)_per_core: 1 cpu.vendor_id: GenuineIntel cpu.virtualization: VT-x distribution.id: Santiago distribution.name: Red Hat Enterprise Linux Workstation distribution.version: 6 dmi.baseboard.manufacturer: IBM dmi.baseboard.product_name: Server Blade ... [snip] ...
--update option with the facts command.
[root@server1 ~]# subscription-manager facts --update
/var/lib/rhsm/facts/facts.facts. These facts are stored as attribute: value pairs, in a comma-separated list.
{"fact1": "value1","fact2": "value2"}/etc/rhsm/facts directory. These JSON files can override existing facts or even add new facts to be used by the subscription service.
vim /etc/rhsm/facts/my-example.facts {"uname.machine": "x86","kernel_version": "2.6.32","physical_location": "MTV colo rack 5"}
identity command. Although not required, using the --force option will require the username and password and will cause the Subscription Manager to prompt for the credentials if they are not passed in the command:
[root@server1 ~]# subscription-manager identity --regenerate --force Username: jsmith@example.com Password: Identity certificate has been regenerated.
identity command to return the current UUID. The UUID is the Current identity is value.
[root@server1 ~]# subscription-manager identity Current identity is: 63701087-f625-4519-8ab2-633bb50cb261 name: server1.example.com org name: 6340056 org id: 8a85f981302cbaf201302d89931e059a
list --installed command with the command-line tools.
rhsmcertd, checks the system periodically — once when it is first registered and then when it runs a refresh operation every four hours — to get the most current list of installed products. When the system is registered and then whenever there is a change to the package list, Subscription Manager sends an updated package profile to the subscription service.
/var/lib/rhsm/packages/.
subscription-manager script. Information like the consumer ID or subscription pool ID is pulled up and referenced automatically in the Red Hat Subscription Manager UI, but it has to be entered manually in the command line.
| Information | Description | Operations Used In | Find It In ... |
|---|---|---|---|
| Consumer ID | A unique identifier for each system that is registered to the subscription service. | identity |
The simplest method is to use the identity command to return the current UUID.
[root@server1 ~]# subscription-manager identity Current identity is: 63701087-f625-4519-8ab2-633bb50cb261 name: consumer-1.example.com org name: 6340056 org id: 8a85f981302cbaf201302d89931e059aThe Subject CN element of the identity certificate for the system, /etc/pki/consumer/cert.pem. The UUID can also be returned by using openssl to pretty-print the certificate.
openssl x509 -text -in /etc/pki/consumer/cert.pem Certificate: ... snip ... Subject: CN=7d133d55 876f 4f47 83eb 0ee931cb0a97 |
| Pool ID | An identifier for a specific set of subscriptions. This set is created when subscriptions are purchased. Whenever a system needs to subscribe to a product, it references a pool ID to identify which purchased set of subscriptions to use. | subscribe |
The PoolID value given for a product when listing available subscriptions. For example:
[root@server1 ~]# subscription-manager list --available +----------------------+ Available Subscriptions +----------------------+ ProductName: Red Hat Enterprise Linux, Standard (up to 2 sockets) 3 year ProductId: MCT0346F3 PoolId: ff8080812bc382e3012bc3845ca000cb Quantity: 2 Expires: 2011-02-28 |
| Product certificate serial number | The identification used for a specific, installed product. A certificate with a unique serial number is generated when a product is installed; this serial number is used to identify that specific product installation when managing subscriptions. | unsubscribe |
The SerialNumber line in the product subscription information. This can be returned by running list --consumed.
[root@server1 ~]# subscription-manager list --consumed +-----------------------------+ Consumed Product Subscriptions +-----------------------------+ ProductName: High availability (cluster suite) ContractNumber: 0 SerialNumber: 11287514358600162 .... |
| Product ID | The internal identifier used to identify a type of product. |
The ProductID value given for a product when listing available subscriptions. For example:
[root@server1 ~]# subscription-manager list --available +----------------------+ Available Subscriptions +----------------------+ ProductName: RHEL for Physical Servers ProductId: MKT-rhel-server ... snip ... |
.pem formatted file. This file format stores both keys and certificates in a base-64 blob. For example:
-----BEGIN CERTIFICATE----- MIIDaTCCAtKgAwIBAgICBZYwDQYJKoZIhvcNAQEFBQAwSzEqMCgGA1UEAxMhY2Fu ZGxlcGluMS5kZXZsYWIucGh4MS5yZWRoYXQuY29tMQswCQYDVQQGEwJVUzEQMA4G A1UEBxMHUmFsZWlnaDAeFw0xMDEwMDYxNjMyMDVaFw0xMTEwMDYyMzU5NTlaMC8x LTArBgNVBAMMJDQ4ODFiZDJmLTg2OGItNDM4Yy1hZjk2LThiMWQyODNkYWZmYzCC ASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAKNyLw6+IMtjY03F7Otxj2GL GTz5VKx1kfWY7q4OD4w+XlBHTkt+2tQV9S+4TFkUZ7XoI80LDL/BONpy/gq5c5cw yKvjv2gjSS/pihgYNXc5zUOIfSj1vb3fHGHOkzdCcZMyWq1z0N/zaLClp/zP/pcM og4NTAg2niNPjFYvkQ+oIl16WmQpefM0y0SY7N7oJd2T8dZjOiuLV2cVZLfwjrwG 9UpkT2J03g+n1ZA9q95ibLD5NVOdTy9+2lfRhdDViZaVoFiQXvg86qBHQ0ieENuF a6bCvGgpTxcBuVXmsnl2+9dnMiwoDqPZp1HB6G2uNmyNe/IvkTOPFJ/ZVbtBTYUC AwEAAaOB8zCB8DARBglghkgBhvhCAQEEBAMCBaAwCwYDVR0PBAQDAgSwMHsGA1Ud IwR0MHKAFGiY1N2UtulxcMFy0j6gQGLTyo6CoU+kTTBLMSowKAYDVQQDEyFjYW5k bGVwaW4xLmRldmxhYi5waHgxLnJlZGhhdC5jb20xCzAJBgNVBAYTAlVTMRAwDgYD VQQHEwdSYWxlaWdoggkA1s54sVacN0EwHQYDVR0OBBYEFGbB5fqOzh32g4Wqrwhc /96IupIgMBMGA1UdJQQMMAoGCCsGAQUFBwMCMB0GA1UdEQQWMBSkEjAQMQ4wDAYD VQQDDAV4ZW9wczANBgkqhkiG9w0BAQUFAAOBgQANxHRsev4fYfnHO9kYcHo4UeK7 owN+fq92gl76iRHRnhzkPlhWL+uV2tyqGG9zJASOX+qEDOqN5sVAB4iNQTDGiUbK z757igD2hsQ4ewv9Vq3QtnajWnfdaUZH919GgWs09Etg6ucsKwgfx1fqjSRLBbOo lZuvBTYROOX6W2vKXw== -----END CERTIFICATE-----
openssl or pk12util can be used to extract and view information from these certificates, in a pretty-print format. The product- and subscription-related information is extracted and viewable in the Red Hat Subscription Manager GUI or command-line tools.
| Certificate Type | Description | Default Location |
|---|---|---|
| Consumer Identity Certificate | Used to identify the system (consumer) to the subscription service. This contains a unique ID which is assigned to the system when it is registered to the system. The identity certificate itself is generated by the subscription service when the system is registered and then sent to the consumer. | /etc/pki/consumer |
| Entitlement Certificate | Contains a list of products that are available to a system to install, based on the subscriptions that the system has been subscribed to. The entitlement certificate defines the software products, the content delivery location, and validity dates. The presence of an entitlement certificate means that the system has consumed one of the quantities from the subscription. | /etc/pki/entitlement |
| Product Certificate | Contains the information about a product after it has been installed. |
/etc/pki/product/product_serial#.pem
|
| CA Certificate | A certificate for the certificate authority which issued the SSL server certificate used by the subscription service. This must be installed on a system for the system to use SSl to connect to the subscription service. | /etc/rhsm/ca/candlepin-ca.pem |
| Satellite Certificate | An XML-formatted certificate which contains a product list. This is used by local Satellite 5.x systems, not the newer subscription service. |
Certificate:
Data:
Version: 3 (0x2)
Serial Number: 1430 (0x596)
Signature Algorithm: sha1WithRSAEncryption
Issuer: CN=entitlement.server.example.com, C=US, L=Raleigh
Validity
Not Before: Oct 6 16:32:05 2010 GMT
Not After : Oct 6 23:59:59 2011 GMT
Subject: CN=4881bd2f-868b-438c-af96-8b1d283daffc
Subject Public Key Info:
Public Key Algorithm: rsaEncryption
Public-Key: (2048 bit)
Modulus:
00:a3:72:2f:0e:be:20:cb:63:63:4d:c5:ec:eb:71:
8f:61:8b:19:3c:f9:54:ac:75:91:f5:98:ee:ae:0e:
0f:8c:3e:5e:50:47:4e:4b:7e:da:d4:15:f5:2f:b8:
4c:59:14:67:b5:e8:23:cd:0b:0c:bf:c1:38:da:72:
fe:0a:b9:73:97:30:c8:ab:e3:bf:68:23:49:2f:e9:
8a:18:18:35:77:39:cd:43:88:7d:28:f5:bd:bd:df:
1c:61:ce:93:37:42:71:93:32:5a:ad:73:d0:df:f3:
68:b0:a5:a7:fc:cf:fe:97:0c:a2:0e:0d:4c:08:36:
9e:23:4f:8c:56:2f:91:0f:a8:22:5d:7a:5a:64:29:
79:f3:34:cb:44:98:ec:de:e8:25:dd:93:f1:d6:63:
3a:2b:8b:57:67:15:64:b7:f0:8e:bc:06:f5:4a:64:
4f:62:74:de:0f:a7:d5:90:3d:ab:de:62:6c:b0:f9:
35:53:9d:4f:2f:7e:da:57:d1:85:d0:d5:89:96:95:
a0:58:90:5e:f8:3c:ea:a0:47:43:48:9e:10:db:85:
6b:a6:c2:bc:68:29:4f:17:01:b9:55:e6:b2:79:76:
fb:d7:67:32:2c:28:0e:a3:d9:a7:51:c1:e8:6d:ae:
36:6c:8d:7b:f2:2f:91:33:8f:14:9f:d9:55:bb:41:
4d:85
Exponent: 65537 (0x10001)
X509v3 extensions:
Netscape Cert Type:
SSL Client, S/MIME
X509v3 Key Usage:
Digital Signature, Key Encipherment, Data Encipherment
X509v3 Authority Key Identifier:
keyid:68:98:D4:DD:94:B6:E9:71:70:C1:72:D2:3E:A0:40:62:D3:CA:8E:82
DirName:/CN=entitlement.server.example.com/C=US/L=Raleigh
serial:D6:CE:78:B1:56:9C:37:41
X509v3 Subject Key Identifier:
66:C1:E5:FA:8E:CE:1D:F6:83:85:AA:AF:08:5C:FF:DE:88:BA:92:20
X509v3 Extended Key Usage:
TLS Web Client Authentication
X509v3 Subject Alternative Name:
DirName:/CN=admin-example
Signature Algorithm: sha1WithRSAEncryption
0d:c4:74:6c:7a:fe:1f:61:f9:c7:3b:d9:18:70:7a:38:51:e2:
bb:a3:03:7e:7e:af:76:82:5e:fa:89:11:d1:9e:1c:e4:3e:58:
56:2f:eb:95:da:dc:aa:18:6f:73:24:04:8e:5f:ea:84:0c:ea:
8d:e6:c5:40:07:88:8d:41:30:c6:89:46:ca:cf:be:7b:8a:00:
f6:86:c4:38:7b:0b:fd:56:ad:d0:b6:76:a3:5a:77:dd:69:46:
47:f7:5f:46:81:6b:34:f4:4b:60:ea:e7:2c:2b:08:1f:c7:57:
ea:8d:24:4b:05:b3:a8:95:9b:af:05:36:11:38:e5:fa:5b:6b:
ca:5f*.pem file stored in the entitlement certificates directory, /etc/pki/entitlement. The name of the *.pem file is a generated numeric identifier that is generated by the subscription service. This ID is an inventory number that is used to associate a subscription quantity with the system in the software inventory.
Certificate:
Data:
Version: 3 (0x2)
Serial Number:
3c:da:6c:06:90:7f:ff
Signature Algorithm: sha1WithRSAEncryption
Issuer: CN=candlepin1.devlab.phx1.redhat.com, C=US, L=Raleigh
Validity
Not Before: Oct 8 17:55:28 2010 GMT
Not After : Oct 2 23:59:59 2011 GMT
Subject: CN=8a878c912b875189012b8cfbc3f2264a
... [snip] ...1.3.6.1.4.1.2312.9.2.product_#.config_#: ..config_value
2 indicates that it is a product entry. product_# is a unique ID which identifies the specific product or variant. config_# relates to the installation information for that product, like its content server or the quantity available.
1.3.6.1.4.1.2312.9. The subsequent numbers identify different subscription areas:
.2. is the product-specific information
.1. is the subscription information
.4. contains the contract information, like its ID number and start and end dates
.5. contains the consumer information, like the consumer ID which installed a product
content repository type
1.3.6.1.4.1.2312.9.2.30393.1:
..yum
product
1.3.6.1.4.1.2312.9.2.30393.1.1:
.HRed Hat Enterprise Linux High Availability (for RHEL Entitlement) (RPMs)
channel name
1.3.6.1.4.1.2312.9.2.30393.1.2:
.Dred-hat-enterprise-linux-high-availability-for-rhel-entitlement-rpms
vendor
1.3.6.1.4.1.2312.9.2.30393.1.5:
..Red Hat
download URL
1.3.6.1.4.1.2312.9.2.30393.1.6:
.Q/content/dist/rhel/entitlement/releases/$releasever/$basearch/highavailability/os
key download URL
1.3.6.1.4.1.2312.9.2.30393.1.7:
.2file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release
flex quantity
1.3.6.1.4.1.2312.9.2.30393.1.4:
..0
quantity
1.3.6.1.4.1.2312.9.2.30393.1.3:
..25
repo enabled setting
1.3.6.1.4.1.2312.9.2.30393.1.8:
..1*.pem file stored in the entitlement certificates directory, /etc/pki/product/product_serial#.pem. The name of the *.pem file is a generated numeric identifier that is generated by the subscription service. As with entitlement tracking, the generated ID is an inventory number, used to track installed products and associate them with systems within the subscription service.
<rhn-cert-field name="configuration_area">value</rhn-cert-field>
name argument identifies what entity is being configured. This can be the organization which ordered the subscription (name="owner"), the start and end dates for the entitlement (name="issued" and name="expires"), or the entitlement itself. A system entitlement uses the name argument to set the service being entitled; every content entitlement is set as a name="channel-family" type, with the specific product identified in an additional family argument.
name argument, while the value is between the tags. The last lines of the certificate also set metadata for the subscription, including the version of the Satellite and the signature that signs the XML document (and allows the XML file to be used as a certificate).
<rhn-cert-field name="product">RHN-SATELLITE-001</rhn-cert-field> <rhn-cert-field name="owner">Example Corp</rhn-cert-field> <rhn-cert-field name="issued">2009-04-07 10:18:33</rhn-cert-field> <rhn-cert-field name="expires">2009-11-25 00:00:00</rhn-cert-field> ... [snip] ... <rhn-cert-field name="satellite-version">5.3</rhn-cert-field> <rhn-cert-field name="generation">2</rhn-cert-field> <rhn-cert-signature> -----BEGIN PGP SIGNATURE----- Version: Crypt::OpenPGP 1.03 iQBGBAARAwAGBQJJ22C+AAoJEJ5ynaAAAAkyyZ0An18+4hK5Ozt4HWieFvahsTnF aPcaAJ0e5neOfdDZRLOgDE+Tp/Im3Hc3Rg== =gqP7 -----END PGP SIGNATURE----- </rhn-cert-signature>
name="slot" field lists how many total systems are allowed to use this Satellite certificate to receive content. It is a global quantity.
<rhn-cert-field name="slots">119</rhn-cert-field>
name argument and then setting the quantity as the value within the tags.
<rhn-cert-field name="provisioning-slots">117</rhn-cert-field> <rhn-cert-field name="monitoring-slots">20</rhn-cert-field> <rhn-cert-field name="virtualization_host">67</rhn-cert-field>
rhel-server family, while a specific Virtualization Server subscription provides an additional rhel-server-vt family..
<rhn-cert-field name="channel-families" quantity="95" family="rhel-server"/> <rhn-cert-field name="channel-families" quantity="67" family="rhel-server-vt"/>
rhel-* family, because that refers to the platform the product is supported on. In this example, Red Hat Directory Server is in the rhel-rhdirserv family.
<rhn-cert-field name="channel-families" quantity="3" family="rhel-rhdirserv"/>
<rhn-cert-field name="channel-families" quantity="212" family="rhn-tools"/>
yum to install, update or remove packages on your system. All examples in this chapter assume that you have already obtained superuser privileges by using either the su or sudo command.
yumcheck-update
~]# yum check-update
Loaded plugins: product-id, refresh-packagekit, subscription-manager
Updating Red Hat repositories.
INFO:rhsm-app.repolib:repos updated: 0
PackageKit.x86_64 0.5.8-2.el6 rhel
PackageKit-glib.x86_64 0.5.8-2.el6 rhel
PackageKit-yum.x86_64 0.5.8-2.el6 rhel
PackageKit-yum-plugin.x86_64 0.5.8-2.el6 rhel
glibc.x86_64 2.11.90-20.el6 rhel
glibc-common.x86_64 2.10.90-22 rhel
kernel.x86_64 2.6.31-14.el6 rhel
kernel-firmware.noarch 2.6.31-14.el6 rhel
rpm.x86_64 4.7.1-5.el6 rhel
rpm-libs.x86_64 4.7.1-5.el6 rhel
rpm-python.x86_64 4.7.1-5.el6 rhel
udev.x86_64 147-2.15.el6 rhel
yum.noarch 3.2.24-4.el6 rhelPackageKit — the name of the package
x86_64 — the CPU architecture the package was built for
0.5.8 — the version of the updated package to be installed
rhel — the repository in which the updated package is located
yum and rpm packages), as well as their dependencies (such as the kernel-firmware, rpm-libs, and rpm-python packages), all using yum.
root:
yumupdatepackage_name
~]# yum update udev
Loaded plugins: product-id, refresh-packagekit, subscription-manager
Updating Red Hat repositories.
INFO:rhsm-app.repolib:repos updated: 0
Setting up Update Process
Resolving Dependencies
--> Running transaction check
---> Package udev.x86_64 0:147-2.15.el6 set to be updated
--> Finished Dependency Resolution
Dependencies Resolved
===========================================================================
Package Arch Version Repository Size
===========================================================================
Updating:
udev x86_64 147-2.15.el6 rhel 337 k
Transaction Summary
===========================================================================
Install 0 Package(s)
Upgrade 1 Package(s)
Total download size: 337 k
Is this ok [y/N]:Loaded plugins: product-id, refresh-packagekit, subscription-manager — yum always informs you which Yum plug-ins are installed and enabled. Here, yum is using the product-id, refresh-packagekit, and subscription-manager plug-ins. Refer to Section 5.4, “Yum Plug-ins” for general information on Yum plug-ins, or to Section 5.4.3, “Plug-in Descriptions” for descriptions of specific plug-ins.
udev.x86_64 — you can download and install new udev package.
yum presents the update information and then prompts you as to whether you want it to perform the update; yum runs interactively by default. If you already know which transactions yum plans to perform, you can use the -y option to automatically answer yes to any questions yum may ask (in which case it runs non-interactively). However, you should always examine which changes yum plans to make to the system so that you can easily troubleshoot any problems that might arise.
yum history command as described in Section 5.2.6, “Working with Transaction History”.
yum always installs a new kernel in the same sense that RPM installs a new kernel when you use the command rpm -i kernel. Therefore, you do not need to worry about the distinction between installing and upgrading a kernel package when you use yum: it will do the right thing, regardless of whether you are using the yum update or yum install command.
rpm -i kernel command (which installs a new kernel) instead of rpm -u kernel (which replaces the current kernel). Refer to Section B.2.2, “Installing and Upgrading” for more information on installing/updating kernels with RPM.
yum update (without any arguments):
yum updateyum command with a set of highly-useful security-centric commands, subcommands and options. Refer to Section 5.4.3, “Plug-in Descriptions” for specific information.
yumsearchterm…
~]# yum search meld kompare
Loaded plugins: product-id, refresh-packagekit, subscription-manager
Updating Red Hat repositories.
INFO:rhsm-app.repolib:repos updated: 0
============================ Matched: kompare =============================
kdesdk.x86_64 : The KDE Software Development Kit (SDK)
Warning: No matches found for: meldyum search command is useful for searching for packages you do not know the name of, but for which you know a related term.
yum list and related commands provide information about packages, package groups, and repositories.
* (which expands to match any character multiple times) and ? (which expands to match any one character).
yum command, otherwise the Bash shell will interpret these expressions as pathname expansions, and potentially pass all files in the current directory that match the globs to yum. To make sure the glob expressions are passed to yum as intended, either:
yum list glob_expression… ~]# yum list abrt-addon\* abrt-plugin\*
Loaded plugins: product-id, refresh-packagekit, subscription-manager
Updating Red Hat repositories.
INFO:rhsm-app.repolib:repos updated: 0
Installed Packages
abrt-addon-ccpp.x86_64 1.0.7-5.el6 @rhel
abrt-addon-kerneloops.x86_64 1.0.7-5.el6 @rhel
abrt-addon-python.x86_64 1.0.7-5.el6 @rhel
abrt-plugin-bugzilla.x86_64 1.0.7-5.el6 @rhel
abrt-plugin-logger.x86_64 1.0.7-5.el6 @rhel
abrt-plugin-sosreport.x86_64 1.0.7-5.el6 @rhel
abrt-plugin-ticketuploader.x86_64 1.0.7-5.el6 @rhelyum list all yum list installed ~]# yum list installed "krb?-*"
Loaded plugins: product-id, refresh-packagekit, subscription-manager
Updating Red Hat repositories.
INFO:rhsm-app.repolib:repos updated: 0
Installed Packages
krb5-libs.x86_64 1.8.1-3.el6 @rhel
krb5-workstation.x86_64 1.8.1-3.el6 @rhelyum list available ~]# yum list available gstreamer\*plugin\*
Loaded plugins: product-id, refresh-packagekit, subscription-manager
Updating Red Hat repositories.
INFO:rhsm-app.repolib:repos updated: 0
Available Packages
gstreamer-plugins-bad-free.i686 0.10.17-4.el6 rhel
gstreamer-plugins-base.i686 0.10.26-1.el6 rhel
gstreamer-plugins-base-devel.i686 0.10.26-1.el6 rhel
gstreamer-plugins-base-devel.x86_64 0.10.26-1.el6 rhel
gstreamer-plugins-good.i686 0.10.18-1.el6 rhelyum grouplist yum repolist yuminfopackage_name…
~]# yum info abrt
Loaded plugins: product-id, refresh-packagekit, subscription-manager
Updating Red Hat repositories.
INFO:rhsm-app.repolib:repos updated: 0
Installed Packages
Name : abrt
Arch : x86_64
Version : 1.0.7
Release : 5.el6
Size : 578 k
Repo : installed
From repo : rhel
Summary : Automatic bug detection and reporting tool
URL : https://fedorahosted.org/abrt/
License : GPLv2+
Description: abrt is a tool to help users to detect defects in applications
: and to create a bug report with all informations needed by
: maintainer to fix it. It uses plugin system to extend its
: functionality.yum info package_name command is similar to the rpm -q --info package_name command, but provides as additional information the ID of the Yum repository the RPM package is found in (look for the From repo: line in the output).
yumdbinfopackage_name
user indicates it was installed by the user, and dep means it was brought in as a dependency). For example, to display additional information about the yum package, type:
~]# yumdb info yum
Loaded plugins: product-id, refresh-packagekit, subscription-manager
yum-3.2.27-4.el6.noarch
checksum_data = 23d337ed51a9757bbfbdceb82c4eaca9808ff1009b51e9626d540f44fe95f771
checksum_type = sha256
from_repo = rhel
from_repo_revision = 1298613159
from_repo_timestamp = 1298614288
installed_by = 4294967295
reason = user
releasever = 6.1yumdb command, refer to the yumdb(8) manual page.
yuminstallpackage_name
yuminstallpackage_namepackage_name…
.arch to the package name. For example, to install the sqlite2 package for i586, type:
~]# yum install sqlite2.i586~]# yum install audacious-plugins-\*yum install. If you know the name of the binary you want to install, but not its package name, you can give yum install the path name:
~]# yum install /usr/sbin/namedyum then searches through its package lists, finds the package which provides /usr/sbin/named, if any, and prompts you as to whether you want to install it.
named binary, but you do not know in which bin or sbin directory is the file installed, use the yum provides command with a glob expression:
~]# yum provides "*bin/named"
Loaded plugins: product-id, refresh-packagekit, subscription-manager
Updating Red Hat repositories.
INFO:rhsm-app.repolib:repos updated: 0
32:bind-9.7.0-4.P1.el6.x86_64 : The Berkeley Internet Name Domain (BIND)
: DNS (Domain Name System) server
Repo : rhel
Matched from:
Filename : /usr/sbin/namedyum provides "*/file_name" is a common and useful trick to find the package(s) that contain file_name.
yum grouplist -v command lists the names of all package groups, and, next to each of them, their groupid in parentheses. The groupid is always the term in the last pair of parentheses, such as kde-desktop in the following example:
~]# yum -v grouplist kde\*
Loading "product-id" plugin
Loading "refresh-packagekit" plugin
Loading "subscription-manager" plugin
Updating Red Hat repositories.
INFO:rhsm-app.repolib:repos updated: 0
Config time: 0.123
Yum Version: 3.2.29
Setting up Group Process
Looking for repo options for [rhel]
rpmdb time: 0.001
group time: 1.291
Available Groups:
KDE Desktop (kde-desktop)
Donegroupinstall:
yumgroupinstallgroup_name
yumgroupinstallgroupid
install command if you prepend it with an @-symbol (which tells yum that you want to perform a groupinstall):
yuminstall@group
KDE Desktop group:
~]#yum groupinstall "KDE Desktop"~]#yum groupinstall kde-desktop~]#yum install @kde-desktop
root:
yumremovepackage_name…
~]# yum remove totem rhythmbox sound-juicerinstall, remove can take these arguments:
install syntax:
yumgroupremovegroup
yumremove@group
KDE Desktop group:
~]#yum groupremove "KDE Desktop"~]#yum groupremove kde-desktop~]#yum remove @kde-desktop
yum to remove only those packages which are not required by any other packages or groups by adding the groupremove_leaf_only=1 directive to the [main] section of the /etc/yum.conf configuration file. For more information on this directive, refer to Section 5.3.1, “Setting [main] Options”.
yum history command allows users to review information about a timeline of Yum transactions, the dates and times on when they occurred, the number of packages affected, whether transactions succeeded or were aborted, and if the RPM database was changed between transactions. Additionally, this command can be used to undo or redo certain transactions.
root, either run yum history with no additional arguments, or type the following at a shell prompt:
yumhistorylist
all keyword:
yumhistorylistall
yumhistoryliststart_id..end_id
yumhistorylistglob_expression…
~]# yum history list 1..5
Loaded plugins: product-id, refresh-packagekit, subscription-manager
ID | Login user | Date and time | Action(s) | Altered
-------------------------------------------------------------------------------
5 | Jaromir ... <jhradilek> | 2011-07-29 15:33 | Install | 1
4 | Jaromir ... <jhradilek> | 2011-07-21 15:10 | Install | 1
3 | Jaromir ... <jhradilek> | 2011-07-16 15:27 | I, U | 73
2 | System <unset> | 2011-07-16 15:19 | Update | 1
1 | System <unset> | 2011-07-16 14:38 | Install | 1106
history listyum history list command produce tabular output with each row consisting of the following columns:
ID — an integer value that identifies a particular transaction.
Login user — the name of the user whose login session was used to initiate a transaction. This information is typically presented in the Full Name <username>System <unset> is used instead.
Date and time — the date and time when a transaction was issued.
Action(s) — a list of actions that were performed during a transaction as described in Table 5.1, “Possible values of the Action(s) field”.
Altered — the number of packages that were affected by a transaction, possibly followed by additional information as described in Table 5.2, “Possible values of the Altered field”.
| Action | Abbreviation | Description |
|---|---|---|
Downgrade
|
D
| At least one package has been downgraded to an older version. |
Erase
|
E
| At least one package has been removed. |
Install
|
I
| At least one new package has been installed. |
Obsoleting
|
O
| At least one package has been marked as obsolete. |
Reinstall
|
R
| At least one package has been reinstalled. |
Update
|
U
| At least one package has been updated to a newer version. |
| Symbol | Description |
|---|---|
<
|
Before the transaction finished, the rpmdb database was changed outside Yum.
|
>
|
After the transaction finished, the rpmdb database was changed outside Yum.
|
*
| The transaction failed to finish. |
#
|
The transaction finished successfully, but yum returned a non-zero exit code.
|
E
| The transaction finished successfully, but an error or a warning was displayed. |
P
|
The transaction finished successfully, but problems already existed in the rpmdb database.
|
s
|
The transaction finished successfully, but the --skip-broken command line option was used and certain packages were skipped.
|
root:
yumhistorysummary
yumhistorysummarystart_id..end_id
yum history list command, you can also display a summary of transactions regarding a certain package or packages by supplying a package name or a glob expression:
yumhistorysummaryglob_expression…
~]# yum history summary 1..5
Loaded plugins: product-id, refresh-packagekit, subscription-manager
Login user | Time | Action(s) | Altered
-------------------------------------------------------------------------------
Jaromir ... <jhradilek> | Last day | Install | 1
Jaromir ... <jhradilek> | Last week | Install | 1
Jaromir ... <jhradilek> | Last 2 weeks | I, U | 73
System <unset> | Last 2 weeks | I, U | 1107
history summaryyum history summary command produce simplified tabular output similar to the output of yum history list.
yum history list and yum history summary are oriented towards transactions, and although they allow you to display only transactions related to a given package or packages, they lack important details, such as package versions. To list transactions from the perspective of a package, run the following command as root:
yumhistorypackage-listglob_expression…
~]# yum history package-list subscription-manager\*
Loaded plugins: product-id, refresh-packagekit, subscription-manager
ID | Action(s) | Package
-------------------------------------------------------------------------------
3 | Updated | subscription-manager-0.95.11-1.el6.x86_64
3 | Update | 0.95.17-1.el6_1.x86_64
3 | Updated | subscription-manager-firstboot-0.95.11-1.el6.x86_64
3 | Update | 0.95.17-1.el6_1.x86_64
3 | Updated | subscription-manager-gnome-0.95.11-1.el6.x86_64
3 | Update | 0.95.17-1.el6_1.x86_64
1 | Install | subscription-manager-0.95.11-1.el6.x86_64
1 | Install | subscription-manager-firstboot-0.95.11-1.el6.x86_64
1 | Install | subscription-manager-gnome-0.95.11-1.el6.x86_64
history package-listroot, use the yum history summary command in the following form:
yumhistorysummaryid
root:
yumhistoryinfoid…
id argument is optional and when you omit it, yum automatically uses the last transaction. Note that when specifying more than one transaction, you can also use a range:
yumhistoryinfostart_id..end_id
~]# yum history info 4..5
Loaded plugins: product-id, refresh-packagekit, subscription-manager
Transaction ID : 4..5
Begin time : Thu Jul 21 15:10:46 2011
Begin rpmdb : 1107:0c67c32219c199f92ed8da7572b4c6df64eacd3a
End time : 15:33:15 2011 (22 minutes)
End rpmdb : 1109:1171025bd9b6b5f8db30d063598f590f1c1f3242
User : Jaromir Hradilek <jhradilek>
Return-Code : Success
Command Line : install screen
Command Line : install yum-plugin-fs-snapshot
Transaction performed with:
Installed rpm-4.8.0-16.el6.x86_64
Installed yum-3.2.29-17.el6.noarch
Installed yum-metadata-parser-1.1.2-16.el6.x86_64
Packages Altered:
Install screen-4.0.3-16.el6.x86_64
Install yum-plugin-fs-snapshot-1.1.30-6.el6.noarch
history inforoot:
yumhistoryaddon-infoid
yum history info, when no id is provided, yum automatically uses the latest transaction. Another way to refer to the latest transaction is to use the last keyword:
yumhistoryaddon-infolast
yum history addon-info command would provide the following output:
~]# yum history addon-info 4
Loaded plugins: product-id, refresh-packagekit, subscription-manager
Transaction ID: 4
Available additional history information:
config-main
config-repos
saved_tx
history addon-infoconfig-main — global Yum options that were in use during the transaction. Refer to Section 5.3.1, “Setting [main] Options” for information on how to change global options.
config-repos — options for individual Yum repositories. Refer to Section 5.3.2, “Setting [repository] Options” for information on how to change options for individual repositories.
saved_tx — the data that can be used by the yum load-transaction command in order to repeat the transaction on another machine (see below).
root:
yumhistoryaddon-infoidinformation
yum history command provides means to revert or repeat a selected transaction. To revert a transaction, type the following at a shell prompt as root:
yumhistoryundoid
root, run the following command:
yumhistoryredoid
last keyword to undo or repeat the latest transaction.
yum history undo and yum history redo commands merely revert or repeat the steps that were performed during a transaction: if the transaction installed a new package, the yum history undo command will uninstall it, and vice versa. If possible, this command will also attempt to downgrade all updated packages to their previous version, but these older packages may no longer be available. If you need to be able to restore the system to the state before an update, consider using the fs-snapshot plug-in described in Section 5.4.3, “Plug-in Descriptions”.
root:
yum-qhistoryaddon-infoidsaved_tx>file_name
root:
yumload-transactionfile_name
rpmdb version stored in the file must by identical to the version on the target system. You can verify the rpmdb version by using the yum version nogroups command.
root:
yumhistorynew
/var/lib/yum/history/ directory. The old transaction history will be kept, but will not be accessible as long as a newer database file is present in the directory.
yum and related utilities is located at /etc/yum.conf. This file contains one mandatory [main] section, which allows you to set Yum options that have global effect, and may also contain one or more [repository] sections, which allow you to set repository-specific options. However, best practice is to define individual repositories in new or existing .repo files in the /etc/yum.repos.d/directory. The values you define in the [main] section of the /etc/yum.conf file may override values set in individual [repository] sections.
[main] section of the /etc/yum.conf configuration file;
[repository] sections in /etc/yum.conf and .repo files in the /etc/yum.repos.d/ directory;
/etc/yum.conf and files in the /etc/yum.repos.d/ directory so that dynamic version and architecture values are handled correctly;
/etc/yum.conf configuration file contains exactly one [main] section, and while some of the key-value pairs in this section affect how yum operates, others affect how Yum treats repositories. You can add many additional options under the [main] section heading in /etc/yum.conf.
/etc/yum.conf configuration file can look like this:
[main]
cachedir=/var/cache/yum/$basearch/$releasever
keepcache=0
debuglevel=2
logfile=/var/log/yum.log
exactarch=1
obsoletes=1
gpgcheck=1
plugins=1
installonly_limit=3
[comments abridged]
# PUT YOUR REPOS HERE OR IN separate files named file.repo
# in /etc/yum.repos.d[main] section:
assumeyes=valuevalue is one of:
0 — yum should prompt for confirmation of critical actions it performs. This is the default.
1 — Do not prompt for confirmation of critical yum actions. If assumeyes=1 is set, yum behaves in the same way that the command line option -y does.
cachedir=directorydirectory is an absolute path to the directory where Yum should store its cache and database files. By default, Yum's cache directory is /var/cache/yum/$basearch/$releasever.
$basearch and $releasever Yum variables.
debuglevel=valuevalue is an integer between 1 and 10. Setting a higher debuglevel value causes yum to display more detailed debugging output. debuglevel=0 disables debugging output, while debuglevel=2 is the default.
exactarch=valuevalue is one of:
0 — Do not take into account the exact architecture when updating packages.
1 — Consider the exact architecture when updating packages. With this setting, yum will not install an i686 package to update an i386 package already installed on the system. This is the default.
exclude=package_name [more_package_names]* and ?) are allowed.
gpgcheck=valuevalue is one of:
0 — Disable GPG signature-checking on packages in all repositories, including local package installation.
1 — Enable GPG signature-checking on all packages in all repositories, including local package installation. gpgcheck=1 is the default, and thus all packages' signatures are checked.
[main] section of the /etc/yum.conf file, it sets the GPG-checking rule for all repositories. However, you can also set gpgcheck=value for individual repositories instead; that is, you can enable GPG-checking on one repository while disabling it on another. Setting gpgcheck=value for an individual repository in its corresponding .repo file overrides the default if it is present in /etc/yum.conf.
groupremove_leaf_only=valuevalue is one of:
0 — yum should not check the dependencies of each package when removing a package group. With this setting, yum removes all packages in a package group, regardless of whether those packages are required by other packages or groups. groupremove_leaf_only=0 is the default.
1 — yum should check the dependencies of each package when removing a package group, and remove only those packages which are not not required by any other package or group.
installonlypkgs=space separated list of packagesyum can install, but will never update. Refer to the yum.conf(5) manual page for the list of packages which are install-only by default.
installonlypkgs directive to /etc/yum.conf, you should ensure that you list all of the packages that should be install-only, including any of those listed under the installonlypkgs section of yum.conf(5). In particular, kernel packages should always be listed in installonlypkgs (as they are by default), and installonly_limit should always be set to a value greater than 2 so that a backup kernel is always available in case the default one fails to boot.
installonly_limit=valuevalue is an integer representing the maximum number of versions that can be installed simultaneously for any single package listed in the installonlypkgs directive.
installonlypkgs directive include several different kernel packages, so be aware that changing the value of installonly_limit will also affect the maximum number of installed versions of any single kernel package. The default value listed in /etc/yum.conf is installonly_limit=3, and it is not recommended to decrease this value, particularly below 2.
keepcache=valuevalue is one of:
0 — Do not retain the cache of headers and packages after a successful installation. This is the default.
1 — Retain the cache after a successful installation.
logfile=file_namefile_name is an absolute path to the file in which yum should write its logging output. By default, yum logs to /var/log/yum.log.
multilib_policy=valuevalue is one of:
best — install the best-choice architecture for this system. For example, setting multilib_policy=best on an AMD64 system causes yum to install 64-bit versions of all packages.
all — always install every possible architecture for every package. For example, with multilib_policy set to all on an AMD64 system, yum would install both the i586 and AMD64 versions of a package, if both were available.
obsoletes=valuevalue is one of:
0 — Disable yum's obsoletes processing logic when performing updates.
1 — Enable yum's obsoletes processing logic when performing updates. When one package declares in its spec file that it obsoletes another package, the latter package will be replaced by the former package when the former package is installed. Obsoletes are declared, for example, when a package is renamed. obsoletes=1 the default.
plugins=valuevalue is one of:
0 — Disable all Yum plug-ins globally.
Yum services. In particular, rhnplugin provides support for RHN Classic, and product-id and subscription-manager plug-ins provide support for the certificate-based Content Delivery Network (CDN). Disabling plug-ins globally is provided as a convenience option, and is generally only recommended when diagnosing a potential problem with Yum.
1 — Enable all Yum plug-ins globally. With plugins=1, you can still disable a specific Yum plug-in by setting enabled=0 in that plug-in's configuration file.
reposdir=directorydirectory is an absolute path to the directory where .repo files are located. All .repo files contain repository information (similar to the [repository] sections of /etc/yum.conf). yum collects all repository information from .repo files and the [repository] section of the /etc/yum.conf file to create a master list of repositories to use for transactions. If reposdir is not set, yum uses the default directory /etc/yum.repos.d/.
retries=valuevalue is an integer 0 or greater. This value sets the number of times yum should attempt to retrieve a file before returning an error. Setting this to 0 makes yum retry forever. The default value is 10.
[main] options, refer to the [main] OPTIONS section of the yum.conf(5) manual page.
[repository] sections, where repository is a unique repository ID such as my_personal_repo (spaces are not permitted), allow you to define individual Yum repositories.
[repository] section takes:
[repository] name=repository_namebaseurl=repository_url
[repository] section must contain the following directives:
name=repository_namerepository_name is a human-readable string describing the repository.
baseurl=repository_urlrepository_url is a URL to the directory where the repodata directory of a repository is located:
http://path/to/repo
ftp://path/to/repo
file:///path/to/local/repo
username:password@linkbaseurl link could be specified as http://user:password@www.example.com/repo/.
baseurl=http://path/to/repo/releases/$releasever/server/$basearch/os/
$releasever, $arch, and $basearch variables in URLs. For more information about Yum variables, refer to Section 5.3.3, “Using Yum Variables”.
[repository] directive is the following:
enabled=valuevalue is one of:
0 — Do not include this repository as a package source when performing updates and installs. This is an easy way of quickly turning repositories on and off, which is useful when you desire a single package from a repository that you do not want to enable for updates or installs.
1 — Include this repository as a package source.
--enablerepo=repo_name or --disablerepo=repo_name option to yum, or through the Add/Remove Software window of the PackageKit utility.
[repository] options exist. For a complete list, refer to the [repository] OPTIONS section of the yum.conf(5) manual page.
/etc/yum.repos.d/redhat.repo file:
# # Red Hat Repositories # Managed by (rhsm) subscription-manager # [red-hat-enterprise-linux-scalable-file-system-for-rhel-6-entitlement-rpms] name = Red Hat Enterprise Linux Scalable File System (for RHEL 6 Entitlement) (RPMs) baseurl = https://cdn.redhat.com/content/dist/rhel/entitlement-6/releases/$releasever/$basearch/scalablefilesystem/os enabled = 1 gpgcheck = 1 gpgkey = file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release sslverify = 1 sslcacert = /etc/rhsm/ca/redhat-uep.pem sslclientkey = /etc/pki/entitlement/key.pem sslclientcert = /etc/pki/entitlement/11300387955690106.pem [red-hat-enterprise-linux-scalable-file-system-for-rhel-6-entitlement-source-rpms] name = Red Hat Enterprise Linux Scalable File System (for RHEL 6 Entitlement) (Source RPMs) baseurl = https://cdn.redhat.com/content/dist/rhel/entitlement-6/releases/$releasever/$basearch/scalablefilesystem/source/SRPMS enabled = 0 gpgcheck = 1 gpgkey = file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release sslverify = 1 sslcacert = /etc/rhsm/ca/redhat-uep.pem sslclientkey = /etc/pki/entitlement/key.pem sslclientcert = /etc/pki/entitlement/11300387955690106.pem [red-hat-enterprise-linux-scalable-file-system-for-rhel-6-entitlement-debug-rpms] name = Red Hat Enterprise Linux Scalable File System (for RHEL 6 Entitlement) (Debug RPMs) baseurl = https://cdn.redhat.com/content/dist/rhel/entitlement-6/releases/$releasever/$basearch/scalablefilesystem/debug enabled = 0 gpgcheck = 1 gpgkey = file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release sslverify = 1 sslcacert = /etc/rhsm/ca/redhat-uep.pem sslclientkey = /etc/pki/entitlement/key.pem sslclientcert = /etc/pki/entitlement/11300387955690106.pem
yum commands and in all Yum configuration files (that is, /etc/yum.conf and all .repo files in the /etc/yum.repos.d/ directory):
$releasever$releasever from the distroverpkg=value line in the /etc/yum.conf configuration file. If there is no such line in /etc/yum.conf, then yum infers the correct value by deriving the version number from the redhat-release package.
$archos.uname() function. Valid values for $arch include: i586, i686 and x86_64.
$basearch$basearch to reference the base architecture of the system. For example, i686 and i586 machines both have a base architecture of i386, and AMD64 and Intel64 machines have a base architecture of x86_64.
$YUM0-9/etc/yum.conf for example) and a shell environment variable with the same name does not exist, then the configuration file variable is not replaced.
$” sign) in the /etc/yum/vars/ directory, and add the desired value on its first line.
$osname, create a new file with “Red Hat Enterprise Linux” on the first line and save it as /etc/yum/vars/osname:
~]# echo "Red Hat Enterprise Linux" > /etc/yum/vars/osname.repo files:
name=$osname $releasever
[main] section of the /etc/yum.conf file), run the yum-config-manager with no command line options:
yum-config-manageryum-config-managersection…
yum-config-managerglob_expression…
~]$ yum-config-manager main \*
Loaded plugins: product-id, refresh-packagekit, subscription-manager
================================== main ===================================
[main]
alwaysprompt = True
assumeyes = False
bandwith = 0
bugtracker_url = https://bugzilla.redhat.com/enter_bug.cgi?product=Red%20Hat%20Enterprise%20Linux%206&component=yum
cache = 0
[output truncated]yum-config-manager command.
Red Hat Network, the Red Hat Subscription Manager tools are used to manage repositories in the /etc/yum.repos.d/redhat.repo file. Refer to Chapter 4, Product Subscriptions and Entitlements for more information how to register a system with Red Hat Network and use the Red Hat Subscription Manager tools to manage subscriptions.
[repository] section to the /etc/yum.conf file, or to a .repo file in the /etc/yum.repos.d/ directory. All files with the .repo file extension in this directory are read by yum, and best practice is to define your repositories here instead of in /etc/yum.conf.
.repo file. To add such a repository to your system and enable it, run the following command as root:
yum-config-manager--add-reporepository_url
repository_url is a link to the .repo file. For example, to add a repository located at http://www.example.com/example.repo, type the following at a shell prompt:
~]# yum-config-manager --add-repo http://www.example.com/example.repo
Loaded plugins: product-id, refresh-packagekit, subscription-manager
adding repo from: http://www.example.com/example.repo
grabbing file http://www.example.com/example.repo to /etc/yum.repos.d/example.repo
example.repo | 413 B 00:00
repo saved to /etc/yum.repos.d/example.reporoot:
yum-config-manager--enablerepository…
repository is the unique repository ID (use yum repolist all to list available repository IDs). Alternatively, you can use a glob expression to enable all matching repositories:
yum-config-manager--enableglob_expression…
[example], [example-debuginfo], and [example-source]sections, type:
~]# yum-config-manager --enable example\*
Loaded plugins: product-id, refresh-packagekit, subscription-manager
============================== repo: example ==============================
[example]
bandwidth = 0
base_persistdir = /var/lib/yum/repos/x86_64/6Server
baseurl = http://www.example.com/repo/6Server/x86_64/
cache = 0
cachedir = /var/cache/yum/x86_64/6Server/example
[output truncated]yum-config-manager --enable command displays the current repository configuration.
root:
yum-config-manager--disablerepository…
repository is the unique repository ID (use yum repolist all to list available repository IDs). Similarly to yum-config-manager --enable, you can use a glob expression to disable all matching repositories at the same time:
yum-config-manager--disableglob_expression…
yum-config-manager --disable command displays the current configuration.
~]# yum install createrepo/mnt/local_repo/.
createrepo --database command on that directory:
~]# createrepo --database /mnt/local_repocreaterepo on Red Hat Enterprise Linux 5 to create the package metadata for Red Hat Enterprise Linux 6 packages. The createrepo command relies on rpm to open and inspect the packages, and rpm on Red Hat Enterprise Linux 5 is not able to open the improved Red Hat Enterprise Linux 6 RPM package format.
yum operations.
yum command. For example:
~]# yum info yum
Loaded plugins: product-id, refresh-packagekit, subscription-manager
[output truncated]Loaded plugins are the names you can provide to the --disableplugins=plugin_name option.
plugins= is present in the [main] section of /etc/yum.conf, and that its value is set to 1:
plugins=1
plugins=0.
Yum services. In particular, rhnplugin provides support for RHN Classic, and product-id and subscription-manager plug-ins provide support for the certificate-based Content Delivery Network (CDN). Disabling plug-ins globally is provided as a convenience option, and is generally only recommended when diagnosing a potential problem with Yum.
/etc/yum/pluginconf.d/ directory. You can set plug-in specific options in these files. For example, here is the refresh-packagekit plug-in's refresh-packagekit.conf configuration file:
[main] enabled=1
[main] section (similar to Yum's /etc/yum.conf file) in which there is (or you can place if it is missing) an enabled= option that controls whether the plug-in is enabled when you run yum commands.
enabled=0 in /etc/yum.conf, then all plug-ins are disabled regardless of whether they are enabled in their individual configuration files.
yum command, use the --noplugins option.
yum command, add the --disableplugin=plugin_name option to the command. For example, to disable the presto plug-in while updating a system, type:
~]# yum update --disableplugin=presto--disableplugin= option are the same names listed after the Loaded plugins line in the output of any yum command. You can disable multiple plug-ins by separating their names with commas. In addition, you can match multiple plug-in names or shorten long ones by using glob expressions:
~]# yum update --disableplugin=presto,refresh-pack*yum-plugin-plugin_name package-naming convention, but not always: the package which provides the presto plug-in is named yum-presto, for example. You can install a Yum plug-in in the same way you install other packages. For instance, to install the security plug-in, type the following at a shell prompt:
~]# yum install yum-plugin-security/) must be on an LVM (Logical Volume Manager) or Btrfs volume. To use the fs-snapshot plug-in on an LVM volume, take the following steps:
vgdisplay command in the following form as root:
vgdisplayvolume_group
Free PE / Size line.
root, run the pvcreate command in the following form to initialize a physical volume for use with the Logical Volume Manager:
pvcreatedevice
vgextend command in the following form as root to add the physical volume to the volume group:
vgextendvolume_groupphysical_volume
/etc/yum/pluginconf.d/fs-snapshot.conf, and make the following changes to the [lvm] section:
enabled option to 1:
enabled = 1
#) from the beginning of the lvcreate_size_args line, and adjust the number of logical extents to be allocated for a snapshot. For example, to allocate 80 % of the size of the original logical volume, use:
lvcreate_size_args = -l 80%ORIGIN
fs-snapshot.conf directives” for a complete list of available configuration options.
yum command, and make sure fs-snapshot is included in the list of loaded plug-ins (the Loaded plugins line) before you confirm the changes and proceed with the transaction. The fs-snapshot plug-in displays a line in the following form for each affected logical volume:
fs-snapshot: snapshottingfile_system(/dev/volume_group/logical_volume):logical_volume_yum_timestamp
lvremove command as root:
lvremove/dev/volume_group/logical_volume_yum_timestamp
root, run the command in the following form to merge a snapshot into its original logical volume:
lvconvert--merge/dev/volume_group/logical_volume_yum_timestamp
lvconvert command will inform you that a restart is required in order for the changes to take effect.
root:
rebootyum command, and make sure fs-snapshot is included in the list of loaded plug-ins (the Loaded plugins line) before you confirm the changes and proceed with the transaction. The fs-snapshot plug-in displays a line in the following form for each affected file system:
fs-snapshot: snapshottingfile_system:file_system/yum_timestamp
root:
btrfssubvolumedeletefile_system/yum_timestamp
root:
btrfssubvolumelistfile_system
root, configure the system to mount this snapshot by default:
btrfssubvolumeset-defaultidfile_system
root:
rebootfs-snapshot.conf directives| Section | Directive | Description |
|---|---|---|
[main]
|
enabled=value
|
Allows you to enable or disable the plug-in. The value must be either 1 (enabled), or 0 (disabled). When installed, the plug-in is enabled by default.
|
exclude=list
|
Allows you to exclude certain file systems. The value must be a space-separated list of mount points you do not want to snapshot (for example, /srv /mnt/backup). This option is not included in the configuration file by default.
| |
[lvm]
|
enabled=value
|
Allows you to enable or disable the use of the plug-in on LVM volumes. The value must be either 1 (enabled), or 0 (disabled). This option is disabled by default.
|
lvcreate_size_args=value
|
Allows you to specify the size of a logical volume snapshot. The value must be the -l or -L command line option for the lvcreate utility followed by a valid argument (for example, -l 80%ORIGIN).
|
/etc/yum/pluginconf.d/kabi.conf. Refer to Table 5.4, “Supported kabi.conf directives” for a list of directives that can be used in the [main] section.
kabi.conf directives| Directive | Description |
|---|---|
enabled=value
|
Allows you to enable or disable the plug-in. The value must be either 1 (enabled), or 0 (disabled). When installed, the plug-in is enabled by default.
|
whitelists=directory
|
Allows you to specify the directory in which the files with supported kernel symbols are located. By default, the kabi plug-in uses files provided by the kabi-whitelists package (that is, the /lib/modules/kabi/ directory).
|
enforce=value
|
Allows you to enable or disable enforcing mode. The value must be either 1 (enabled), or 0 (disabled). By default, this option is commented out and the kabi plug-in only displays a warning message.
|
/etc/sysconfig/protected-packages file[1] (which you should create if it does not exist), and protect-packages will extend protection-from-removal to those packages as well.
--override-protection option with an applicable yum command.
yum is run. The refresh-packagekit plug-in is installed by default.
RHN Classic. This allows systems registered with RHN Classic to update and install packages from this system. Note that RHN Classic is only provided for older Red Hat Enterprise Linux systems (that is, Red Hat Enterprise Linux 4.x, Red Hat Enterprise Linux 5.x, and Satellite 5.x) in order to migrate them over to Red Hat Enterprise Linux 6. The rhnplugin is installed by default.
RHN Classic, see Section 4.1.6, “Certificate-based Red Hat Network versus RHN Classic”.
yum with a set of highly-useful security-related commands, subcommands and options.
~]# yum check-update --security
Loaded plugins: product-id, refresh-packagekit, security, subscription-manager
Updating Red Hat repositories.
INFO:rhsm-app.repolib:repos updated: 0
Limiting package lists to security relevant ones
Needed 3 of 7 packages, for security
elinks.x86_64 0.12-0.13.el6 rhel
kernel.x86_64 2.6.30.8-64.el6 rhel
kernel-headers.x86_64 2.6.30.8-64.el6 rhelyum update --security or yum update-minimal --security to update those packages which are affected by security advisories. Both of these commands update all packages on the system for which a security advisory has been issued. yum update-minimal --security updates them to the latest packages which were released as part of a security advisory, while yum update --security will update all packages affected by a security advisory to the latest version of that package available.
yum update-minimal --security will update you to kernel-2.6.30.8-32, and yum update --security will update you to kernel-2.6.30.8-64. Conservative system administrators may want to use update-minimal to reduce the risk incurred by updating packages as much as possible.
yum.
Red Hat Network. This allows systems registered with Red Hat Network to update and install packages from the certificate-based Content Delivery Network. The subscription-manager plug-in is installed by default.
Yum Guides section of the Yum wiki contains more documentation.
.list in the /etc/sysconfig/protected-packages.d/ directory (which you should create if it does not exist), and list packages—one per line—in these files. protect-packages will protect these too.
gpk-update-viewer command at the shell prompt. In the Software Updates window, all available updates are listed along with the names of the packages being updated (minus the .rpm suffix, but including the CPU architecture), a short summary of the package, and, usually, short descriptions of the changes the update provides. Any updates you do not wish to install can be de-selected here by unchecking the checkbox corresponding to the update.
kernel package, then it will prompt you after installation, asking you whether you want to reboot the system and thereby boot into the newly-installed kernel.
gpk-application command at the shell prompt.
name=<My Repository Name> field of all [repository] sections in the /etc/yum.conf configuration file, and in all repository.repo/etc/yum.repos.d/ directory.
enabled=<1 or 0> field in [repository] sections. Checking an unchecked box enables the Yum repository, and unchecking it disables it. Performing either function causes PolicyKit to prompt for superuser authentication to enable or disable the repository. PackageKit actually inserts the enabled=<1 or 0> line into the correct [repository] section if it does not exist, or changes the value if it does. This means that enabling or disabling a repository through the Software Sources window causes that change to persist after closing the window or rebooting the system. The ability to quickly enable and disable repositories based on our needs is a highly-convenient feature of PackageKit.
<package_name>-devel
<package><package>-devel<package>-libs<package>-libs-devel<package>-debuginfocrontabs-1.10-32.1.el6.noarch.rpm) are never filtered out by checking . This filter has no affect on non-multilib systems, such as x86 machines.
screen, a screen manager that allows you to have multiple logins on one terminal, by typing screen at a shell prompt.
gpk-log command at the shell prompt.
packagekitd daemon back end, which communicates with a package manager-specific back end that utilizes Yum to perform the actual transactions, such as installing and removing packages, etc.
| Window Title | Function | How to Open | Shell Command |
|---|---|---|---|
| Add/Remove Software | Install, remove or view package info |
From the GNOME panel: → →
| gpk-application |
| Software Update | Perform package updates |
From the GNOME panel: → →
| gpk-update-viewer |
| Software Sources | Enable and disable Yum repositories |
From Add/Remove Software: →
| gpk-repo |
| Software Log Viewer | View the transaction log |
From Add/Remove Software: →
| gpk-log |
| Software Update Preferences | Set PackageKit preferences | gpk-prefs | |
| (Notification Area Alert) | Alerts you when updates are available |
From the GNOME panel: → → , the Startup Programs tab
| gpk-update-icon |
packagekitd daemon runs outside the user session and communicates with the various graphical front ends. The packagekitd daemon[2] communicates via the DBus system message bus with another back end, which utilizes Yum's Python API to perform queries and make changes to the system. On Linux systems other than Red Hat and Fedora, packagekitd can communicate with other back ends that are able to utilize the native package manager for that system. This modular architecture provides the abstraction necessary for the graphical interfaces to work with many different package managers to perform essentially the same types of package management tasks. Learning how to use the PackageKit front ends means that you can use the same familiar graphical interface across many different Linux distributions, even when they utilize a native package manager other than Yum.
packagekitd daemon, which runs outside of the user session.
gnome-packagekit package instead of by PackageKit and its dependencies.
pkcon.
service command and can be turned on or off permanently by using the chkconfig on or chkconfig offcommands. They can typically be recognized by a “d” appended to their name, such as the packagekitd daemon. Refer to Chapter 9, Services and Daemons for information about system services.
DSL and PPPoE (Point-to-Point over Ethernet). In addition, NetworkManager allows for the configuration of network aliases, static routes, DNS information and VPN connections, as well as many connection-specific parameters. Finally, NetworkManager provides a rich API via D-Bus which allows applications to query and control network configuration and state.
system-config-network after its command line invocation. In Red Hat Enterprise Linux 6, NetworkManager replaces the former Network Administration Tool while providing enhanced functionality, such as user-specific and mobile broadband configuration. It is also possible to configure the network in Red Hat Enterprise Linux 6 by editing interface configuration files; refer to Chapter 8, Network Interfaces for more information.
~]# yum install NetworkManager~]# service NetworkManager status
NetworkManager (pid 1527) is running...
service command will report NetworkManager is stopped if the NetworkManager service is not running. To start it for the current session:
~]# service NetworkManager startchkconfig command to ensure that NetworkManager starts up every time the system boots:
~]# chkconfig NetworkManager on
~]$ nm-applet &
~]$ nm-connection-editor &
/etc/sysconfig/network-scripts/ directory (mainly in ifcfg-<network_type> interface configuration files), user connection settings are stored in the GConf configuration database and the GNOME keyring, and are only available during login sessions for the user who created them. Thus, logging out of the desktop session causes user-specific connections to become unavailable.
/etc/sysconfig/network-scripts/ directory, and to delete the GConf settings from the user's session. Conversely, converting a system to a user-specific connection causes NetworkManager to remove the system-wide configuration files and create the corresponding GConf/GNOME keyring settings.
/etc/sysconfig/network-scripts/ directory. The scripts used to activate and deactivate these network interfaces are also located here. Although the number and type of interface files can differ from system to system, there are three categories of files that exist in this directory:
/etc/hosts127.0.0.1) as localhost.localdomain. For more information, refer to the hosts(5) manual page.
/etc/resolv.conf/etc/sysconfig/network/etc/sysconfig/network-scripts/ifcfg-interface-name/etc/sysconfig/networking/ directory is used by the Network Administration Tool (system-config-network) and its contents should not be edited manually. Using only one method for network configuration is strongly encouraged, due to the risk of configuration deletion. For more information about configuring network interfaces using the Network Administration Tool, refer to Chapter 7, NetworkManager.
ifcfg-name, where name refers to the name of the device that the configuration file controls.
ifcfg-eth0, which controls the first Ethernet network interface card or NIC in the system. In a system with multiple NICs, there are multiple ifcfg-ethX files (where X is a unique number corresponding to a specific interface). Because each device has its own configuration file, an administrator can control how each interface functions individually.
ifcfg-eth0 file for a system using a fixed IP address:
DEVICE=eth0 BOOTPROTO=none ONBOOT=yes NETMASK=255.255.255.0 IPADDR=10.0.1.27 USERCTL=no
ifcfg-eth0 file for an interface using DHCP looks different because IP information is provided by the DHCP server:
DEVICE=eth0 BOOTPROTO=dhcp ONBOOT=yes
system-config-network) is an easy way to make changes to the various network interface configuration files (refer to Chapter 7, NetworkManager for detailed instructions on using this tool).
BONDING_OPTS=parameters/etc/sysconfig/network-scripts/ifcfg-bondN (see Section 8.2.2, “Channel Bonding Interfaces”). These parameters are identical to those used for bonding devices in /sys/class/net/bonding_device/bonding, and the module parameters for the bonding driver as described in bonding Module Directives.
BONDING_OPTS directive in ifcfg-name. Do not specify options for the bonding device in /etc/modprobe.d/bonding.conf, or in the deprecated /etc/modprobe.conf file.
BOOTPROTO=protocolprotocol is one of the following:
none — No boot-time protocol should be used.
bootp — The BOOTP protocol should be used.
dhcp — The DHCP protocol should be used.
BROADCAST=addressaddress is the broadcast address. This directive is deprecated, as the value is calculated automatically with ipcalc.
DEVICE=namename is the name of the physical device (except for dynamically-allocated PPP devices where it is the logical name).
DHCP_HOSTNAME=namename is a short hostname to be sent to the DHCP server. Use this option only if the DHCP server requires the client to specify a hostname before receiving an IP address.
DNS{1,2}=addressaddress is a name server address to be placed in /etc/resolv.conf if the PEERDNS directive is set to yes.
ETHTOOL_OPTS=optionsoptions are any device-specific options supported by ethtool. For example, if you wanted to force 100Mb, full duplex:
ETHTOOL_OPTS="autoneg off speed 100 duplex full"
ETHTOOL_OPTS to set the interface speed and duplex settings. Custom initscripts run outside of the network init script lead to unpredictable results during a post-boot network service restart.
autoneg off option. This needs to be stated first, as the option entries are order-dependent.
GATEWAY=addressaddress is the IP address of the network router or gateway device (if any).
HOTPLUG=answeranswer is one of the following:
yes — This device should be activated when it is hot-plugged (this is the default option).
no — This device should not be activated when it is hot-plugged.
HOTPLUG=no option can be used to prevent a channel bonding interface from being activated when a bonding kernel module is loaded.
HWADDR=MAC-addressMAC-address is the hardware address of the Ethernet device in the form AA:BB:CC:DD:EE:FF. This directive must be used in machines containing more than one NIC to ensure that the interfaces are assigned the correct device names regardless of the configured load order for each NIC's module. This directive should not be used in conjunction with MACADDR.
IPADDR=addressaddress is the IP address.
LINKDELAY=timetime is the number of seconds to wait for link negotiation before configuring the device.
MACADDR=MAC-addressMAC-address is the hardware address of the Ethernet device in the form AA:BB:CC:DD:EE:FF. This directive is used to assign a MAC address to an interface, overriding the one assigned to the physical NIC. This directive should not be used in conjunction with HWADDR.
MASTER=bond-interfacebond-interface is the channel bonding interface to which the Ethernet interface is linked.
SLAVE directive.
NETMASK=maskmask is the netmask value.
NETWORK=addressaddress is the network address. This directive is deprecated, as the value is calculated automatically with ipcalc.
ONBOOT=answeranswer is one of the following:
yes — This device should be activated at boot-time.
no — This device should not be activated at boot-time.
PEERDNS=answeranswer is one of the following:
yes — Modify /etc/resolv.conf if the DNS directive is set. If using DHCP, then yes is the default.
no — Do not modify /etc/resolv.conf.
SLAVE=answeranswer is one of the following:
yes — This device is controlled by the channel bonding interface specified in the MASTER directive.
no — This device is not controlled by the channel bonding interface specified in the MASTER directive.
MASTER directive.
SRCADDR=addressaddress is the specified source IP address for outgoing packets.
USERCTL=answeranswer is one of the following:
yes — Non-root users are allowed to control this device.
no — Non-root users are not allowed to control this device.
bonding kernel module and a special network interface called a channel bonding interface. Channel bonding enables two or more network interfaces to act as one, simultaneously increasing the bandwidth and providing redundancy.
/etc/sysconfig/network-scripts/ directory called ifcfg-bondN, replacing N with the number for the interface, such as 0.
DEVICE directive must be bondN, replacing N with the number for the interface.
DEVICE=bond0
IPADDR=192.168.1.1
NETMASK=255.255.255.0
ONBOOT=yes
BOOTPROTO=none
USERCTL=no
BONDING_OPTS="bonding parameters separated by spaces"MASTER and SLAVE directives to their configuration files. The configuration files for each of the channel-bonded interfaces can be nearly identical.
DEVICE=ethN
BOOTPROTO=none
ONBOOT=yes
MASTER=bond0
SLAVE=yes
USERCTL=noN with the numerical value for the interface.
bonding.conf/etc/modprobe.d/ directory. Note that you can name this file anything you like as long as it ends with a .conf extension. Insert the following line in this new file:
alias bondN bondingN with the interface number, such as 0. For each configured channel bonding interface, there must be a corresponding entry in your new /etc/modprobe.d/bonding.conf file.
BONDING_OPTS="bonding parameters" directive in the ifcfg-bondN interface file. Do not specify options for the bonding device in /etc/modprobe.d/bonding.conf, or in the deprecated /etc/modprobe.conf file. For further instructions and advice on configuring the bonding module and to view the list of bonding parameters, refer to Section 24.7.2, “Using Channel Bonding”.
ifcfg-if-name:alias-value naming scheme.
ifcfg-eth0:0 file could be configured to specify DEVICE=eth0:0 and a static IP address of 10.0.0.2, serving as an alias of an Ethernet interface already configured to receive its IP information via DHCP in ifcfg-eth0. Under this configuration, eth0 is bound to a dynamic IP address, but the same physical network card can receive requests via the fixed, 10.0.0.2 IP address.
ifcfg-if-name-clone-name. While an alias file allows multiple addresses for an existing interface, a clone file is used to specify additional options for an interface. For example, a standard DHCP Ethernet interface called eth0, may look similar to this:
DEVICE=eth0 ONBOOT=yes BOOTPROTO=dhcp
USERCTL directive is no if it is not specified, users cannot bring this interface up and down. To give users the ability to control the interface, create a clone by copying ifcfg-eth0 to ifcfg-eth0-user and add the following line to ifcfg-eth0-user:
USERCTL=yes
/sbin/ifup eth0-user command because the configuration options from ifcfg-eth0 and ifcfg-eth0-user are combined. While this is a very basic example, this method can be used with a variety of options and interfaces.
ifcfg-pppXX is a unique number corresponding to a specific interface.
wvdial, the Network Administration Tool or Kppp is used to create a dialup account. It is also possible to create and edit this file manually.
ifcfg-ppp0 file:
DEVICE=ppp0 NAME=test WVDIALSECT=test MODEMPORT=/dev/modem LINESPEED=115200 PAPNAME=test USERCTL=true ONBOOT=no PERSIST=no DEFROUTE=yes PEERDNS=yes DEMAND=no IDLETIMEOUT=600
ifcfg-sl0.
DEFROUTE=answeranswer is one of the following:
yes — Set this interface as the default route.
no — Do not set this interface as the default route.
DEMAND=answeranswer is one of the following:
yes — This interface allows pppd to initiate a connection when someone attempts to use it.
no — A connection must be manually established for this interface.
IDLETIMEOUT=valuevalue is the number of seconds of idle activity before the interface disconnects itself.
INITSTRING=stringstring is the initialization string passed to the modem device. This option is primarily used in conjunction with SLIP interfaces.
LINESPEED=valuevalue is the baud rate of the device. Possible standard values include 57600, 38400, 19200, and 9600.
MODEMPORT=devicedevice is the name of the serial device that is used to establish the connection for the interface.
MTU=valuevalue is the Maximum Transfer Unit (MTU) setting for the interface. The MTU refers to the largest number of bytes of data a frame can carry, not counting its header information. In some dialup situations, setting this to a value of 576 results in fewer packets dropped and a slight improvement to the throughput for a connection.
NAME=namename is the reference to the title given to a collection of dialup connection configurations.
PAPNAME=namename is the username given during the Password Authentication Protocol (PAP) exchange that occurs to allow connections to a remote system.
PERSIST=answeranswer is one of the following:
yes — This interface should be kept active at all times, even if deactivated after a modem hang up.
no — This interface should not be kept active at all times.
REMIP=addressaddress is the IP address of the remote system. This is usually left unspecified.
WVDIALSECT=namename associates this interface with a dialer configuration in /etc/wvdial.conf. This file contains the phone number to be dialed and other important information for the interface.
ifcfg-lo/etc/sysconfig/network-scripts/ifcfg-lo, should never be edited manually. Doing so can prevent the system from operating correctly.
ifcfg-irlan0ifcfg-plip0/etc/sysconfig/network-scripts/ directory: /sbin/ifdown and /sbin/ifup.
ifup and ifdown interface scripts are symbolic links to scripts in the /sbin/ directory. When either of these scripts are called, they require the value of the interface to be specified, such as:
ifup eth0ifup and ifdown interface scripts are the only scripts that the user should use to bring up and take down network interfaces.
/etc/rc.d/init.d/functions and /etc/sysconfig/network-scripts/network-functions. Refer to Section 8.5, “Network Function Files” for more information.
/etc/sysconfig/network-scripts/ directory:
ifup-aliasesifup-ippp and ifdown-ipppifup-ipv6 and ifdown-ipv6ifup-plipifup-plusbifup-post and ifdown-postifup-ppp and ifdown-pppifup-routesifdown-sit and ifup-sitifup-wireless/etc/sysconfig/network-scripts/ directory can cause interface connections to act irregularly or fail. Only advanced users should modify scripts related to a network interface.
/sbin/service command on the network service (/etc/rc.d/init.d/network), as illustrated the following command:
/sbin/service network actionaction can be either start, stop, or restart.
/sbin/service network statusroute command to display the IP routing table.
/etc/sysconfig/network-scripts/route-interface file. For example, static routes for the eth0 interface would be stored in the /etc/sysconfig/network-scripts/route-eth0 file. The route-interface file has two formats: IP command arguments and network/netmask directives.
default viaX.X.X.Xdevinterface
X.X.X.X is the IP address of the default gateway. The interface is the interface that is connected to, or can reach, the default gateway.
X.X.X.X/XviaX.X.X.Xdevinterface
X.X.X.X/X is the network number and netmask for the static route. X.X.X.X and interface are the IP address and interface for the default gateway respectively. The X.X.X.X address does not have to be the default gateway IP address. In most cases, X.X.X.X will be an IP address in a different subnet, and interface will be the interface that is connected to, or can reach, that subnet. Add as many static routes as required.
route-eth0 file using the IP command arguments format. The default gateway is 192.168.0.1, interface eth0. The two static routes are for the 10.10.10.0/24 and 172.16.1.0/24 networks:
default via 192.168.0.1 dev eth0 10.10.10.0/24 via 192.168.0.1 dev eth0 172.16.1.0/24 via 192.168.0.1 dev eth0
10.10.10.0/24 via 10.10.10.1 dev eth1
ifup command: "RTNETLINK answers: File exists" or 'Error: either "to" is a duplicate, or "X.X.X.X" is a garbage.', where X.X.X.X is the gateway, or a different IP address. These errors can also occur if you have another route to another network using the default gateway. Both of these errors are safe to ignore.
route-interface files. The following is a template for the network/netmask format, with instructions following afterwards:
ADDRESS0=X.X.X.XNETMASK0=X.X.X.XGATEWAY0=X.X.X.X
ADDRESS0=X.X.X.X is the network number for the static route.
NETMASK0=X.X.X.X is the netmask for the network number defined with ADDRESS0=X.X.X.X.
GATEWAY0=X.X.X.X is the default gateway, or an IP address that can be used to reach ADDRESS0=X.X.X.X
route-eth0 file using the network/netmask directives format. The default gateway is 192.168.0.1, interface eth0. The two static routes are for the 10.10.10.0/24 and 172.16.1.0/24 networks. However, as mentioned before, this example is not necessary as the 10.10.10.0/24 and 172.16.1.0/24 networks would use the default gateway anyway:
ADDRESS0=10.10.10.0 NETMASK0=255.255.255.0 GATEWAY0=192.168.0.1 ADDRESS1=172.16.1.0 NETMASK1=255.255.255.0 GATEWAY1=192.168.0.1
ADDRESS0, ADDRESS1, ADDRESS2, and so on.
ADDRESS0=10.10.10.0 NETMASK0=255.255.255.0 GATEWAY0=10.10.10.1
/etc/sysconfig/network-scripts/network-functions file contains the most commonly used IPv4 functions, which are useful to many interface control scripts. These functions include contacting running programs that have requested information about changes in the status of an interface, setting hostnames, finding a gateway device, verifying whether or not a particular device is down, and adding a default route.
/etc/sysconfig/network-scripts/network-functions-ipv6 file exists specifically to hold this information. The functions in this file configure and delete static IPv6 routes, create and remove tunnels, add and remove IPv6 addresses to an interface, and test for the existence of an IPv6 address on an interface.
/usr/share/doc/initscripts-version/sysconfig.txt/usr/share/doc/iproute-version/ip-cref.psip command, which can be used to manipulate routing tables, among other things. Use the ggv or kghostview application to view this file.
Table of Contents
httpd if you are running a web server). However, if you do not need to provide a service, you should turn it off to minimize your exposure to possible bug exploits.
| Runlevel | Description |
|---|---|
0
| Used to halt the system. This runlevel is reserved and cannot be changed. |
1
| Used to run in a single-user mode. This runlevel is reserved and cannot be changed. |
2
| Not used by default. You are free to define it yourself. |
3
| Used to run in a full multi-user mode with a command line user interface. |
4
| Not used by default. You are free to define it yourself. |
5
| Used to run in a full multi-user mode with a graphical user interface. |
6
| Used to reboot the system. This runlevel is reserved and cannot be changed. |
~]$ runlevel
N 5runlevel command displays previous and current runlevel. In this case it is number 5, which means the system is running in a full multi-user mode with a graphical user interface.
/etc/inittab file, which contains a line near the end of the file similar to the following:
id:5:initdefault:
~]$ su -
Password:~]# nano /etc/inittabirqbalance service is enabled. In most cases, this service is installed and configured to run during the Red Hat Enterprise Linux 6 installation. To verify that irqbalance is running, as root, type the following at a shell prompt:
~]# service irqbalance status
irqbalance (pid 1234) is running...system-config-services at a shell prompt (e.g., xterm or GNOME Terminal).
/etc/rc.d/init.d/ directory, and the services controlled by xinetd) along with their description and the current status. See Table 9.2, “Possible service states” for a complete list of used icons and an explanation of their meaning.
| Icon | Description |
|---|---|
Green bullet
| The service is enabled. |
Red bullet
| The service is disabled. |
Control panel
| The service is enabled for selected runlevels only. |
Plugged plug
| The service is running. |
Unplugged plug
| The service is stopped. |
Exclamation mark
| There is something wrong with the service. |
Question mark
| The status of the service is unknown. |
~]$ su -
Password:~]# ntsysv
/etc/rc.d/init.d/ directory) along with their current status and a description obtainable by pressing F1. See Table 9.3, “Possible service states” for a list of used symbols and an explanation of their meaning.
| Symbol | Description |
|---|---|
| [*] | The service is enabled. |
| [ ] | The service is disabled. |
service command as described in Section 9.3.2, “Running the Service”.
service command as described in Section 9.3.3, “Stopping the Service”.
--level option followed by the string of numbers from 0 to 6 representing each runlevel you want to configure. For example, to configure runlevels 3 and 5, type:
~]# ntsysv --level 35~]$ su -
Password:/etc/rc.d/init.d/ directory, and the services controlled by xinetd), either type chkconfig --list, or use chkconfig with no additional arguments. You should be presented with an output similar to this:
~]# chkconfig --list
NetworkManager 0:off 1:off 2:on 3:on 4:on 5:on 6:off
abrtd 0:off 1:off 2:off 3:on 4:off 5:on 6:off
acpid 0:off 1:off 2:on 3:on 4:on 5:on 6:off
anamon 0:off 1:off 2:off 3:off 4:off 5:off 6:off
atd 0:off 1:off 2:off 3:on 4:on 5:on 6:off
auditd 0:off 1:off 2:on 3:on 4:on 5:on 6:off
avahi-daemon 0:off 1:off 2:off 3:on 4:on 5:on 6:off
... several lines omitted ...
wpa_supplicant 0:off 1:off 2:off 3:off 4:off 5:off 6:off
xinetd based services:
chargen-dgram: off
chargen-stream: off
cvs: off
daytime-dgram: off
daytime-stream: off
discard-dgram: off
... several lines omitted ...
time-stream: offchkconfig --list followed by the name of the service:
~]# chkconfig --list sshd
sshd 0:off 1:off 2:on 3:on 4:on 5:on 6:offchkconfig --list service to display the status of a service that is managed by xinetd. In that case, the output will simply contain the information whether the service is enabled or disabled:
~]# chkconfig --list rsync
rsync offchkconfig service on. For instance:
~]# chkconfig httpd on--level option followed by the string of numbers from 0 to 6 representing each runlevel in which you want the service to run. For example, to enable the abrtd for runlevels 3 and 5, type:
~]# chkconfig abrtd on --level 35service command as described in Section 9.3.2, “Running the Service”.
chkconfig service on only, as the --level option is not allowed:
~]# chkconfig rsync onchkconfig service off. For instance:
~]# chkconfig httpd off--level option followed by the string of numbers from 0 to 6 representing each runlevel in which you do not want the service to run. For example, to disable the abrtd for runlevels 2 and 4, type:
~]# chkconfig abrtd off --level 24service command as described in Section 9.3.3, “Stopping the Service”.
chkconfig service off only, as the --level option is not allowed:
~]# chkconfig rsync off/etc/init.d/ directory. To use it, make sure you have superuser privileges:
~]$ su -
Password:service service_name status. For example:
~]# service httpd status
httpd (pid 7474) is running...--status-all option:
~]# service --status-all
abrt (pid 1492) is running...
acpid (pid 1305) is running...
atd (pid 1540) is running...
auditd (pid 1103) is running...
automount (pid 1315) is running...
Avahi daemon is running
cpuspeed is stopped
... several lines omitted ...
wpa_supplicant (pid 1227) is running...service service_name start. For example:
~]# service httpd start
Starting httpd: [ OK ]service service_name stop. For example:
~]# service httpd stop
Stopping httpd: [ OK ]service service_name restart. For example:
~]# service httpd restart
Stopping httpd: [ OK ]
Starting httpd: [ OK ]man chkconfigchkconfig utility containing the full documentation on its usage.
man ntsysvntsysv utility containing the full documentation on its usage.
man serviceservice utility containing the full documentation on its usage.
man system-config-servicessystem-config-services utility containing the full documentation on its usage.
system-config-authentication command.
openldap-clients package must be installed in order to use an LDAP server for the user database.
ldaps).
ldaps://) URL or the TLS option to connect to the LDAP server.
portmap and ypbind services are started and enabled to start at boot time.
krb5-server package must be installed and Kerberos must be configured properly.
user mode.
winbindd service, refer to Section 17.1.2, “Samba Daemons and Related Services”.
krb5-libs and krb5-workstation packages.
kadmind process in the realm.
/etc/security/access.conf file to check for local user authorization rules.
authconfig command-line tool updates all of the configuration files and services required for system authentication, according to the settings passed to the script. Along with allowing all of the identity and authentication configuration options that can be set through the UI, the authconfig tool can also be used to create backup and kickstart files.
authconfig options, check the help output and the man page.
authconfig:
--update or --test option. One of those options is required for the command to run successfully. Using --update writes the configuration changes. --test prints the changes to stdout but does not apply the changes to the configuration.
--enableldap. To use LDAP as the authentication source, use --enableldapauth and then the requisite connection information, like the LDAP server name, base DN for the user suffix, and (optionally) whether to use TLS. The authconfig command also has options to enable or disable RFC 2307bis schema for user entries, which is not possible through the Authentication Configuration UI.
ldap or ldaps) and the port number. Do not use a secure LDAP URL (ldaps) with the --enableldaptls option.
authconfig --enableldap --enableldapauth --ldapserver=ldap://ldap.example.com:389,ldap://ldap2.example.com:389 --ldapbasedn="ou=people,dc=example,dc=com" --enableldaptls --ldaploadcacert=https://ca.server.example.com/caCert.crt --update
--ldapauth for LDAP password authentication, it is possible to use Kerberos with the LDAP user store. These options are described in Section 10.1.4.5, “Configuring Kerberos Authentication”.
--enablenis. This automatically uses NIS authentication, unless the Kerberos parameters are explicitly set, so it uses Kerberos authentication (Section 10.1.4.5, “Configuring Kerberos Authentication”). The only parameters are to identify the NIS server and NIS domain; if these are not used, then the authconfig service scans the network for NIS servers.
authconfig --enablenis --nisdomain EXAMPLE --nisserver nis.example.com --update
authconfig --enablewinbind --enablewinbindauth --smbsecurity user|server --enablewinbindoffline --smbservers=ad.example.com --smbworkgroup=EXAMPLE --update
authconfig --enablewinbind --enablewinbindauth --smbsecurity ads --enablewinbindoffline --smbservers=ad.example.com --smbworkgroup=EXAMPLE --smbrealm EXAMPLE.COM --winbindtemplateshell=/bin/sh --update
authconfig help.
authconfig NIS or LDAP options --enablekrb5 --krb5realm EXAMPLE --krb5kdc kdc.example.com:88,server.example.com:88 --krb5adminserver server.example.com:749 --enablekrb5kdcdns --enablekrb5realmdns --updateauthconfig --enablemkhomedir --update
authconfig --passalgo=sha512 --update
authconfig settings, like LDAP user stores.
authconfig --enablefingerprint --update
--enablesmartcard option:
authconfig --enablesmartcard --update
authconfig --enablesmartcard --smartcardaction=0 --update
--enablerequiresmartcard option until you have successfully authenticated to the system using a smart card. Otherwise, users may be unable to log into the system.
--update option updates all of the configuration files with the configuration changes. There are a couple of alternative options with slightly different behavior:
--kickstart writes the updated configuration to a kickstart file.
--test prints the full configuration, with changes, to stdout but does not edit any configuration files.
authconfig can be used to back up and restore previous configurations. All archives are saved to a unique subdirectory in the /var/lib/authconfig/ directory. For example, the --savebackup option gives the backup directory as 2011-07-01:
authconfig --savebackup=2011-07-01
/var/lib/authconfig/backup-2011-07-01 directory.
--restorebackup option. authconfig automatically makes a backup of the configuration before it applies any changes (with the --update option). The configuration can be restored from that automatic backup using the --restorelastbackup option.
/home and the system is configured to create home directories the first time users log in, then these directories are created with the wrong permissions.
/home directory to the home directory that is created on the local system. For example:
# semanage fcontext -a -e /home /home/locale
pam_oddjob_mkhomedir.so library, which the Authentication Configuration Tool uses to create home directories. The pam_oddjob_mkhomedir.so library, unlike the default pam_mkhomedir.so library, can create SELinux labels.
pam_oddjob_mkhomedir.so library if it is available. Otherwise, it will default to using pam_mkhomedir.so.
oddjobd service is running.
# semanage fcontext -a -e /home /home/locale # restorecon -R -v /home/locale
.conf file. The default file is /etc/sssd/sssd.conf, although alternative files can be passed to SSSD by using the --c option with the sssd command:
# sssd --c /etc/sssd/customfile.conf
[domain/LDAP]. The configuration file uses simple key = value lines to set the configuration. Comment lines are set by either a hash sign (#) or a semicolon (;)
[section] # Comment line key1 = val1 key10 = val1,val2
service command or the /etc/init.d/sssd script can start SSSD. For example:
# service start sssd.service
authconfig command:
# authconfig --enablesssd --update
sssd.conf file. on sections. The [sssd] section also lists the services that are active and should be started when sssd starts within the services directive.
sssd_nss module. This is configured in the [nss] section of the configuration.
sssd_pam PAM module. This is configured in the [pam] section of the configuration.
monitor, a special service that monitors and starts or restarts all other SSSD services. Its options are specified in the [sssd] section of the /etc/sssd/sssd.conf configuration file.
sssd_nss, which instructs the system to use SSSD to retrieve user information. The NSS configuration must include a reference to the SSSD module, and then the SSSD configuration sets how SSSD interacts with NSS.
sssd.conf file.
# vim /etc/sssd/sssd.conf
[sssd]
config_file_version = 2
reconnection_retries = 3
sbus_timeout = 30
services = nss, pam[nss] section, change any of the NSS parameters. These are listed in Table 10.1, “SSSD [nss] Configuration Parameters”.
[nss] filter_groups = root filter_users = root reconnection_retries = 3 entry_cache_timeout = 300 entry_cache_nowait_percentage = 75
service sssd restart
| Parameter | Value Format | Description |
|---|---|---|
| enum_cache_timeout | integer | Specifies how long, in seconds, sssd_nss should cache requests for information about all users (enumerations). |
| entry_cache_nowait_percentage | integer |
Specifies how long sssd_nss should return cached entries before refreshing the cache. Setting this to zero (0) disables the entry cache refresh.
This configures the entry cache to update entries in the background automatically if they are requested if the time before the next update is a certain percentage of the next interval. For example, if the interval is 300 seconds and the cache percentage is 75, then the entry cache will begin refreshing when a request comes in at 225 seconds — 75% of the interval.
The values for this option are 0 to 99, which sets the percentage based on the
entry_cache_timeout value.
|
| entry_negative_timeout | integer | Specifies how long, in seconds, sssd_nss should cache negative cache hits. A negative cache hit is a query for an invalid database entries, including non-existent entries. |
| filter_users, filter_groups | string |
Tells SSSD to exclude certain users from being fetched from the NSS database. This is particularly useful for system accounts such as root.
|
| filter_users_in_groups | Boolean |
Sets whether users listed in the filter_users list appear in group memberships when performing group lookups. If set to FALSE, group lookups return all users that are members of that group. If not specified, this value defaults to TRUE, which filters the group member lists.
|
sssd_pam, which instructs the system to use SSSD to retrieve user information. The PAM configuration must include a reference to the SSSD module, and then the SSSD configuration sets how SSSD interacts with PAM.
authconfig to enable SSSD for system authentication.
# authconfig --update --enablesssd --enablesssdauthThis automatically updates the PAM configuration to reference all of the SSSD modules:
#%PAM-1.0 # This file is auto-generated. # User changes will be destroyed the next time authconfig is run. auth required pam_env.so auth sufficient pam_unix.so nullok try_first_pass auth requisite pam_succeed_if.so uid >= 500 quietauth sufficient pam_sss.so use_first_passauth required pam_deny.so account required pam_unix.so account sufficient pam_localuser.so account sufficient pam_succeed_if.so uid < 500 quietaccount [default=bad success=ok user_unknown=ignore] pam_sss.soaccount required pam_permit.so password requisite pam_cracklib.so try_first_pass retry=3 password sufficient pam_unix.so sha512 shadow nullok try_first_pass use_authtokpassword sufficient pam_sss.so use_authtokpassword required pam_deny.so session optional pam_keyinit.so revoke session required pam_limits.so session [success=1 default=ignore] pam_succeed_if.so service in crond quiet use_uidsession sufficient pam_sss.sosession required pam_unix.so
include statements, as necessary.
sssd.conf file.
# vim /etc/sssd/sssd.conf
[sssd]
config_file_version = 2
reconnection_retries = 3
sbus_timeout = 30
services = nss, pam[pam] section, change any of the PAM parameters. These are listed in Table 10.2, “SSSD [pam] Configuration Parameters”.
[pam] reconnection_retries = 3 offline_credentials_expiration = 2 offline_failed_login_attempts = 3 offline_failed_login_delay = 5
service sssd restart
| Parameter | Value Format | Description |
|---|---|---|
| offline_credentials_expiration | integer |
Sets how long, in days, to allow cached logins if the authentication provider is offline. This value is measured from the last successful online login. If not specified, this defaults to zero (0), which is unlimited.
|
| offline_failed_login_attempts | integer |
Sets how many failed login attempts are allowed if the authentication provider is offline. If not specified, this defaults to zero (0), which is unlimited.
|
| offline_failed_login_delay | integer |
Sets how long to prevent login attempts if a user hits the failed login attempt limit. If set to zero (0), the user cannot authenticate while the provider is offline once he hits the failed attempt limit. Only a successful online authentication can re-enable offline authentication. If not specified, this defaults to five (5).
|
jsmith in the ldap.example.com domain and jsmith in the ldap.otherexample.com domain. SSSD allows requests using fully-qualified domain names, so requesting information for jsmith@ldap.example.com returns the the proper user account. Specifying only the username returns the user for whichever domain comes first in the lookup order.
filter_users option, which excludes the specified users from being returned in a search.
| Identification Provider | Authentication Provider |
|---|---|
| LDAP | LDAP |
| LDAP | Kerberos |
| proxy | LDAP |
| proxy | Kerberos |
| proxy | proxy |
domains = LOCAL,Name[domain/Name] id_provider =typeauth_provider =typeprovider_specific = valueglobal = value
| Parameter | Value Format | Description |
|---|---|---|
| id_provider | string |
Specifies the data provider identity backend to use for this domain. The supported identity backends are:
|
| auth_provider | string |
Sets the authentication provider used for the domain. The default value for this option is the value of id_provider. The supported authentication providers are ldap, krb5 (Kerberos), proxy, and none.
|
| min_id,max_id | integer |
Optional. Specifies the UID and GID range for the domain. If a domain contains entries that are outside that range, they are ignored. The default value for min_id is 1; the default value for max_id is 0, which is unlimited.
Important
The default min_id value is the same for all types of identity provider. If LDAP directories are using UID numbers that start at one, it could cause conflicts with users in the local /etc/passwd file. To avoid these conflicts, set min_id to 1000 or higher as possible.
|
| enumerate | Boolean |
Optional. Specifies whether to list the users and groups of a domain. Enumeration means that the entire set of available users and groups on the remote source is cached on the local machine. When enumeration is disabled, users and groups are only cached as they are requested.
Warning
When enumeration is enabled, reinitializing a client results in a complete refresh of the entire set of available users and groups from the remote source. Similarly, when SSSD is connected to a new server, the entire set of available users and groups from the remote source is pulled and cached on the local machine. In a domain with a large number of clients connected to a remote source, this refresh process can harm the network performance because of frequent queries from the clients. If the set of available users and groups is large enough, it degrades client performance as well.
false, which disables enumeration.
|
| timeout | integer |
Optional. Specifies the timeout in seconds for the domain. The default value is ten seconds. The timeout setting checks that the provider is available for requests and is useful for networks with long lag times or that are geographically dispersed.
If the timeout value is zero (0), SSSD reverts to the default value. A timeout value of zero cannot be enforced because this forces SSSD into a loop.
|
| cache_credentials | Boolean |
Optional. Specifies whether to store user credentials in the local SSSD domain database cache. The default value for this parameter is false. Set this value to true for domains other than the LOCAL domain to enable offline authentication.
|
| entry_cache_timeout | integer | Optional. Specifies how long, in seconds, SSSD should cache positive cache hits. A positive cache hit is a successful query. |
| use_fully_qualified_names | Boolean |
Optional. Specifies whether requests to this domain require fully-qualified domain names. If set to true, all requests to this domain must use fully-qualified domain names. It also means that the output from the request displays the fully-qualified name. Restricting requests to fully-qualified user names allows SSSD to differentiate between domains with users with conflicting usernames.
If
use_fully_qualified_names is set to false, it is possible to use the fully-qualified name in the requests, but only the simplified version is displayed in the output.
SSSD can only parse names based on the domain name, not the realm name. The same name can be used for both domains and realms, however.
|
sssd-ldap(5).
| Parameter | Description | Required or Optional |
|---|---|---|
| ldap_uri | Gives a comma-separated list of the URIs of the LDAP servers to which SSSD will connect. The list is given in order of preference, so the first server in the list is tried first. Listing additional servers provides failover protection. | Required |
| ldap_search_base | Gives the base DN to use for performing LDAP user operations. | Required |
| ldap_tls_reqcert |
Specifies how to check for SSL server certificates in a TLS session. There are four options:
| Required (unless LDAPS is used) |
| ldap_tls_cacert | Gives the full path and file name to the file that contains the CA certificates for all of the CAs that SSSD recognizes. SSSD will accept any certificate issued by these CAs. | Required (unless LDAPS is used) |
| ldap_referrals |
Sets whether SSSD will use LDAP referrals, meaning forwarding queries from one LDAP database to another. SSSD supports database-level and subtree referrals. For referrals within the same LDAP server, SSSD will adjust the DN of the entry being queried. For referrals that go to different LDAP servers, SSSD does an exact match on the DN. Setting this value to true enables referrals; by default, referrals are disabled.
| Optional |
| ldap_schema |
Sets what version of schema to use when searching for user entries. This can be either rfc2307 or rfc2307bis. The default is rfc2307.
In RFC 2307, group objects use a multi-valued attribute,
memberuid, which lists the names of the users that belong to that group. In RFC 2307bis, group objects use the member attribute, which contains the full distinguished name (DN) of the user entry. Since this enables more accurate member locations, RFC 2307bis allows nested groups. Because these different schema use different definitions for group membership, using the wrong LDAP schema with SSSD can affect both viewing and managing network resources, even if the appropriate permissions are in place.
For example, with RFC 2307bis, all groups are returned when using nested groups or primary/secondary groups.
$ id uid=500(myserver) gid=500(myserver) groups=500(myserver),510(myothergroup)
If SSSD is using RFC 2307 schema, only the primary group is returned.
This setting only affects how SSSD determines the group members. It does not change the actual user data.
| Optional |
| ldap_search_timeout |
Sets the time, in seconds, that LDAP searches are allowed to run before they are canceled and cached results are returned. This defaults to five when the enumerate value is false and defaults to 30 when enumerate is true.
When an LDAP search times out, SSSD automatically switches to offline mode.
| Optional |
| ldap_network_timeout | Sets the time, in seconds, SSSD attempts to poll an LDAP server after a connection attempt fails. The default is six seconds. | Optional |
| ldap_opt_timeout | Sets the time, in seconds, to wait before aborting synchronous LDAP operations if no response is received from the server. This option also controls the timeout when communicating with the KDC in case of a SASL bind. The default is five seconds. | Optional |
sssd.conf file. For example:
domains = LOCAL,LDAP1,AD,PROXYNIS
ldap_uri option:
# A native LDAP domain [domain/LDAP] enumerate = false cache_credentials = TRUE id_provider = ldap auth_provider = ldap ldap_uri = ldaps://ldap.example.com:636 ldap_search_base = dc=example,dc=com
ldap_tls_reqcert option to use Start TLS and then ldap_tls_cacert to identify the CA certificate which issued the SSL server certificates.
# A native LDAP domain [domain/LDAP] enumerate = false cache_credentials = TRUE id_provider = ldap auth_provider = ldap ldap_uri = ldap://ldap.example.com ldap_search_base = dc=example,dc=com ldap_tls_reqcert = demand ldap_tls_cacert = /etc/pki/tls/certs/ca-bundle.crt
c_rehash function to create the appropriate symlinks.
sssd-ldap(5).
# Example LDAP domain where the LDAP server is an Active Directory 2003 server. [domain/AD] description = LDAP domain with AD server enumerate = false min_id = 1000 ; id_provider = ldap auth_provider = ldap ldap_uri = ldap://your.ad.server.com ldap_schema = rfc2307bis ldap_search_base = dc=example,dc=com ldap_default_bind_dn = cn=Administrator,cn=Users,dc=example,dc=com ldap_default_authtok_type = password ldap_default_authtok = secret ldap_user_object_class = person ldap_user_name = msSFU30Name ldap_user_uid_number = msSFU30UidNumber ldap_user_gid_number = msSFU30GidNumber ldap_user_home_directory = msSFU30HomeDirectory ldap_user_shell = msSFU30LoginShell ldap_user_principal = userPrincipalName ldap_group_object_class = group ldap_group_name = msSFU30Name ldap_group_gid_number = msSFU30GidNumber
sssd-ldap(5).
# Example LDAP domain where the LDAP server is an Active Directory 2003 R2 or an Active Directory 2008 server. [domain/AD] description = LDAP domain with AD server ; debug_level = 9 enumerate = false id_provider = ldap auth_provider = ldap chpass_provider = ldap ldap_uri = ldap://your.ad.server.com ldap_tls_cacertdir = /etc/openldap/cacerts ldap_tls_cacert = /etc/openldap/cacerts/test.cer ldap_search_base = dc=example,dc=com ldap_default_bind_dn = cn=Administrator,cn=Users,dc=example,dc=com ldap_default_authtok_type = password ldap_default_authtok = secret ldap_pwd_policy = none ldap_user_object_class = user ldap_group_object_class = group
ldap_uri option instead of the server name may cause the TLS/SSL connection to fail. TLS/SSL certificates contain the server name, not the IP address. However, the subject alternative name field in the certificate can be used to include the IP address of the server, which allows a successful secure connection using an IP address.
-signkey) is the key of the issuer of whatever CA originally issued the certificate. If this is done by an external CA, it requires a separate PEM file; if the certificate is self-signed, then this is the certificate itself. For example:
openssl x509 -x509toreq -in old_cert.pem -out req.pem -signkey key.pem
openssl x509 -x509toreq -in old_cert.pem -out req.pem -signkey old_cert.pem
/etc/pki/tls/openssl.cnf configuration file to include the server's IP address under the [ v3_ca ] section:
subjectAltName = IP:10.0.0.10
openssl x509 -req -in req.pem -out new_cert.pem -extfile ./openssl.cnf -extensions v3_ca -signkey old_cert.pem
-extensions option sets which extensions to use with the certificate. For this, it should be v3_ca to load the appropriate section.
old_cert.pem file into the new_cert.pem file to keep all relevant information in one file.
krb5_kpasswd option to specify where the password changing service is running or if it is running on a non-default port. If the krb5_kpasswd option is not defined, SSSD tries to use the Kerberos KDC to change the password.
# A domain with identities provided by LDAP and authentication by Kerberos [domain/KRBDOMAIN] enumerate = false id_provider = ldap chpass_provider = krb5 ldap_uri = ldap://ldap.example.com ldap_search_base = dc=example,dc=com ldap-tls_reqcert = demand ldap_tls_cacert = /etc/pki/tls/certs/ca-bundle.crt auth_provider = krb5 krb5_server = 192.168.1.1 krb5_realm = EXAMPLE.COM krb5_kpasswd = kadmin/changepw krb5_auth_timeout = 15
| Parameter | Description |
|---|---|
| chpass_provider | Specifies which service to use for password change operations. This is assumed to be the same as the authentication provider. To use Kerberos, set this to krb5. |
| krb5_server |
Gives a comma-separated list of IP addresses or hostnames of Kerberos servers to which SSSD will connect. The list is given in order of preference, so the first server in the list is tried first. Listing additional servers provides failover protection.
When using service discovery for KDC or kpasswd servers, SSSD first searches for DNS entries that specify UDP as the connection protocol, and then falls back to TCP.
|
| krb5_realm | Gives the Kerberos realm to use for SASL/GSS-API authentication. |
| krb5_lifetime | Requests a Kerberos ticket with the specified lifetime in seconds (s), minutes (m), hours (h) or days (d). |
| krb5_renewable_lifetime | Requests a renewable Kerberos ticket with a total lifetime that is specified in seconds (s), minutes (m), hours (h) or days (d). |
| krb5_renew_interval | Sets the time, in seconds, for SSSD to check if tickets should be renewed. Tickets are renewed automatically once they exceed half their lifetime. If this option is missing or set to zero, then automatic ticket renewal is disabled. |
| krb5_store_password_if_offline |
Sets whether to store user passwords if the Kerberos authentication provider is offline, and then to use that cache to request tickets when the provider is back online. The default is false, which does not store passwords.
|
| krb5_kpasswd | Lists alternate Kerberos kadmin servers to use if the change password service is not running on the KDC. |
| krb5_ccname_template |
Gives the directory to use to store the user's credential cache. This can be templatized, and the following tokens are supported:
krb5_ccname_template = FILE:%d/krb5cc_%U_XXXXXX |
| krb5_ccachedir |
Specifies the directory to store credential caches. This can be templatized, using the same tokens as krb5_ccname_template, except for %d and %P. If %u, %U, %p, or %h are used, then SSSD creates a private directory for each user; otherwise, it creates a public directory.
|
| krb5_auth_timeout | Gives the time, in seconds, before an online authentication or change password request is aborted. If possible, the authentication request is continued offline. The default is 15 seconds. |
| Parameter | Description |
|---|---|
| proxy_pam_target |
Specifies the target to which PAM must proxy as an authentication provider.. The PAM target is a file containing PAM stack information in the default PAM directory, /etc/pam.d/.
This is used to proxy an authentication provider.
Important
Ensure that the proxy PAM stack does not recursively include pam_sss.so.
|
| proxy_lib_name |
Specifies which existing NSS library to proxy identity requests through.
This is used to proxy an identity provider.
|
proxy_lib_name parameter. This library can be anything as long as it is compatible with the given authentication service. For a Kerberos authentication provider, it must be a Kerberos-compatible library, like NIS.
[domain/PROXY_KRB5] auth_provider = krb5 krb5_server = 192.168.1.1 krb5_realm = EXAMPLE.COM id_provider = proxy proxy_lib_name = nis enumerate = true cache_credentials = true
proxy_pam_target parameter. This library must be a PAM module that is compatible with the given identity provider. For example, this uses a PAM module with LDAP:
[domain/LDAP_PROXY] id_provider = ldap ldap_uri = ldap://example.com ldap_search_base = dc=example,dc=com auth_provider = proxy proxy_pam_target = sssdpamproxy enumerate = true cache_credentials = true
sssdpamproxy, so create a /etc/pam.d/sssdpamproxy file and load the PAM/LDAP modules:
auth required pam_ldap.so account required pam_ldap.so password required pam_ldap.so session required pam_ldap.so
proxy_pam_target for the authentication PAM module and proxy_lib_name for the service, like NIS or LDAP.
[domain/PROXY_PROXY] auth_provider = proxy id_provider = proxy proxy_lib_name = ldap proxy_pam_target = sssdproxyldap enumerate = true cache_credentials = true
/etc/pam.d/sssdproxyldap file which requires the pam_ldap.so module:
auth required pam_ldap.so account required pam_ldap.so password required pam_ldap.so session required pam_ldap.so
/etc/nslcd.conf file, the configuration file for the LDAP name service daemon, to contain the information for the LDAP directory:
uid nslcd gid ldap uri ldaps://ldap.example.com:636 base dc=example,dc=com ssl on tls_cacertdir /etc/openldap/cacerts
simple_allow_users and simple_allow_groups, which grant access explicitly to specific users (either the given users or group members) and deny access to everyone else. It is also possible to create deny lists (which deny access only to explicit people and implicitly allow everyone else access).
simple_allow_users|groups is set, only users from this list are allowed access. This setting supersedes the simple_deny_users list.
simple_allow_users|groups list is empty, users are allowed access unless they appear in the simple_deny_users list.
simple_allow_users|groups and simple_deny_users|groups is a configuration error. If this occurs, SSSD will output an error to the /var/log/sssd/sssd_default.log log file when loading the backend, but continue to start normally.
[domain/example.com] access_provider = simple simple_allow_users = jsmith,bjensen simple_allow_groups = itgroup
simple as an access provider.
ldap_access_filter) specifies which users are granted access to the specified host. The user filter must be used or all users are denied access.
[domain/example.com] access_provider = ldap ldap_access_filter = memberOf=cn=allowedusers,ou=Groups,dc=example,dc=com
/etc/sssd/sssd.conf file. The servers are listed in order of preference. This list can contain any number of servers.
ldap_uri = ldap://ldap0.example.com, ldap://ldap1.example.com, ldap://ldap2.example.com
ldap://ldap0.example.com, is the primary server. If this server fails, SSSD first attempts to connect to ldap1.example.com and then ldap2.example.com.
_service._protocol._domain TTL priority weight port hostname
/var/lib/sss/db/ directory.
exampleldap, the cache file is named cache_exampleldap.ldb.
resolv.conf file. This file is typically only read once, and so any changes made to this file are not automatically applied. This can cause NFS locking to fail on the machine where the NSCD service is running, unless that service is manually restarted.
/etc/nscd.conf file and rely on the SSSD cache for the passwd, group, and netgroup entries.
/etc/nscd.conf file:
enable-cache hosts yes enable-cache passwd no enable-cache group no enable-cache netgroup no
/var/log/sssd/ directory. SSSD produces a log file for each domain, as well as an sssd_pam.log and an sssd_nss.log file.
/var/log/secure file logs authentication failures and the reason for the failure.
# sssd --debug-level=9 --debug-timestamps=1
# sssd -d4 [sssd] [ldb] (3): server_sort:Unable to register control with rootdse! [sssd] [confdb_get_domains] (0): No domains configured, fatal error! [sssd] [get_monitor_config] (0): No domains configured.
/etc/sssd/sssd.conf file and create at least one domain.
[sssd] [get_monitor_config] (0): No services configured!
/etc/sssd/sssd.conf file and configure at least one service provider.
services entry in the /etc/sssd/sssd.conf file. If services are listed in multiple entries, only the last entry is recognized by SSSD.
# systemctl is-active sssd.service sssd (pid 21762) is running...
[nss] section of the /etc/sssd/sssd.conf file. Especially check the filter_users and filter_groups attributes.
/etc/nsswitch.conf file.
use_fully_qualified_domains attribute to TRUE in the /etc/sssd/sssd.conf file. This differentiates between different users in different domains with the same name.
[root@clientF11 tmp]# passwd user1000 Changing password for user user1000. New password: Retype new password: New Password: Reenter new Password: passwd: all authentication tokens updated successfully.
use_authtok option is correctly configured in your /etc/pam.d/system-auth file.
SSH (Secure Shell) is a protocol which facilitates secure communications between two systems using a client/server architecture and allows users to log into server host systems remotely. Unlike other remote communication protocols, such as FTP or Telnet, SSH encrypts the login session, rendering the connection difficult for intruders to collect unencrypted passwords.
telnet or rsh. A related program called scp replaces older programs designed to copy files between hosts, such as rcp. Because these older applications do not encrypt passwords transmitted between the client and the server, avoid them whenever possible. Using secure methods to log into remote systems decreases the risks for both the client system and the remote host.
openssh) as well as the OpenSSH server (openssh-server) and client (openssh-clients) packages. Note, the OpenSSH packages require the OpenSSL package (openssl) which installs several important cryptographic libraries, enabling OpenSSH to provide encrypted communications.
~]$ su -
Password:ssh, scp, and sftp), and those for the server (the sshd daemon).
/etc/ssh/ directory. See Table 11.1, “System-wide configuration files” for a description of its content.
| Configuration File | Description |
|---|---|
/etc/ssh/moduli
| Contains Diffie-Hellman groups used for the Diffie-Hellman key exchange which is critical for constructing a secure transport layer. When keys are exchanged at the beginning of an SSH session, a shared, secret value is created which cannot be determined by either party alone. This value is then used to provide host authentication. |
/etc/ssh/ssh_config
|
The default SSH client configuration file. Note that it is overridden by ~/.ssh/config if it exists.
|
/etc/ssh/sshd_config
|
The configuration file for the sshd daemon.
|
/etc/ssh/ssh_host_dsa_key
|
The DSA private key used by the sshd daemon.
|
/etc/ssh/ssh_host_dsa_key.pub
|
The DSA public key used by the sshd daemon.
|
/etc/ssh/ssh_host_key
|
The RSA private key used by the sshd daemon for version 1 of the SSH protocol.
|
/etc/ssh/ssh_host_key.pub
|
The RSA public key used by the sshd daemon for version 1 of the SSH protocol.
|
/etc/ssh/ssh_host_rsa_key
|
The RSA private key used by the sshd daemon for version 2 of the SSH protocol.
|
/etc/ssh/ssh_host_rsa_key.pub
|
The RSA public key used by the sshd for version 2 of the SSH protocol.
|
~/.ssh/ directory. See Table 11.2, “User-specific configuration files” for a description of its content.
| Configuration File | Description |
|---|---|
~/.ssh/authorized_keys
| Holds a list of authorized public keys for servers. When the client connects to a server, the server authenticates the client by checking its signed public key stored within this file. |
~/.ssh/id_dsa
| Contains the DSA private key of the user. |
~/.ssh/id_dsa.pub
| The DSA public key of the user. |
~/.ssh/id_rsa
|
The RSA private key used by ssh for version 2 of the SSH protocol.
|
~/.ssh/id_rsa.pub
|
The RSA public key used by ssh for version 2 of the SSH protocol
|
~/.ssh/identity
|
The RSA private key used by ssh for version 1 of the SSH protocol.
|
~/.ssh/identity.pub
|
The RSA public key used by ssh for version 1 of the SSH protocol.
|
~/.ssh/known_hosts
| Contains DSA host keys of SSH servers accessed by the user. This file is very important for ensuring that the SSH client is connecting the correct SSH server. |
ssh_config and sshd_config man pages for information concerning the various directives available in the SSH configuration files.
sshd daemon, type the following at a shell prompt:
~]# service sshd startsshd daemon, use the following command:
~]# service sshd stop~]# chkconfig sshd on@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @ @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY! Someone could be eavesdropping on you right now (man-in-the-middle attack)! It is also possible that the RSA host key has just been changed.
/etc/ssh/ directory (see Table 11.1, “System-wide configuration files” for a complete list), and restore them whenever you reinstall the system.
telnet, rsh, rlogin, and vsftpd.
~]#chkconfig telnet off~]#chkconfig rsh off~]#chkconfig rlogin off~]#chkconfig vsftpd off
/etc/ssh/sshd_config configuration file in a text editor such as vi or nano, and change the PasswordAuthentication option as follows:
PasswordAuthentication no
ssh, scp, or sftp to connect to the server from a client machine, generate an authorization key pair by following the steps below. Note that keys must be generated for each user separately.
~/.ssh/ directory. After reinstalling, copy it back to your home directory. This process can be done for all users on your system, including root.
~]$ ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/john/.ssh/id_rsa):~/.ssh/id_rsa) for the newly created key.
Your identification has been saved in /home/john/.ssh/id_rsa. Your public key has been saved in /home/john/.ssh/id_rsa.pub. The key fingerprint is: e7:97:c7:e2:0e:f9:0e:fc:c4:d7:cb:e5:31:11:92:14 john@penguin.example.com The key's randomart image is: +--[ RSA 2048]----+ | E. | | . . | | o . | | . .| | S . . | | + o o ..| | * * +oo| | O +..=| | o* o.| +-----------------+
~/.ssh/ directory:
~]$ chmod 755 ~/.ssh~/.ssh/id_rsa.pub into the ~/.ssh/authorized_keys on the machine to which you want to connect, appending it to its end if the file already exists.
~/.ssh/authorized_keys file using the following command:
~]$ chmod 644 ~/.ssh/authorized_keys~]$ ssh-keygen -t dsa
Generating public/private dsa key pair.
Enter file in which to save the key (/home/john/.ssh/id_dsa):~/.ssh/id_dsa) for the newly created key.
Your identification has been saved in /home/john/.ssh/id_dsa. Your public key has been saved in /home/john/.ssh/id_dsa.pub. The key fingerprint is: 81:a1:91:a8:9f:e8:c5:66:0d:54:f5:90:cc:bc:cc:27 john@penguin.example.com The key's randomart image is: +--[ DSA 1024]----+ | .oo*o. | | ...o Bo | | .. . + o. | |. . E o | | o..o S | |. o= . | |. + | | . | | | +-----------------+
~/.ssh/ directory:
~]$ chmod 775 ~/.ssh~/.ssh/id_dsa.pub into the ~/.ssh/authorized_keys on the machine to which you want to connect, appending it to its end if the file already exists.
~/.ssh/authorized_keys file using the following command:
~]$ chmod 644 ~/.ssh/authorized_keys~]$ ssh-keygen -t rsa1
Generating public/private rsa1 key pair.
Enter file in which to save the key (/home/john/.ssh/identity):~/.ssh/identity) for the newly created key.
Your identification has been saved in /home/john/.ssh/identity. Your public key has been saved in /home/john/.ssh/identity.pub. The key fingerprint is: cb:f6:d5:cb:6e:5f:2b:28:ac:17:0c:e4:62:e4:6f:59 john@penguin.example.com The key's randomart image is: +--[RSA1 2048]----+ | | | . . | | o o | | + o E | | . o S | | = + . | | . = . o . .| | . = o o..o| | .o o o=o.| +-----------------+
~/.ssh/ directory:
~]$ chmod 755 ~/.ssh~/.ssh/identity.pub into the ~/.ssh/authorized_keys on the machine to which you want to connect, appending it to its end if the file already exists.
~/.ssh/authorized_keys file using the following command:
~]$ chmod 644 ~/.ssh/authorized_keysssh-agent authentication agent. If you are running GNOME, you can configure it to prompt you for your passphrase whenever you log in and remember it during the whole session. Otherwise you can store the passphrase for a certain shell prompt.
/usr/bin/ssh-add in the Command field.
ssh, scp, or sftp.
~]$ ssh-add
Enter passphrase for /home/john/.ssh/id_rsa:ssh allows you to log in to a remote machine and execute commands there. It is a secure replacement for the rlogin, rsh, and telnet programs.
telnet, to log in to a remote machine named penguin.example.com, type the following command at a shell prompt:
~]$ ssh penguin.example.comssh username@hostname form. For example, to log in as john, type:
~]$ ssh john@penguin.example.comThe authenticity of host 'penguin.example.com' can't be established. RSA key fingerprint is 94:68:3a:3a:bc:f3:9a:9b:01:5d:b3:07:38:e2:11:0c. Are you sure you want to continue connecting (yes/no)?
yes to confirm. You will see a notice that the server has been added to the list of known hosts, and a prompt asking for your password:
Warning: Permanently added 'penguin.example.com' (RSA) to the list of known hosts. john@penguin.example.com's password:
~/.ssh/known_hosts file. To do so, open the file in a text editor, and remove a line containing the remote machine name at the beginning. Before doing this, however, contact the system administrator of the SSH server to verify the server is not compromised.
ssh program can be used to execute a command on the remote machine without logging in to a shell prompt. The syntax for that is ssh [username@]hostname command. For example, if you want to execute the whoami command on penguin.example.com, type:
~]$ ssh john@penguin.example.com whoami
john@penguin.example.com's password:
johnscp Utilityscp can be used to transfer files between machines over a secure, encrypted connection. In its design, it is very similar to rcp.
scp localfile username@hostname:remotefiletaglist.vim to a remote machine named penguin.example.com, type the following at a shell prompt:
~]$ scp taglist.vim john@penguin.example.com:.vim/plugin/taglist.vim
john@penguin.example.com's password:
taglist.vim 100% 144KB 144.5KB/s 00:00.vim/plugin/ to the same directory on the remote machine penguin.example.com, type the following command:
~]$ scp .vim/plugin/* john@penguin.example.com:.vim/plugin/
john@penguin.example.com's password:
closetag.vim 100% 13KB 12.6KB/s 00:00
snippetsEmu.vim 100% 33KB 33.1KB/s 00:00
taglist.vim 100% 144KB 144.5KB/s 00:00scp username@hostname:remotefile localfile.vimrc configuration file from the remote machine, type:
~]$ scp john@penguin.example.com:.vimrc .vimrc
john@penguin.example.com's password:
.vimrc 100% 2233 2.2KB/s 00:00sftp Utilitysftp utility can be used to open a secure, interactive FTP session. In its design, it is similar to ftp except that it uses a secure, encrypted connection.
sftp username@hostnamepenguin.example.com with john as a username, type:
~]$ sftp john@penguin.example.com
john@penguin.example.com's password:
Connected to penguin.example.com.
sftp>sftp utility accepts a set of commands similar to those used by ftp (see Table 11.3, “A selection of available sftp commands”).
| Command | Description |
|---|---|
ls [directory]
|
List the content of a remote directory. If none is supplied, a current working directory is used by default.
|
cd directory
|
Change the remote working directory to directory.
|
mkdir directory
|
Create a remote directory.
|
rmdir path
|
Remove a remote directory.
|
put localfile [remotefile]
|
Transfer localfile to a remote machine.
|
get remotefile [localfile]
|
Transfer remotefile from a remote machine.
|
sftp man page.
ssh -Y username@hostnamepenguin.example.com with john as a username, type:
~]$ ssh -Y john@penguin.example.com
john@penguin.example.com's password:~]$ system-config-printer &TCP/IP protocols via port forwarding. When using this technique, the SSH server becomes an encrypted conduit to the SSH client.
localhost, use a command in the following form:
ssh -L local-port:remote-hostname:remote-port username@hostnamemail.example.com using POP3 through an encrypted connection, use the following command:
~]$ ssh -L 1100:mail.example.com:110 mail.example.com1100 on the localhost to check for new email. Any requests sent to port 1100 on the client system will be directed securely to the mail.example.com server.
mail.example.com is not running an SSH server, but another machine on the same network is, SSH can still be used to secure part of the connection. However, a slightly different command is necessary:
~]$ ssh -L 1100:mail.example.com:110 other.example.com1100 on the client machine are forwarded through the SSH connection on port 22 to the SSH server, other.example.com. Then, other.example.com connects to port 110 on mail.example.com to check for new email. Note that when using this technique, only the connection between the client system and other.example.com SSH server is secure.
No parameter for the AllowTcpForwarding line in /etc/ssh/sshd_config and restarting the sshd service.
man sshman scpman sftpman sshdman ssh-keygenman ssh_configman sshd_configTable of Contents
smb.conf Filedhcp package contains an ISC DHCP server. First, install the package as the superuser:
~]# yum install dhcpdhcp package creates a file, /etc/dhcp/dhcpd.conf, which is merely an empty configuration file:
~]# cat /etc/dhcp/dhcpd.conf
#
# DHCP Server Configuration file.
# see /usr/share/doc/dhcp*/dhcpd.conf.sample/usr/share/doc/dhcp-<version>/dhcpd.conf.sample. You should use this file to help you configure /etc/dhcp/dhcpd.conf, which is explained in detail below.
/var/lib/dhcpd/dhcpd.leases to store the client lease database. Refer to Section 12.2.2, “Lease Database” for more information.
service dhcpd restart.
omshell command provides an interactive way to connect to, query, and change the configuration of a DHCP server. By using omshell, all changes can be made while the server is running. For more information on omshell, refer to the omshell man page.
routers, subnet-mask, domain-search, domain-name-servers, and time-offset options are used for any host statements declared below it.
subnet can be declared, a subnet declaration must be included for every subnet in the network. If it is not, the DHCP server fails to start.
range declared. Clients are assigned an IP address within the range.
subnet 192.168.1.0 netmask 255.255.255.0 {
option routers 192.168.1.254;
option subnet-mask 255.255.255.0;
option domain-search "example.com";
option domain-name-servers 192.168.1.1;
option time-offset -18000; # Eastern Standard Time
range 192.168.1.10 192.168.1.100;
}
range 192.168.1.10 and 192.168.1.100 to client systems.
default-lease-time 600;
max-lease-time 7200;
option subnet-mask 255.255.255.0;
option broadcast-address 192.168.1.255;
option routers 192.168.1.254;
option domain-name-servers 192.168.1.1, 192.168.1.2;
option domain-search "example.com";
subnet 192.168.1.0 netmask 255.255.255.0 {
range 192.168.1.10 192.168.1.100;
}
hardware ethernet parameter within a host declaration. As demonstrated in Example 12.3, “Static IP address using DHCP”, the host apex declaration specifies that the network interface card with the MAC address 00:A0:78:8E:9E:AA always receives the IP address 192.168.1.4.
host-name can also be used to assign a host name to the client.
host apex {
option host-name "apex.example.com";
hardware ethernet 00:A0:78:8E:9E:AA;
fixed-address 192.168.1.4;
}
shared-network declaration as shown in Example 12.4, “Shared-network declaration”. Parameters within the shared-network, but outside the enclosed subnet declarations, are considered to be global parameters. The name of the shared-network must be a descriptive title for the network, such as using the title 'test-lab' to describe all the subnets in a test lab environment.
group declaration is used to apply global parameters to a group of declarations. For example, shared networks, subnets, and hosts can be grouped.
group {
option routers 192.168.1.254;
option subnet-mask 255.255.255.0;
option domain-search "example.com";
option domain-name-servers 192.168.1.1;
option time-offset -18000; # Eastern Standard Time
host apex {
option host-name "apex.example.com";
hardware ethernet 00:A0:78:8E:9E:AA;
fixed-address 192.168.1.4;
}
host raleigh {
option host-name "raleigh.example.com";
hardware ethernet 00:A1:DD:74:C3:F2;
fixed-address 192.168.1.6;
}
}
cp /usr/share/doc/dhcp-<version-number>/dhcpd.conf.sample /etc/dhcp/dhcpd.conf<version-number> is the DHCP version number.
dhcp-options man page.
/var/lib/dhcpd/dhcpd.leases stores the DHCP client lease database. Do not change this file. DHCP lease information for each recently assigned IP address is automatically stored in the lease database. The information includes the length of the lease, to whom the IP address has been assigned, the start and end dates for the lease, and the MAC address of the network interface card that was used to retrieve the lease.
dhcpd.leases file is renamed dhcpd.leases~ and the temporary lease database is written to dhcpd.leases.
dhcpd.leases file does not exist, but it is required to start the service. Do not create a new lease file. If you do, all old leases are lost which causes many problems. The correct solution is to rename the dhcpd.leases~ backup file to dhcpd.leases and then start the daemon.
dhcpd.leases file exists. Use the command touch /var/lib/dhcpd/dhcpd.leases to create the file if it does not exist.
named service automatically checks for a dhcpd.leases file.
/sbin/service dhcpd start. To stop the DHCP server, use the command /sbin/service dhcpd stop.
/etc/sysconfig/dhcpd, add the name of the interface to the list of DHCPDARGS:
# Command line options here DHCPDARGS=eth0
/etc/sysconfig/dhcpd include:
-p <portnum> — Specifies the UDP port number on which dhcpd should listen. The default is port 67. The DHCP server transmits responses to the DHCP clients at a port number one greater than the UDP port specified. For example, if the default port 67 is used, the server listens on port 67 for requests and responses to the client on port 68. If a port is specified here and the DHCP relay agent is used, the same port on which the DHCP relay agent should listen must be specified. Refer to Section 12.2.4, “DHCP Relay Agent” for details.
-f — Runs the daemon as a foreground process. This is mostly used for debugging.
-d — Logs the DHCP server daemon to the standard error descriptor. This is mostly used for debugging. If this is not specified, the log is written to /var/log/messages.
-cf <filename> — Specifies the location of the configuration file. The default location is /etc/dhcp/dhcpd.conf.
-lf <filename> — Specifies the location of the lease database file. If a lease database file already exists, it is very important that the same file be used every time the DHCP server is started. It is strongly recommended that this option only be used for debugging purposes on non-production machines. The default location is /var/lib/dhcpd/dhcpd.leases.
-q — Do not print the entire copyright message when starting the daemon.
dhcrelay) allows for the relay of DHCP and BOOTP requests from a subnet with no DHCP server on it to one or more DHCP servers on other subnets.
/etc/sysconfig/dhcrelay with the INTERFACES directive.
service dhcrelay start.
/etc/sysconfig/network file to enable networking and the configuration file for each network device in the /etc/sysconfig/network-scripts directory. In this directory, each device should have a configuration file named ifcfg-eth0, where eth0 is the network device name.
/etc/sysconfig/network-scripts/ifcfg-eth0 file should contain the following lines:
DEVICE=eth0 BOOTPROTO=dhcp ONBOOT=yes
DHCP_HOSTNAME — Only use this option if the DHCP server requires the client to specify a hostname before receiving an IP address. (The DHCP server daemon in Red Hat Enterprise Linux does not support this feature.)
PEERDNS=<answer>, where <answer>yes — Modify /etc/resolv.conf with information from the server. If using DHCP, then yes is the default.
no — Do not modify /etc/resolv.conf.
dhclient and dhclient.conf man pages.
/etc/sysconfig/dhcpd and /etc/dhcp/dhcpd.conf files.
/etc/sysconfig/dhcpd file to specify which network interfaces the DHCP daemon listens on. The following /etc/sysconfig/dhcpd example specifies that the DHCP daemon listens on the eth0 and eth1 interfaces:
DHCPDARGS="eth0 eth1";
eth0, eth1, and eth2 -- and it is only desired that the DHCP daemon listens on eth0, then only specify eth0 in /etc/sysconfig/dhcpd:
DHCPDARGS="eth0";
/etc/dhcp/dhcpd.conf file, for a server that has two network interfaces, eth0 in a 10.0.0.0/24 network, and eth1 in a 172.16.0.0/24 network. Multiple subnet declarations allow different settings to be defined for multiple networks:
default-lease-time600; max-lease-time7200; subnet 10.0.0.0 netmask 255.255.255.0 { option subnet-mask 255.255.255.0; option routers 10.0.0.1; range 10.0.0.5 10.0.0.15; } subnet 172.16.0.0 netmask 255.255.255.0 { option subnet-mask 255.255.255.0; option routers 172.16.0.1; range 172.16.0.5 172.16.0.15; }
subnet 10.0.0.0 netmask 255.255.255.0; subnet declaration is required for every network your DHCP server is serving. Multiple subnets require multiple subnet declarations. If the DHCP server does not have a network interface in a range of a subnet declaration, the DHCP server does not serve that network.
subnet declaration, and no network interfaces are in the range of that subnet, the DHCP daemon fails to start, and an error such as the following is logged to /var/log/messages:
dhcpd: No subnet declaration for eth0 (0.0.0.0). dhcpd: ** Ignoring requests on eth0. If this is not what dhcpd: you want, please write a subnet declaration dhcpd: in your dhcpd.conf file for the network segment dhcpd: to which interface eth1 is attached. ** dhcpd: dhcpd: dhcpd: Not configured to listen on any interfaces!
option subnet-mask 255.255.255.0; option subnet-mask option defines a subnet mask, and overrides the netmask value in the subnet declaration. In simple cases, the subnet and netmask values are the same.
option routers 10.0.0.1; option routers option defines the default gateway for the subnet. This is required for systems to reach internal networks on a different subnet, as well as external networks.
range 10.0.0.5 10.0.0.15; range option specifies the pool of available IP addresses. Systems are assigned an address from the range of specified IP addresses.
dhcpd.conf(5) man page.
/etc/dhcp/dhcpd.conf, the DHCP daemon fails to start.
/etc/sysconfig/dhcpd and /etc/dhcp/dhcpd.conf files.
/etc/dhcp/dhcpd.conf example creates two subnets, and configures an IP address for the same system, depending on which network it connects to:
default-lease-time600; max-lease-time7200; subnet 10.0.0.0 netmask 255.255.255.0 { option subnet-mask 255.255.255.0; option routers 10.0.0.1; range 10.0.0.5 10.0.0.15; } subnet 172.16.0.0 netmask 255.255.255.0 { option subnet-mask 255.255.255.0; option routers 172.16.0.1; range 172.16.0.5 172.16.0.15; } host example0 { hardware ethernet 00:1A:6B:6A:2E:0B; fixed-address 10.0.0.20; } host example1 { hardware ethernet 00:1A:6B:6A:2E:0B; fixed-address 172.16.0.20; }
host example0 host declaration defines specific parameters for a single system, such as an IP address. To configure specific parameters for multiple hosts, use multiple host declarations.
host declarations, and as such, this name can anything, as long as it is unique to other host declarations. To configure the same system for multiple networks, use a different name for each host declaration, otherwise the DHCP daemon fails to start. Systems are identified by the hardware ethernet option, not the name in the host declaration.
hardware ethernet 00:1A:6B:6A:2E:0B; hardware ethernet option identifies the system. To find this address, run the ip link command.
fixed-address 10.0.0.20; fixed-address option assigns a valid IP address to the system specified by the hardware ethernet option. This address must be outside the IP address pool specified with the range option.
option statements do not end with a semicolon, the DHCP daemon fails to start, and an error such as the following is logged to /var/log/messages:
/etc/dhcp/dhcpd.conf line 20: semicolon expected. dhcpd: } dhcpd: ^ dhcpd: /etc/dhcp/dhcpd.conf line 38: unexpected end of file dhcpd: dhcpd: ^ dhcpd: Configuration file errors encountered -- exiting
host declarations configure a single system, that has multiple network interfaces, so that each interface receives the same IP address. This configuration will not work if both network interfaces are connected to the same network at the same time:
host interface0 {
hardware ethernet 00:1a:6b:6a:2e:0b;
fixed-address 10.0.0.18;
}
host interface1 {
hardware ethernet 00:1A:6B:6A:27:3A;
fixed-address 10.0.0.18;
}
interface0 is the first network interface, and interface1 is the second interface. The different hardware ethernet options identify each interface.
host declarations, remembering to:
fixed-address for the network the host is connecting to.
host declaration unique.
host declaration is not unique, the DHCP daemon fails to start, and an error such as the following is logged to /var/log/messages:
dhcpd: /etc/dhcp/dhcpd.conf line 31: host interface0: already exists dhcpd: } dhcpd: ^ dhcpd: Configuration file errors encountered -- exiting
host interface0 declarations defined in /etc/dhcp/dhcpd.conf.
/etc/dhcp/dhcpd6.conf.
/usr/share/doc/dhcp-<version>/dhcpd6.conf.sample.
/sbin/service dhcpd6 start.
subnet6 2001:db8:0:1::/64 {
range6 2001:db8:0:1::129 2001:db8:0:1::254;
option dhcp6.name-servers fec0:0:0:1::1;
option dhcp6.domain-search "domain.example";
}
dhcpd man page — Describes how the DHCP daemon works.
dhcpd.conf man page — Explains how to configure the DHCP configuration file; includes some examples.
dhcpd.leases man page — Describes a persistent database of leases.
dhcp-options man page — Explains the syntax for declaring DHCP options in dhcpd.conf; includes some examples.
dhcrelay man page — Explains the DHCP Relay Agent and its configuration options.
/usr/share/doc/dhcp-<version>/ — Contains sample files, README files, and release notes for current versions of the DHCP service.
DNS (Domain Name System), also known as a nameserver, is a network system that associates hostnames with their respective IP addresses. For users, this has the advantage that they can refer to machines on the network by names that are usually easier to remember than the numerical network addresses. For system administrators, using the nameserver allows them to change the IP address for a host without ever affecting the name-based queries, or to decide which machines handle these queries.
bob.sales.example.com
.). In Example 13.1, “A simple resource record”, com defines the top-level domain, example its subdomain, and sales the subdomain of example. In this case, bob identifies a resource record that is part of the sales.example.com domain. With the exception of the part furthest to the left (that is, bob), each of these sections is called a zone and defines a specific namespace.
named, an administration utility called rndc, and a debugging tool called dig. Refer to Chapter 9, Services and Daemons for more information on how to run a service in Red Hat Enterprise Linux.
BIND (Berkeley Internet Name Domain), the DNS server included in Red Hat Enterprise Linux. It focuses on the structure of its configuration files, and describes how to administer it both locally and remotely.
named service is started, it reads the configuration from the files as described in Table 13.1, “The named service configuration files”.
| Path | Description |
|---|---|
/etc/named.conf
| The main configuration file. |
/etc/named/
| An auxiliary directory for configuration files that are included in the main configuration file. |
{ and }). Note that when editing the file, you have to be careful not to make any syntax error, otherwise the named service will not start. A typical /etc/named.conf file is organized as follows:
statement-1["statement-1-name"] [statement-1-class] {option-1;option-2;option-N; };statement-2["statement-2-name"] [statement-2-class] {option-1;option-2;option-N; };statement-N["statement-N-name"] [statement-N-class] {option-1;option-2;option-N; };
/var/named/chroot environment. In that case, the initialization script will mount the above configuration files using the mount --bind command, so that you can manage the configuration outside this environment.
/etc/named.conf:
acl acl (Access Control List) statement allows you to define groups of hosts, so that they can be permitted or denied access to the nameserver. It takes the following form:
aclacl-name{match-element; ... };
acl-name statement name is the name of the access control list, and the match-element option is usually an individual IP address (such as 10.0.1.1) or a CIDR network notation (for example, 10.0.1.0/24). For a list of already defined keywords, see Table 13.2, “Predefined access control lists”.
| Keyword | Description |
|---|---|
any
| Matches every IP address. |
localhost
| Matches any IP address that is in use by the local system. |
localnets
| Matches any IP address on any network to which the local system is connected. |
none
| Does not match any IP address. |
acl statement can be especially useful with conjunction with other statements such as options. Example 13.2, “Using acl in conjunction with options” defines two access control lists, black-hats and red-hats, and adds black-hats on the blacklist while granting red-hats a normal access.
acl black-hats {
10.0.2.0/24;
192.168.0.0/24;
1234:5678::9abc/24;
};
acl red-hats {
10.0.1.0/24;
};
options {
blackhole { black-hats; };
allow-query { red-hats; };
allow-query-cache { red-hats; };
};include include statement allows you to include files in the /etc/named.conf, so that potentially sensitive data can be placed in a separate file with restricted permissions. It takes the following form:
include "file-name"file-name statement name is an absolute path to a file.
include "/etc/named.rfc1912.zones";
options options statement allows you to define global server configuration options as well as to set defaults for other statements. It can be used to specify the location of the named working directory, the types of queries allowed, and much more. It takes the following form:
options {
option;
...
};option directives, see Table 13.3, “Commonly used options” below.
| Option | Description |
|---|---|
allow-query
| Specifies which hosts are allowed to query the nameserver for authoritative resource records. It accepts an access control lists, a collection of IP addresses, or networks in the CIDR notation. All hosts are allowed by default. |
allow-query-cache
|
Specifies which hosts are allowed to query the nameserver for non-authoritative data such as recursive queries. Only localhost and localnets are allowed by default.
|
blackhole
|
Specifies which hosts are not allowed to query the nameserver. This option should be used when particular host or network floods the server with requests. The default option is none.
|
directory
|
Specifies a working directory for the named service. The default option is /var/named/.
|
dnssec-enable
|
Specifies whether to return DNSSEC related resource records. The default option is yes.
|
dnssec-validation
|
Specifies whether to prove that resource records are authentic via DNSSEC. The default option is yes.
|
forwarders
| Specifies a list of valid IP addresses for nameservers to which the requests should be forwarded for resolution. |
forward
|
Specifies the behavior of the
forwarders directive. It accepts the following options:
|
listen-on
| Specifies the IPv4 network interface on which to listen for queries. On a DNS server that also acts as a gateway, you can use this option to answer queries originating from a single network only. All IPv4 interfaces are used by default. |
listen-on-v6
| Specifies the IPv6 network interface on which to listen for queries. On a DNS server that also acts as a gateway, you can use this option to answer queries originating from a single network only. All IPv6 interfaces are used by default. |
max-cache-size
|
Specifies the maximum amount of memory to be used for server caches. When the limit is reached, the server causes records to expire prematurely so that the limit is not exceeded. In a server with multiple views, the limit applies separately to the cache of each view. The default option is 32M.
|
notify
|
Specifies whether to notify the secondary nameservers when a zone is updated. It accepts the following options:
|
pid-file
|
Specifies the location of the process ID file created by the named service.
|
recursion
|
Specifies whether to act as a recursive server. The default option is yes.
|
statistics-file
|
Specifies an alternate location for statistics files. The /var/named/named.stats file is used by default.
|
allow-query-cache option to restrict recursive DNS services for a particular subset of clients only.
named.conf manual page for a complete list of available options.
options {
allow-query { localhost; };
listen-on port 53 { 127.0.0.1; };
listen-on-v6 port 53 { ::1; };
max-cache-size 256M;
directory "/var/named";
statistics-file "/var/named/data/named_stats.txt";
recursion yes;
dnssec-enable yes;
dnssec-validation yes;
};zone zone statement allows you to define the characteristics of a zone, such as the location of its configuration file and zone-specific options, and can be used to override the global options statements. It takes the following form:
zonezone-name[zone-class] {option; ... };
zone-name attribute is the name of the zone, zone-class is the optional class of the zone, and option is a zone statement option as described in Table 13.4, “Commonly used options”.
zone-name attribute is particularly important, as it is the default value assigned for the $ORIGIN directive used within the corresponding zone file located in the /var/named/ directory. The named daemon appends the name of the zone to any non-fully qualified domain name listed in the zone file. For example, if a zone statement defines the namespace for example.com, use example.com as the zone-name so that it is placed at the end of hostnames within the example.com zone file.
| Option | Description |
|---|---|
allow-query
|
Specifies which clients are allowed to request information about this zone. This option overrides global allow-query option. All query requests are allowed by default.
|
allow-transfer
| Specifies which secondary servers are allowed to request a transfer of the zone's information. All transfer requests are allowed by default. |
allow-update
|
Specifies which hosts are allowed to dynamically update information in their zone. The default option is to deny all dynamic update requests.
Note that you should be careful when allowing hosts to update information about their zone. Do not set IP addresses in this option unless the server is in the trusted network. Instead, use TSIG key as described in Section 13.2.5.3, “Transaction SIGnatures (TSIG)”.
|
file
|
Specifies the name of the file in the named working directory that contains the zone's configuration data.
|
masters
|
Specifies from which IP addresses to request authoritative zone information. This option is used only if the zone is defined as type slave.
|
notify
|
Specifies whether to notify the secondary nameservers when a zone is updated. It accepts the following options:
|
type
|
Specifies the zone type. It accepts the following options:
|
/etc/named.conf file of a primary or secondary nameserver involve adding, modifying, or deleting zone statements, and only a small subset of zone statement options is usually needed for a nameserver to work efficiently.
example.com, the type is set to master, and the named service is instructed to read the /var/named/example.com.zone file. It also allows only a secondary nameserver (192.168.0.2) to transfer the zone.
zone "example.com" IN {
type master;
file "example.com.zone";
allow-transfer { 192.168.0.2; };
};zone statement is slightly different. The type is set to slave, and the masters directive is telling named the IP address of the master server.
named service is configured to query the primary server at the 192.168.0.1 IP address for information about the example.com zone. The received information is then saved to the /var/named/slaves/example.com.zone file. Note that you have to put all slave zones to /var/named/slaves directory, otherwise the service will fail to transfer the zone.
zone "example.com" {
type slave;
file "slaves/example.com.zone";
masters { 192.168.0.1; };
};/etc/named.conf:
controls controls statement allows you to configure various security requirements necessary to use the rndc command to administer the named service.
rndc utility and its usage.
key key statement allows you to define a particular key by name. Keys are used to authenticate various actions, such as secure updates or the use of the rndc command. Two options are used with key:
algorithm algorithm-name — The type of algorithm to be used (for example, hmac-md5).
secret "key-value" — The encrypted key.
rndc utility and its usage.
logging logging statement allows you to use multiple types of logs, so called channels. By using the channel option within the statement, you can construct a customized type of log with its own file name (file), size limit (size), versioning (version), and level of importance (severity). Once a customized channel is defined, a category option is used to categorize the channel and begin logging when the named service is restarted.
named sends standard messages to the rsyslog daemon, which places them in /var/log/messages. Several standard channels are built into BIND with various severity levels, such as default_syslog (which handles informational logging messages) and default_debug (which specifically handles debugging messages). A default category, called default, uses the built-in channels to do normal logging without any special configuration.
server server statement allows you to specify options that affect how the named service should respond to remote nameservers, especially with regard to notifications and zone transfers.
transfer-format option controls the number of resource records that are sent with each message. It can be either one-answer (only one resource record), or many-answers (multiple resource records). Note that while the many-answers option is more efficient, it is not supported by older versions of BIND.
trusted-keys trusted-keys statement allows you to specify assorted public keys used for secure DNS (DNSSEC). Refer to Section 13.2.5.4, “DNS Security Extensions (DNSSEC)” for more information on this topic.
view view statement allows you to create special views depending upon which network the host querying the nameserver is on. This allows some hosts to receive one answer regarding a zone while other hosts receive totally different information. Alternatively, certain zones may only be made available to particular trusted hosts while non-trusted hosts can only make queries for other zones.
match-clients option allows you to specify the IP addresses that apply to a particular view. If the options statement is used within a view, it overrides the already configured global options. Finally, most view statements contain multiple zone statements that apply to the match-clients list.
view statements are listed is important, as the first statement that matches a particular client's IP address is used. For more information on this topic, refer to Section 13.2.5.1, “Multiple Views”.
/etc/named.conf file can also contain comments. Comments are ignored by the named service, but can prove useful when providing additional information to a user. The following are valid comment tags:
//// characters to the end of the line is considered a comment. For example:
notify yes; // notify all secondary nameservers
## character to the end of the line is considered a comment. For example:
notify yes; # notify all secondary nameservers
/* and *//* and */ is considered a comment. For example:
notify yes; /* notify all secondary nameservers */
named working directory located in /var/named/ by default, and each zone file is named according to the file option in the zone statement, usually in a way that relates to the domain in question and identifies the file as containing zone data, such as example.com.zone.
| Path | Description |
|---|---|
/var/named/
|
The working directory for the named service. The nameserver is not allowed to write to this directory.
|
/var/named/slaves/
|
The directory for secondary zones. This directory is writable by the named service.
|
/var/named/dynamic/
|
The directory for other files, such as dynamic DNS (DDNS) zones or managed DNSSEC keys. This directory is writable by the named service.
|
/var/named/data/
|
The directory for various statistics and debugging files. This directory is writable by the named service.
|
$) followed by the name of the directive, and usually appear at the top of the file. The following directives are commonly used in zone files:
$INCLUDE $INCLUDE directive allows you to include another file at the place where it appears, so that other zone settings can be stored in a separate zone file.
$INCLUDE /var/named/penguin.example.com
$ORIGIN $ORIGIN directive allows you to append the domain name to unqualified records, such as those with the hostname only. Note that the use of this directive is not necessary if the zone is specified in /etc/named.conf, since the zone name is used by default.
. character) are appended with example.com.
$ORIGIN example.com.
$TTL $TTL directive allows you to set the default Time to Live (TTL) value for the zone, that is, how long is a zone record valid. Each resource record can contain its own TTL value, which overrides this directive.
$TTL 1D
A hostnameIN AIP-address
hostname value is omitted, the record will point to the last specified hostname.
server1.example.com are pointed to 10.0.1.3 or 10.0.1.5.
server1 IN A 10.0.1.3
IN A 10.0.1.5CNAME alias-nameIN CNAMEreal-name
CNAME records are most commonly used to point to services that use a common naming scheme, such as www for Web servers. However, there are multiple restrictions for their usage:
A record binds a hostname to an IP address, while the CNAME record points the commonly used www hostname to it.
server1 IN A 10.0.1.5 www IN CNAME server1
MX IN MXpreference-valueemail-server-name
email-server-name is a fully qualified domain name (FQDN). The preference-value allows numerical ranking of the email servers for a namespace, giving preference to some email systems over others. The MX resource record with the lowest preference-value is preferred over the others. However, multiple email servers can possess the same value to distribute email traffic evenly among them.
mail.example.com email server is preferred to the mail2.example.com email server when receiving email destined for the example.com domain.
example.com. IN MX 10 mail.example.com.
IN MX 20 mail2.example.com.NS IN NS nameserver-namenameserver-name should be a fully qualified domain name (FQDN). Note that when two nameservers are listed as authoritative for the domain, it is not important whether these nameservers are secondary nameservers, or if one of them is a primary server. They are both still considered authoritative.
IN NS dns1.example.com. IN NS dns2.example.com.
PTR last-IP-digitIN PTRFQDN-of-system
last-IP-digit directive is the last number in an IP address, and the FQDN-of-system is a fully qualified domain name (FQDN).
PTR records are primarily used for reverse name resolution, as they point IP addresses back to a particular name. Refer to Section 13.2.2.4.2, “A Reverse Name Resolution Zone File” for more examples of PTR records in use.
SOA @ IN SOAprimary-name-serverhostmaster-email(serial-numbertime-to-refreshtime-to-retrytime-to-expireminimum-TTL)
@ symbol places the $ORIGIN directive (or the zone's name if the $ORIGIN directive is not set) as the namespace being defined by this SOA resource record.
primary-name-server directive is the hostname of the primary nameserver that is authoritative for this domain.
hostmaster-email directive is the email of the person to contact about the namespace.
serial-number directive is a numerical value incremented every time the zone file is altered to indicate it is time for the named service to reload the zone.
time-to-refresh directive is the numerical value secondary nameservers use to determine how long to wait before asking the primary nameserver if any changes have been made to the zone.
time-to-retry directive is a numerical value used by secondary nameservers to determine the length of time to wait before issuing a refresh request in the event that the primary nameserver is not answering. If the primary server has not replied to a refresh request before the amount of time specified in the time-to-expire directive elapses, the secondary servers stop responding as an authority for requests concerning that namespace.
minimum-TTL directive is the amount of time other nameservers cache the zone's information. In BIND 9, it defines how long negative answers are cached for. Caching of negative answers can be set to a maximum of 3 hours (that is, 3H).
M), hours (H), days (D), and weeks (W). Table 13.6, “Seconds compared to other time units” shows an amount of time in seconds and the equivalent time in another format.
| Seconds | Other Time Units |
|---|---|
| 60 |
1M
|
| 1800 |
30M
|
| 3600 |
1H
|
| 10800 |
3H
|
| 21600 |
6H
|
| 43200 |
12H
|
| 86400 |
1D
|
| 259200 |
3D
|
| 604800 |
1W
|
| 31536000 |
365D
|
@ IN SOA dns1.example.com. hostmaster.example.com. (
2001062501 ; serial
21600 ; refresh after 6 hours
3600 ; retry after 1 hour
604800 ; expire after 1 week
86400 ) ; minimum TTL of 1 daynamed service, but can prove useful when providing additional information to the user. Any text after the semicolon character (that is, ;) to the end of the line is considered a comment. For example:
604800 ; expire after 1 week
SOA values.
$ORIGIN example.com.
$TTL 86400
@ IN SOA dns1.example.com. hostmaster.example.com. (
2001062501 ; serial
21600 ; refresh after 6 hours
3600 ; retry after 1 hour
604800 ; expire after 1 week
86400 ) ; minimum TTL of 1 day
;
;
IN NS dns1.example.com.
IN NS dns2.example.com.
dns1 IN A 10.0.1.1
IN AAAA aaaa:bbbb::1
dns2 IN A 10.0.1.2
IN AAAA aaaa:bbbb::2
;
;
@ IN MX 10 mail.example.com.
IN MX 20 mail2.example.com.
mail IN A 10.0.1.5
IN AAAA aaaa:bbbb::5
mail2 IN A 10.0.1.6
IN AAAA aaaa:bbbb::6
;
;
; This sample zone file illustrates sharing the same IP addresses
; for multiple services:
;
services IN A 10.0.1.10
IN AAAA aaaa:bbbb::10
IN A 10.0.1.11
IN AAAA aaaa:bbbb::11
ftp IN CNAME services.example.com.
www IN CNAME services.example.com.
;
;dns1.example.com and dns2.example.com, and are tied to the 10.0.1.1 and 10.0.1.2 IP addresses respectively using the A record.
MX records point to mail and mail2 via A records. Since these names do not end in a trailing period (that is, the . character), the $ORIGIN domain is placed after them, expanding them to mail.example.com and mail2.example.com.
www.example.com (WWW), are pointed at the appropriate servers using the CNAME record.
zone statement in the /etc/named.conf similar to the following:
zone "example.com" IN {
type master;
file "example.com.zone";
allow-update { none; };
};PTR resource records are used to link the IP addresses to a fully qualified domain name as shown in Example 13.16, “A reverse name resolution zone file”.
$ORIGIN 1.0.10.in-addr.arpa.
$TTL 86400
@ IN SOA dns1.example.com. hostmaster.example.com. (
2001062501 ; serial
21600 ; refresh after 6 hours
3600 ; retry after 1 hour
604800 ; expire after 1 week
86400 ) ; minimum TTL of 1 day
;
@ IN NS dns1.example.com.
;
1 IN PTR dns1.example.com.
2 IN PTR dns2.example.com.
;
5 IN PTR server1.example.com.
6 IN PTR server2.example.com.
;
3 IN PTR ftp.example.com.
4 IN PTR ftp.example.com.10.0.1.1 through 10.0.1.6 are pointed to the corresponding fully qualified domain name.
zone statement in the /etc/named.conf file similar to the following:
zone "1.0.10.in-addr.arpa" IN {
type master;
file "example.com.rr.zone";
allow-update { none; };
};zone statement, except for the zone name. Note that a reverse name resolution zone requires the first three blocks of the IP address reversed followed by .in-addr.arpa. This allows the single block of IP numbers used in the reverse name resolution zone file to be associated with the zone.
rndc utility is a command line tool that allows you to administer the named service, both locally and from a remote machine. Its usage is as follows:
rndc[option...]command[command-option]
named must be configured to listen on the selected port (that is, 953 by default), and an identical key must be used by both the service and the rndc utility.
rndc configuration is located in /etc/rndc.conf. If the file does not exist, the utility will use the key located in /etc/rndc.key, which was generated automatically during the installation process using the rndc-confgen -a command.
named service is configured using the controls statement in the /etc/named.conf configuration file as described in Section 13.2.1.2, “Other Statement Types”. Unless this statement is present, only the connections from the loopback address (that is, 127.0.0.1) will be allowed, and the key located in /etc/rndc.key will be used.
/etc/rndc.key file:
~]# chmod o-rwx /etc/rndc.keynamed service, use the following command:
~]# rndc status
version: 9.7.0-P2-RedHat-9.7.0-5.P2.el6
CPUs found: 1
worker threads: 1
number of zones: 16
debug level: 0
xfers running: 0
xfers deferred: 0
soa queries in progress: 0
query logging is OFF
recursive clients: 0/0/1000
tcp clients: 0/100
server is up and running~]# rndc reload
server reload successfulreload command, for example:
~]# rndc reload localhost
zone reload up-to-date~]# rndc reconfigfreeze command first:
~]# rndc freeze localhostthaw command to allow the DDNS again and reload the zone:
~]# rndc thaw localhost
The zone reload and thaw was successful.sign command. For example:
~]# rndc sign localhostauto-dnssec option has to be set to maintain in the zone statement. For instance:
zone "localhost" IN {
type master;
file "named.localhost";
allow-update { none; };
auto-dnssec maintain;
};~]# rndc validation on~]# rndc validation offoptions statement described in Section 13.2.1.1, “Common Statement Types” for information on how configure this option in /etc/named.conf.
~]# rndc querylogstatus command as described in Section 13.2.3.2, “Checking the Service Status”.
dig utility is a command line tool that allows you to perform DNS lookups and debug a nameserver configuration. Its typical usage is as follows:
dig[@server] [option...]nametype
types.
dignameNS
dig utility is used to display nameservers for example.com.
~]$ dig example.com NS
; <<>> DiG 9.7.1-P2-RedHat-9.7.1-2.P2.fc13 <<>> example.com NS
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 57883
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;example.com. IN NS
;; ANSWER SECTION:
example.com. 99374 IN NS a.iana-servers.net.
example.com. 99374 IN NS b.iana-servers.net.
;; Query time: 1 msec
;; SERVER: 10.34.255.7#53(10.34.255.7)
;; WHEN: Wed Aug 18 18:04:06 2010
;; MSG SIZE rcvd: 77dignameA
dig utility is used to display the IP address of example.com.
~]$ dig example.com A
; <<>> DiG 9.7.1-P2-RedHat-9.7.1-2.P2.fc13 <<>> example.com A
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 4849
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 0
;; QUESTION SECTION:
;example.com. IN A
;; ANSWER SECTION:
example.com. 155606 IN A 192.0.32.10
;; AUTHORITY SECTION:
example.com. 99175 IN NS a.iana-servers.net.
example.com. 99175 IN NS b.iana-servers.net.
;; Query time: 1 msec
;; SERVER: 10.34.255.7#53(10.34.255.7)
;; WHEN: Wed Aug 18 18:07:25 2010
;; MSG SIZE rcvd: 93dig-xaddress
dig utility is used to display the hostname assigned to 192.0.32.10.
~]$ dig -x 192.0.32.10
; <<>> DiG 9.7.1-P2-RedHat-9.7.1-2.P2.fc13 <<>> -x 192.0.32.10
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 29683
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 5, ADDITIONAL: 6
;; QUESTION SECTION:
;10.32.0.192.in-addr.arpa. IN PTR
;; ANSWER SECTION:
10.32.0.192.in-addr.arpa. 21600 IN PTR www.example.com.
;; AUTHORITY SECTION:
32.0.192.in-addr.arpa. 21600 IN NS b.iana-servers.org.
32.0.192.in-addr.arpa. 21600 IN NS c.iana-servers.net.
32.0.192.in-addr.arpa. 21600 IN NS d.iana-servers.net.
32.0.192.in-addr.arpa. 21600 IN NS ns.icann.org.
32.0.192.in-addr.arpa. 21600 IN NS a.iana-servers.net.
;; ADDITIONAL SECTION:
a.iana-servers.net. 13688 IN A 192.0.34.43
b.iana-servers.org. 5844 IN A 193.0.0.236
b.iana-servers.org. 5844 IN AAAA 2001:610:240:2::c100:ec
c.iana-servers.net. 12173 IN A 139.91.1.10
c.iana-servers.net. 12173 IN AAAA 2001:648:2c30::1:10
ns.icann.org. 12884 IN A 192.0.34.126
;; Query time: 156 msec
;; SERVER: 10.34.255.7#53(10.34.255.7)
;; WHEN: Wed Aug 18 18:25:15 2010
;; MSG SIZE rcvd: 310named service to provide name resolution services or to act as an authority for a particular domain. However, BIND version 9 has a number of advanced features that allow for a more secure and efficient DNS service.
view statement to the /etc/named.conf configuration file. Use the match-clients option to match IP addresses or entire networks and give them special options and zone data.
SERFVAIL response is returned for each resource record that fails the validation.
dig utility as described in Section 13.2.4, “Using the dig Utility”. Useful options are +dnssec (requests DNSSEC-related resource records by setting the DNSSEC OK bit), +cd (tells recursive nameserver not to validate the response), and +bufsize=512 (changes the packet size to 512B to get through some firewalls).
AAAA resource records, and the listen-on-v6 directive as described in Table 13.3, “Commonly used options”.
/etc/named.conf file can prevent the named service from starting.
. character) correctlynamed service will append the name of the zone or the value of $ORIGIN to complete it.
named service to other nameservers, the recommended best practice is to change the firewall settings whenever possible.
version with the version of the bind package installed on the system:
/usr/share/doc/bind-version//usr/share/doc/bind-version/arm//usr/share/doc/bind-version/draft//usr/share/doc/bind-version/misc/migration document for specific changes they must make when moving to BIND 9. The options file lists all of the options implemented in BIND 9 that are used in /etc/named.conf.
/usr/share/doc/bind-version/rfc/man rndcrndc containing the full documentation on its usage.
man namednamed containing the documentation on assorted arguments that can be used to control the BIND nameserver daemon.
man lwresdlwresd containing the full documentation on the lightweight resolver daemon and its usage.
man named.confnamed configuration file.
man rndc.confrndc configuration file.
HTTP (Hypertext Transfer Protocol) server, or a web server, is a network service that serves content to a client over the web. This typically means web pages, but any other documents can be served as well.
httpd service, and covers advanced topics such as adding server modules, setting up virtual hosts, or configuring the secure HTTP server.
httpd service configuration accordingly. This section reviews some of the newly added features, outlines important changes, and guides you through the update of older configuration files.
httpd service configuration:
LoadModule directive for each module that has been renamed.
/etc/httpd/conf.d/ssl.conf to enable the Secure Sockets Layer (SSL) protocol.
~]# service httpd configtest
Syntax OKhttpd service, make sure you have the httpd installed. You can do so by using the following command:
~]# yum install httpdhttpd service, type the following at a shell prompt:
~]# service httpd start
Starting httpd: [ OK ]~]# chkconfig httpd onhttpd service, type the following at a shell prompt:
~]# service httpd stop
Stopping httpd: [ OK ]~]# chkconfig httpd offhttpd service:
~]# service httpd restart
Stopping httpd: [ OK ]
Starting httpd: [ OK ]httpd service, and then start it again. Use this command after installing or removing a dynamically loaded module such as PHP.
~]# service httpd reloadhttpd service to reload the configuration file. Note that any requests being currently processed will be interrupted, which may cause a client browser to display an error message or render a partial page.
~]# service httpd gracefulhttpd service to reload the configuration file. Note that any requests being currently processed will use the old configuration.
~]# service httpd status
httpd (pid 19014) is running...httpd service is started, by default, it reads the configuration from locations that are listed in Table 14.1, “The httpd service configuration files”.
httpd service.
~]# service httpd configtest
Syntax OK/etc/httpd/conf/httpd.conf configuration file:
<Directory> <Directory> directive allows you to apply certain directives to a particular directory only. It takes the following form:
<Directorydirectory>directive… </Directory>
directory can be either a full path to an existing directory in the local file system, or a wildcard expression.
cgi-bin directories for server-side scripts located outside the directory that is specified by ScriptAlias. In this case, the ExecCGI and AddHandler directives must be supplied, and the permissions on the target directory must be set correctly (that is, 0755).
<Directory /var/www/html> Options Indexes FollowSymLinks AllowOverride None Order allow,deny Allow from all </Directory>
<IfDefine> IfDefine directive allows you to use certain directives only when a particular parameter is supplied on the command line. It takes the following form:
<IfDefine [!]parameter>directive… </IfDefine>
parameter can be supplied at a shell prompt using the -Dparameter command line option (for example, httpd -DEnableHome). If the optional exclamation mark (that is, !) is present, the enclosed directives are used only when the parameter is not specified.
<IfDefine EnableHome> UserDir public_html </IfDefine>
<IfModule> <IfModule> directive allows you to use certain directive only when a particular module is loaded. It takes the following form:
<IfModule [!]module>directive… </IfModule>
module can be identified either by its name, or by the file name. If the optional exclamation mark (that is, !) is present, the enclosed directives are used only when the module is not loaded.
<IfModule mod_disk_cache.c> CacheEnable disk / CacheRoot /var/cache/mod_proxy </IfModule>
<Location> <Location> directive allows you to apply certain directives to a particular URL only. It takes the following form:
<Locationurl>directive… </Location>
url can be either a path relative to the directory specified by the DocumentRoot directive (for example, /server-info), or an external URL such as http://example.com/server-info.
<Location /server-info> SetHandler server-info Order deny,allow Deny from all Allow from .example.com </Location>
<Proxy> <Proxy> directive allows you to apply certain directives to the proxy server only. It takes the following form:
<Proxypattern>directive… </Proxy>
pattern can be an external URL, or a wildcard expression (for example, http://example.com/*).
<Proxy *> Order deny,allow Deny from all Allow from .example.com </Proxy>
<VirtualHost> <VirtualHost> directive allows you apply certain directives to particular virtual hosts only. It takes the following form:
<VirtualHostaddress[:port]…>directive… </VirtualHost>
address can be an IP address, a fully qualified domain name, or a special form as described in Table 14.2, “Available <VirtualHost> options”.
| Option | Description |
|---|---|
*
| Represents all IP addresses. |
_default_
| Represents unmatched IP addresses. |
<VirtualHost *:80> ServerAdmin webmaster@penguin.example.com DocumentRoot /www/docs/penguin.example.com ServerName penguin.example.com ErrorLog logs/penguin.example.com-error_log CustomLog logs/penguin.example.com-access_log common </VirtualHost>
AccessFileName AccessFileName directive allows you to specify the file to be used to customize access control information for each directory. It takes the following form:
AccessFileName filename…filename is a name of the file to look for in the requested directory. By default, the server looks for .htaccess.
Files tag to prevent the files beginning with .ht from being accessed by web clients. This includes the .htaccess and .htpasswd files.
AccessFileName .htaccess <Files ~ "^\.ht"> Order allow,deny Deny from all Satisfy All </Files>
Action Action directive allows you to specify a CGI script to be executed when a certain media type is requested. It takes the following form:
Actioncontent-typepath
content-type has to be a valid MIME type such as text/html, image/png, or application/pdf. The path refers to an existing CGI script, and must be relative to the directory specified by the DocumentRoot directive (for example, /cgi-bin/process-image.cgi).
Action image/png /cgi-bin/process-image.cgi
AddDescription AddDescription directive allows you to specify a short description to be displayed in server-generated directory listings for a given file. It takes the following form:
AddDescription "description"filename…
description should be a short text enclosed in double quotes (that is, "). The filename can be a full file name, a file extension, or a wildcard expression.
AddDescription "GZIP compressed tar archive" .tgz
AddEncoding AddEncoding directive allows you to specify an encoding type for a particular file extension. It takes the following form:
AddEncodingencodingextension…
encoding has to be a valid MIME encoding such as x-compress, x-gzip, etc. The extension is a case sensitive file extension, and is conventionally written with a leading dot (for example, .gz).
AddEncoding x-gzip .gz .tgz
AddHandler AddHandler directive allows you to map certain file extensions to a selected handler. It takes the following form:
AddHandlerhandlerextension…
handler has to be a name of previously defined handler. The extension is a case sensitive file extension, and is conventionally written with a leading dot (for example, .cgi).
.cgi extension as CGI scripts regardless of the directory they are in. Additionally, it is also commonly used to process server-parsed HTML and image-map files.
AddHandler cgi-script .cgi
AddIcon AddIcon directive allows you to specify an icon to be displayed for a particular file in server-generated directory listings. It takes the following form:
AddIconpathpattern…
path refers to an existing icon file, and must be relative to the directory specified by the DocumentRoot directive (for example, /icons/folder.png). The pattern can be a file name, a file extension, a wildcard expression, or a special form as described in the following table:
| Option | Description |
|---|---|
^^DIRECTORY^^
| Represents a directory. |
^^BLANKICON^^
| Represents a blank line. |
AddIcon /icons/text.png .txt README
AddIconByEncoding AddIconByEncoding directive allows you to specify an icon to be displayed for a particular encoding type in server-generated directory listings. It takes the following form:
AddIconByEncodingpathencoding…
path refers to an existing icon file, and must be relative to the directory specified by the DocumentRoot directive (for example, /icons/compressed.png). The encoding has to be a valid MIME encoding such as x-compress, x-gzip, etc.
AddIconByEncoding /icons/compressed.png x-compress x-gzip
AddIconByType AddIconByType directive allows you to specify an icon to be displayed for a particular media type in server-generated directory listings. It takes the following form:
AddIconByTypepathcontent-type…
path refers to an existing icon file, and must be relative to the directory specified by the DocumentRoot directive (for example, /icons/text.png). The content-type has to be either a valid MIME type (for example, text/html or image/png), or a wildcard expression such as text/*, image/*, etc.
AddIconByType /icons/video.png video/*
AddLanguage AddLanguage directive allows you to associate a file extension with a specific language. It takes the following form:
AddLanguagelanguageextension…
language has to be a valid MIME language such as cs, en, or fr. The extension is a case sensitive file extension, and is conventionally written with a leading dot (for example, .cs).
AddLanguage cs .cs .cz
AddType AddType directive allows you to define or override the media type for a particular file extension. It takes the following form:
AddTypecontent-typeextension…
content-type has to be a valid MIME type such as text/html, image/png, etc. The extension is a case sensitive file extension, and is conventionally written with a leading dot (for example, .cs).
AddType application/x-gzip .gz .tgz
Alias Alias directive allows you to refer to files and directories outside the default directory specified by the DocumentRoot directive. It takes the following form:
Aliasurl-pathreal-path
url-path must be relative to the directory specified by the DocumentRoot directive (for example, /images/). The real-path is a full path to a file or directory in the local file system.
Directory tag with additional permissions to access the target directory. By default, the /icons/ alias is created so that the icons from /var/www/icons/ are displayed in server-generated directory listings.
Alias /icons/ /var/www/icons/ <Directory "/var/www/icons"> Options Indexes MultiViews FollowSymLinks AllowOverride None Order allow,deny Allow from all <Directory>
AllowAllow directive allows you to specify which clients have permission to access a given directory. It takes the following form:
Allow from client…client can be a domain name, an IP address (both full and partial), a network/netmask pair, or all for all clients.
Allow from 192.168.1.0/255.255.255.0
AllowOverride AllowOverride directive allows you to specify which directives in a .htaccess file can override the default configuration. It takes the following form:
AllowOverride type…type has to be one of the available grouping options as described in Table 14.4, “Available AllowOverride options”.
| Option | Description |
|---|---|
All
|
All directives in .htaccess are allowed to override earlier configuration settings.
|
None
|
No directive in .htaccess is allowed to override earlier configuration settings.
|
AuthConfig
|
Allows the use of authorization directives such as AuthName, AuthType, or Require.
|
FileInfo
|
Allows the use of file type, metadata, and mod_rewrite directives such as DefaultType, RequestHeader, or RewriteEngine, as well as the Action directive.
|
Indexes
|
Allows the use of directory indexing directives such as AddDescription, AddIcon, or FancyIndexing.
|
Limit
|
Allows the use of host access directives, that is, Allow, Deny, and Order.
|
Options[=option,…]
|
Allows the use of the Options directive. Additionally, you can provide a comma-separated list of options to customize which options can be set using this directive.
|
AllowOverride FileInfo AuthConfig Limit
BrowserMatch BrowserMatch directive allows you to modify the server behavior based on the client's web browser type. It takes the following form:
BrowserMatchpatternvariable…
pattern is a regular expression to match the User-Agent HTTP header field. The variable is an environment variable that is set when the header field matches the pattern.
BrowserMatch "Mozilla/2" nokeepalive
CacheDefaultExpire CacheDefaultExpire option allows you to set how long to cache a document that does not have any expiration date or the date of its last modification specified. It takes the following form:
CacheDefaultExpire timetime is specified in seconds. The default option is 3600 (that is, one hour).
CacheDefaultExpire 3600
CacheDisable CacheDisable directive allows you to disable caching of certain URLs. It takes the following form:
CacheDisable pathpath must be relative to the directory specified by the DocumentRoot directive (for example, /files/).
CacheDisable /temporary
CacheEnable CacheEnable directive allows you to specify a cache type to be used for certain URLs. It takes the following form:
CacheEnabletypeurl
type has to be a valid cache type as described in Table 14.5, “Available cache types”. The url can be a path relative to the directory specified by the DocumentRoot directive (for example, /images/), a protocol (for example, ftp://), or an external URL such as http://example.com/.
| Type | Description |
|---|---|
mem
| The memory-based storage manager. |
disk
| The disk-based storage manager. |
fd
| The file descriptor cache. |
CacheEnable disk /
CacheLastModifiedFactor CacheLastModifiedFactor directive allows you to customize how long to cache a document that does not have any expiration date specified, but that provides information about the date of its last modification. It takes the following form:
CacheLastModifiedFactor numbernumber is a coefficient to be used to multiply the time that passed since the last modification of the document. The default option is 0.1 (that is, one tenth).
CacheLastModifiedFactor 0.1
CacheMaxExpire CacheMaxExpire directive allows you to specify the maximum amount of time to cache a document. It takes the following form:
CacheMaxExpire timetime is specified in seconds. The default option is 86400 (that is, one day).
CacheMaxExpire 86400
CacheNegotiatedDocs CacheNegotiatedDocs directive allows you to enable caching of the documents that were negotiated on the basis of content. It takes the following form:
CacheNegotiatedDocs optionoption has to be a valid keyword as described in Table 14.6, “Available CacheNegotiatedDocs options”. Since the content-negotiated documents may change over time or because of the input from the requester, the default option is Off.
| Option | Description |
|---|---|
On
| Enables caching the content-negotiated documents. |
Off
| Disables caching the content-negotiated documents. |
CacheNegotiatedDocs On
CacheRoot CacheRoot directive allows you to specify the directory to store cache files in. It takes the following form:
CacheRoot directorydirectory must be a full path to an existing directory in the local file system. The default option is /var/cache/mod_proxy/.
CacheRoot /var/cache/mod_proxy
CustomLog CustomLog directive allows you to specify the log file name and the log file format. It takes the following form:
CustomLogpathformat
path refers to a log file, and must be relative to the directory that is specified by the ServerRoot directive (that is, /etc/httpd/ by default). The format has to be either an explicit format string, or a format name that was previously defined using the LogFormat directive.
CustomLog logs/access_log combined
DefaultIcon DefaultIcon directive allows you to specify an icon to be displayed for a file in server-generated directory listings when no other icon is associated with it. It takes the following form:
DefaultIcon pathpath refers to an existing icon file, and must be relative to the directory specified by the DocumentRoot directive (for example, /icons/unknown.png).
DefaultIcon /icons/unknown.png
DefaultType DefaultType directive allows you to specify a media type to be used in case the proper MIME type cannot be determined by the server. It takes the following form:
DefaultType content-typecontent-type has to be a valid MIME type such as text/html, image/png, application/pdf, etc.
DefaultType text/plain
Deny Deny directive allows you to specify which clients are denied access to a given directory. It takes the following form:
Deny from client…client can be a domain name, an IP address (both full and partial), a network/netmask pair, or all for all clients.
Deny from 192.168.1.1
DirectoryIndex DirectoryIndex directive allows you to specify a document to be served to a client when a directory is requested (that is, when the URL ends with the / character). It takes the following form:
DirectoryIndex filename…filename is a name of the file to look for in the requested directory. By default, the server looks for index.html, and index.html.var.
DirectoryIndex index.html index.html.var
DocumentRoot DocumentRoot directive allows you to specify the main directory from which the content is served. It takes the following form:
DocumentRoot directorydirectory must be a full path to an existing directory in the local file system. The default option is /var/www/html/.
DocumentRoot /var/www/html
ErrorDocument ErrorDocument directive allows you to specify a document or a message to be displayed as a response to a particular error. It takes the following form:
ErrorDocumenterror-codeaction
error-code has to be a valid code such as 403 (Forbidden), 404 (Not Found), or 500 (Internal Server Error). The action can be either a URL (both local and external), or a message string enclosed in double quotes (that is, ").
ErrorDocument 403 "Access Denied" ErrorDocument 404 /404-not_found.html
ErrorLog ErrorLog directive allows you to specify a file to which the server errors are logged. It takes the following form:
ErrorLog pathpath refers to a log file, and can be either absolute, or relative to the directory that is specified by the ServerRoot directive (that is, /etc/httpd/ by default). The default option is logs/error_log
ErrorLog logs/error_log
ExtendedStatus ExtendedStatus directive allows you to enable detailed server status information. It takes the following form:
ExtendedStatus optionoption has to be a valid keyword as described in Table 14.7, “Available ExtendedStatus options”. The default option is Off.
| Option | Description |
|---|---|
On
| Enables generating the detailed server status. |
Off
| Disables generating the detailed server status. |
ExtendedStatus On
Group Group directive allows you to specify the group under which the httpd service will run. It takes the following form:
Group groupgroup has to be an existing UNIX group. The default option is apache.
Group is no longer supported inside <VirtualHost>, and has been replaced by the SuexecUserGroup directive.
Group apache
HeaderName HeaderName directive allows you to specify a file to be prepended to the beginning of the server-generated directory listing. It takes the following form:
HeaderName filenamefilename is a name of the file to look for in the requested directory. By default, the server looks for HEADER.html.
HeaderName HEADER.html
HostnameLookups HostnameLookups directive allows you to enable automatic resolving of IP addresses. It takes the following form:
HostnameLookups optionoption has to be a valid keyword as described in Table 14.8, “Available HostnameLookups options”. To conserve resources on the server, the default option is Off.
| Option | Description |
|---|---|
On
| Enables resolving the IP address for each connection so that the hostname can be logged. However, this also adds a significant processing overhead. |
Double
| Enables performing the double-reverse DNS lookup. In comparison to the above option, this adds even more processing overhead. |
Off
| Disables resolving the IP address for each connection. |
HostnameLookups Off
Include Include directive allows you to include other configuration files. It takes the following form:
Include filenamefilename can be an absolute path, a path relative to the directory specified by the ServerRoot directive, or a wildcard expression. All configuration files from the /etc/httpd/conf.d/ directory are loaded by default.
Include conf.d/*.conf
IndexIgnore IndexIgnore directive allows you to specify a list of file names to be omitted from the server-generated directory listings. It takes the following form:
IndexIgnore filename…filename option can be either a full file name, or a wildcard expression.
IndexIgnore .??* *~ *# HEADER* README* RCS CVS *,v *,t
IndexOptions IndexOptions directive allows you to customize the behavior of server-generated directory listings. It takes the following form:
IndexOptions option…option has to be a valid keyword as described in Table 14.9, “Available directory listing options”. The default options are Charset=UTF-8, FancyIndexing, HTMLTable, NameWidth=*, and VersionSort.
| Option | Description |
|---|---|
Charset=encoding
|
Specifies the character set of a generated web page. The encoding has to be a valid character set such as UTF-8 or ISO-8859-2.
|
Type=content-type
|
Specifies the media type of a generated web page. The content-type has to be a valid MIME type such as text/html or text/plain.
|
DescriptionWidth=value
|
Specifies the width of the description column. The value can be either a number of characters, or an asterisk (that is, *) to adjust the width automatically.
|
FancyIndexing
| Enables advanced features such as different icons for certain files or possibility to re-sort a directory listing by clicking on a column header. |
FolderFirst
| Enables listing directories first, always placing them above files. |
HTMLTable
| Enables the use of HTML tables for directory listings. |
IconsAreLinks
| Enables using the icons as links. |
IconHeight=value
|
Specifies an icon height. The value is a number of pixels.
|
IconWidth=value
|
Specifies an icon width. The value is a number of pixels.
|
IgnoreCase
| Enables sorting files and directories in a case-sensitive manner. |
IgnoreClient
| Disables accepting query variables from a client. |
NameWidth=value
|
Specifies the width of the file name column. The value can be either a number of characters, or an asterisk (that is, *) to adjust the width automatically.
|
ScanHTMLTitles
|
Enables parsing the file for a description (that is, the title element) in case it is not provided by the AddDescription directive.
|
ShowForbidden
| Enables listing the files with otherwise restricted access. |
SuppressColumnSorting
| Disables re-sorting a directory listing by clicking on a column header. |
SuppressDescription
| Disables reserving a space for file descriptions. |
SuppressHTMLPreamble
|
Disables the use of standard HTML preamble when a file specified by the HeaderName directive is present.
|
SuppressIcon
| Disables the use of icons in directory listings. |
SuppressLastModified
| Disables displaying the date of the last modification field in directory listings. |
SuppressRules
| Disables the use of horizontal lines in directory listings. |
SuppressSize
| Disables displaying the file size field in directory listings. |
TrackModified
|
Enables returning the Last-Modified and ETag values in the HTTP header.
|
VersionSort
| Enables sorting files that contain a version number in the expected manner. |
XHTML
| Enables the use of XHTML 1.0 instead of the default HTML 3.2. |
IndexOptions FancyIndexing VersionSort NameWidth=* HTMLTable Charset=UTF-8
KeepAlive KeepAlive directive allows you to enable persistent connections. It takes the following form:
KeepAlive optionoption has to be a valid keyword as described in Table 14.10, “Available KeepAlive options”. The default option is Off.
| Option | Description |
|---|---|
On
| Enables the persistent connections. In this case, the server will accept more than one request per connection. |
Off
| Disables the keep-alive connections. |
KeepAliveTimeout to a low number, and monitor the /var/log/httpd/logs/error_log log file carefully.
KeepAlive Off
KeepAliveTimeout KeepAliveTimeout directive allows you to specify the amount of time to wait for another request before closing the connection. It takes the following form:
KeepAliveTimeout timetime is specified in seconds. The default option is 15.
KeepAliveTimeout 15
LanguagePriority LanguagePriority directive allows you to customize the precedence of languages. It takes the following form:
LanguagePriority language…language has to be a valid MIME language such as cs, en, or fr.
LanguagePriority sk cs en
Listen Listen directive allows you to specify IP addresses or ports to listen to. It takes the following form:
Listen [ip-address:]port[protocol]
ip-address is optional and unless supplied, the server will accept incoming requests on a given port from all IP addresses. Since the protocol is determined automatically from the port number, it can be usually omitted. The default option is to listen to port 80.
httpd service.
Listen 80
LoadModule LoadModule directive allows you to load a Dynamic Shared Object (DSO) module. It takes the following form:
LoadModulenamepath
name has to be a valid identifier of the required module. The path refers to an existing module file, and must be relative to the directory in which the libraries are placed (that is, /usr/lib/httpd/ on 32-bit and /usr/lib64/httpd/ on 64-bit systems by default).
LoadModule php5_module modules/libphp5.so
LogFormat LogFormat directive allows you to specify a log file format. It takes the following form:
LogFormatformatname
format is a string consisting of options as described in Table 14.11, “Common LogFormat options”. The name can be used instead of the format string in the CustomLog directive.
| Option | Description |
|---|---|
%b
| Represents the size of the response in bytes. |
%h
| Represents the IP address or hostname of a remote client. |
%l
|
Represents the remote log name if supplied. If not, a hyphen (that is, -) is used instead.
|
%r
| Represents the first line of the request string as it came from the browser or client. |
%s
| Represents the status code. |
%t
| Represents the date and time of the request. |
%u
|
If the authentication is required, it represents the remote user. If not, a hyphen (that is, -) is used instead.
|
%{
|
Represents the content of the HTTP header field. The common options include %{Referer} (the URL of the web page that referred the client to the server) and %{User-Agent} (the type of the web browser making the request).
|
LogFormat "%h %l %u %t \"%r\" %>s %b" common
LogLevel LogLevel directive allows you to customize the verbosity level of the error log. It takes the following form:
LogLevel optionoption has to be a valid keyword as described in Table 14.12, “Available LogLevel options”. The default option is warn.
| Option | Description |
|---|---|
emerg
| Only the emergency situations when the server cannot perform its work are logged. |
alert
| All situations when an immediate action is required are logged. |
crit
| All critical conditions are logged. |
error
| All error messages are logged. |
warn
| All warning messages are logged. |
notice
| Even normal, but still significant situations are logged. |
info
| Various informational messages are logged. |
debug
| Various debugging messages are logged. |
LogLevel warn
MaxKeepAliveRequests MaxKeepAliveRequests directive allows you to specify the maximum number of requests for a persistent connection. It takes the following form:
MaxKeepAliveRequests numbernumber can improve the performance of the server. Note that using 0 allows unlimited number of requests. The default option is 100.
MaxKeepAliveRequests 100
NameVirtualHost NameVirtualHost directive allows you to specify the IP address and port number for a name-based virtual host. It takes the following form:
NameVirtualHostip-address[:port]
ip-address can be either a full IP address, or an asterisk (that is, *) representing all interfaces. Note that IPv6 addresses have to be enclosed in square brackets (that is, [ and ]). The port is optional.
NameVirtualHost *:80
Options Options directive allows you to specify which server features are available in a particular directory. It takes the following form:
Options option…option has to be a valid keyword as described in Table 14.13, “Available server features”.
| Option | Description |
|---|---|
ExecCGI
| Enables the execution of CGI scripts. |
FollowSymLinks
| Enables following symbolic links in the directory. |
Includes
| Enables server-side includes. |
IncludesNOEXEC
| Enables server-side includes, but does not allow the execution of commands. |
Indexes
| Enables server-generated directory listings. |
MultiViews
| Enables content-negotiated “MultiViews”. |
SymLinksIfOwnerMatch
| Enables following symbolic links in the directory when both the link and the target file have the same owner. |
All
|
Enables all of the features above with the exception of MultiViews.
|
None
| Disables all of the features above. |
Options Indexes FollowSymLinks
Order Order directive allows you to specify the order in which the Allow and Deny directives are evaluated. It takes the following form:
Order optionoption has to be a valid keyword as described in Table 14.14, “Available Order options”. The default option is allow,deny.
| Option | Description |
|---|---|
allow,deny
|
Allow directives are evaluated first.
|
deny,allow
|
Deny directives are evaluated first.
|
Order allow,deny
PidFile PidFile directive allows you to specify a file to which the process ID (PID) of the server is stored. It takes the following form:
PidFile pathpath refers to a pid file, and can be either absolute, or relative to the directory that is specified by the ServerRoot directive (that is, /etc/httpd/ by default). The default option is run/httpd.pid.
PidFile run/httpd.pid
ProxyRequests ProxyRequests directive allows you to enable forward proxy requests. It takes the following form:
ProxyRequests optionoption has to be a valid keyword as described in Table 14.15, “Available ProxyRequests options”. The default option is Off.
| Option | Description |
|---|---|
On
| Enables forward proxy requests. |
Off
| Disables forward proxy requests. |
ProxyRequests On
ReadmeName ReadmeName directive allows you to specify a file to be appended to the end of the server-generated directory listing. It takes the following form:
ReadmeName filenamefilename is a name of the file to look for in the requested directory. By default, the server looks for README.html.
ReadmeName README.html
Redirect Redirect directive allows you to redirect a client to another URL. It takes the following form:
Redirect [status]pathurl
status is optional, and if provided, it has to be a valid keyword as described in Table 14.16, “Available status options”. The path refers to the old location, and must be relative to the directory specified by the DocumentRoot directive (for example, /docs). The url refers to the current location of the content (for example, http://docs.example.com).
| Status | Description |
|---|---|
permanent
|
Indicates that the requested resource has been moved permanently. The 301 (Moved Permanently) status code is returned to a client.
|
temp
|
Indicates that the requested resource has been moved only temporarily. The 302 (Found) status code is returned to a client.
|
seeother
|
Indicates that the requested resource has been replaced. The 303 (See Other) status code is returned to a client.
|
gone
|
Indicates that the requested resource has been removed permanently. The 410 (Gone) status is returned to a client.
|
mod_rewrite module that is part of the Apache HTTP Server installation.
Redirect permanent /docs http://docs.example.com
ScriptAlias ScriptAlias directive allows you to specify the location of CGI scripts. It takes the following form:
ScriptAliasurl-pathreal-path
url-path must be relative to the directory specified by the DocumentRoot directive (for example, /cgi-bin/). The real-path is a full path to a file or directory in the local file system.
Directory tag with additional permissions to access the target directory. By default, the /cgi-bin/ alias is created so that the scripts located in the /var/www/cgi-bin/ are accessible.
ScriptAlias directive is used for security reasons to prevent CGI scripts from being viewed as ordinary text documents.
ScriptAlias /cgi-bin/ /var/www/cgi-bin/ <Directory "/var/www/cgi-bin"> AllowOverride None Options None Order allow,deny Allow from all </Directory>
ServerAdmin ServerAdmin directive allows you to specify the email address of the server administrator to be displayed in server-generated web pages. It takes the following form:
ServerAdmin emailroot@localhost.
webmaster@hostname, where hostname is the address of the server. Once set, alias webmaster to the person responsible for the web server in /etc/aliases, and as superuser, run the newaliases command.
ServerAdmin webmaster@penguin.example.com
ServerName ServerName directive allows you to specify the hostname and the port number of a web server. It takes the following form:
ServerNamehostname[:port]
hostname has to be a fully qualified domain name (FQDN) of the server. The port is optional, but when supplied, it has to match the number specified by the Listen directive.
/etc/hosts file.
ServerName penguin.example.com:80
ServerRoot ServerRoot directive allows you to specify the directory in which the server operates. It takes the following form:
ServerRoot directorydirectory must be a full path to an existing directory in the local file system. The default option is /etc/httpd/.
ServerRoot /etc/httpd
ServerSignature ServerSignature directive allows you to enable displaying information about the server on server-generated documents. It takes the following form:
ServerSignature optionoption has to be a valid keyword as described in Table 14.17, “Available ServerSignature options”. The default option is On.
| Option | Description |
|---|---|
On
| Enables appending the server name and version to server-generated pages. |
Off
| Disables appending the server name and version to server-generated pages. |
EMail
|
Enables appending the server name, version, and the email address of the system administrator as specified by the ServerAdmin directive to server-generated pages.
|
ServerSignature On
ServerTokens ServerTokens directive allows you to customize what information are included in the Server response header. It takes the following form:
ServerTokens optionoption has to be a valid keyword as described in Table 14.18, “Available ServerTokens options”. The default option is OS.
| Option | Description |
|---|---|
Prod
|
Includes the product name only (that is, Apache).
|
Major
|
Includes the product name and the major version of the server (for example, 2).
|
Minor
|
Includes the product name and the minor version of the server (for example, 2.2).
|
Min
|
Includes the product name and the minimal version of the server (for example, 2.2.15).
|
OS
|
Includes the product name, the minimal version of the server, and the type of the operating system it is running on (for example, Red Hat).
|
Full
| Includes all the information above along with the list of loaded modules. |
ServerTokens Prod
SuexecUserGroup SuexecUserGroup directive allows you to specify the user and group under which the CGI scripts will be run. It takes the following form:
SuexecUserGroupusergroup
user has to be an existing user, and the group must be a valid UNIX group.
<VirtualHost>, SuexecUserGroup replaces the User and Group directives.
SuexecUserGroup apache apache
Timeout Timeout directive allows you to specify the amount of time to wait for an event before closing a connection. It takes the following form:
Timeout timetime is specified in seconds. The default option is 60.
Timeout 60
TypesConfig TypesConfig allows you to specify the location of the MIME types configuration file. It takes the following form:
TypesConfig pathpath refers to an existing MIME types configuration file, and can be either absolute, or relative to the directory that is specified by the ServerRoot directive (that is, /etc/httpd/ by default). The default option is /etc/mime.types.
/etc/mime.types, the recommended way to add MIME type mapping to the Apache HTTP Server is to use the AddType directive.
TypesConfig /etc/mime.types
UseCanonicalName UseCanonicalName allows you to specify the way the server refers to itself. It takes the following form:
UseCanonicalName optionoption has to be a valid keyword as described in Table 14.19, “Available UseCanonicalName options”. The default option is Off.
| Option | Description |
|---|---|
On
|
Enables the use of the name that is specified by the ServerName directive.
|
Off
|
Disables the use of the name that is specified by the ServerName directive. The hostname and port number provided by the requesting client are used instead.
|
DNS
|
Disables the use of the name that is specified by the ServerName directive. The hostname determined by a reverse DNS lookup is used instead.
|
UseCanonicalName Off
User User directive allows you to specify the user under which the httpd service will run. It takes the following form:
User useruser has to be an existing UNIX user. The default option is apache.
httpd service should not be run with root privileges. Note that User is no longer supported inside <VirtualHost>, and has been replaced by the SuexecUserGroup directive.
User apache
UserDir UserDir directive allows you to enable serving content from users' home directories. It takes the following form:
UserDir optionoption can be either a name of the directory to look for in user's home directory (typically public_html), or a valid keyword as described in Table 14.20, “Available UserDir options”. The default option is disabled.
| Option | Description |
|---|---|
enabled user…
|
Enables serving content from home directories of given users.
|
disabled [user…]
|
Disables serving content from home directories, either for all users, or, if a space separated list of users is supplied, for given users only.
|
UserDir directive. For example:
~]#chmod a+x /home/~]#username/chmod a+rx /home/username/public_html/
UserDir public_html
/etc/httpd/conf.d/ssl.conf:
SetEnvIf SetEnvIf directive allows you to set environment variables based on the headers of incoming connections. It takes the following form:
SetEnvIfoptionpattern[!]variable[=value]…
option can be either a HTTP header field, a previously defined environment variable name, or a valid keyword as described in Table 14.21, “Available SetEnvIf options”. The pattern is a regular expression. The variable is an environment variable that is set when the option matches the pattern. If the optional exclamation mark (that is, !) is present, the variable is removed instead of being set.
| Option | Description |
|---|---|
Remote_Host
| Refers to the client's hostname. |
Remote_Addr
| Refers to the client's IP address. |
Server_Addr
| Refers to the server's IP address. |
Request_Method
|
Refers to the request method (for example, GET).
|
Request_Protocol
|
Refers to the protocol name and version (for example, HTTP/1.1).
|
Request_URI
| Refers to the requested resource. |
SetEnvIf directive is used to disable HTTP keepalives, and to allow SSL to close the connection without a closing notification from the client browser. This is necessary for certain web browsers that do not reliably shut down the SSL connection.
SetEnvIf User-Agent ".*MSIE.*" \
nokeepalive ssl-unclean-shutdown \
downgrade-1.0 force-response-1.0/etc/httpd/conf.d/ssl.conf file to be present, the mod_ssl needs to be installed. Refer to Section 14.1.8, “Setting Up an SSL Server” for more information on how to install and configure an SSL server.
IfModule. By default, the server-pool is defined for both the prefork and worker MPMs.
/etc/httpd/conf/httpd.conf:
MaxClients MaxClients directive allows you to specify the maximum number of simultaneously connected clients to process at one time. It takes the following form:
MaxClients numbernumber can improve the performance of the server, although it is not recommended to exceed 256 when using the prefork MPM.
MaxClients 256
MaxRequestsPerChild MaxRequestsPerChild directive allows you to specify the maximum number of request a child process can serve before it dies. It takes the following form:
MaxRequestsPerChild numbernumber to 0 allows unlimited number of requests.
MaxRequestsPerChild directive is used to prevent long-lived processes from causing memory leaks.
MaxRequestsPerChild 4000
MaxSpareServers MaxSpareServers directive allows you to specify the maximum number of spare child processes. It takes the following form:
MaxSpareServers numberprefork MPM only.
MaxSpareServers 20
MaxSpareThreads MaxSpareThreads directive allows you to specify the maximum number of spare server threads. It takes the following form:
MaxSpareThreads numbernumber must be greater than or equal to the sum of MinSpareThreads and ThreadsPerChild. This directive is used by the worker MPM only.
MaxSpareThreads 75
MinSpareServers MinSpareServers directive allows you to specify the minimum number of spare child processes. It takes the following form:
MinSpareServers numbernumber can create a heavy processing load on the server. This directive is used by the prefork MPM only.
MinSpareServers 5
MinSpareThreads MinSpareThreads directive allows you to specify the minimum number of spare server threads. It takes the following form:
MinSpareThreads numberworker MPM only.
MinSpareThreads 75
StartServers StartServers directive allows you to specify the number of child processes to create when the service is started. It takes the following form:
StartServers numberStartServers 8
ThreadsPerChild ThreadsPerChild directive allows you to specify the number of threads a child process can create. It takes the following form:
ThreadsPerChild numberworker MPM only.
ThreadsPerChild 25
httpd service is distributed along with a number of Dynamic Shared Objects (DSOs), which can be dynamically loaded or unloaded at runtime as necessary. By default, these modules are located in /usr/lib/httpd/modules/ on 32-bit and in /usr/lib64/httpd/modules/ on 64-bit systems.
LoadModule directive as described in Section 14.1.5.1, “Common httpd.conf Directives”. Note that modules provided by a separate package often have their own configuration file in the /etc/httpd/conf.d/ directory.
LoadModule ssl_module modules/mod_ssl.so
httpd service.
~]# yum install httpd-develapxs) utility required to compile a module.
~]# apxs -i -a -c module_name.c/etc/httpd/conf/httpd.conf as an example, remove the hash sign (that is, #) from the beginning of each line, and customize the options according to your requirements as shown in Example 14.80, “Sample virtual host configuration”.
NameVirtualHost penguin.example.com:80
<VirtualHost penguin.example.com:80>
ServerAdmin webmaster@penguin.example.com
DocumentRoot /www/docs/penguin.example.com
ServerName penguin.example.com:80
ErrorLog logs/penguin.example.com-error_log
CustomLog logs/penguin.example.com-access_log common
</VirtualHost>ServerName must be a valid DNS name assigned to the machine. The <VirtualHost> container is highly customizable, and accepts most of the directives available within the main server configuration. Directives that are not supported within this container include User and Group, which were replaced by SuexecUserGroup.
Listen directive in the global settings section of the /etc/httpd/conf/httpd.conf file accordingly.
httpd service.
mod_ssl, a module that uses the OpenSSL toolkit to provide the SSL/TLS support, is commonly referred to as the SSL server.
mod_ssl prevents any inspection or modification of the transmitted content. This section provides basic information on how to enable this module in the Apache HTTP Server configuration, and guides you through the process of generating private keys and self-signed certificates.
| Web Browser | Link |
|---|---|
| Mozilla Firefox | Mozilla root CA list. |
| Opera | The Opera Rootstore. |
| Internet Explorer | Windows root certificate program members. |
mod_ssl module) and openssl (the OpenSSL toolkit) packages installed. To do so, type the following at a shell prompt:
~]# yum install mod_ssl opensslmod_ssl configuration file at /etc/httpd/conf.d/ssl.conf, which is included in the main Apache HTTP Server configuration file by default. For the module to be loaded, restart the httpd service as described in Section 14.1.4.3, “Restarting the Service”.
/etc/pki/tls/private/ and /etc/pki/tls/certs/ directories respectively. You can do so by typing the following commands:
~]#mvkey_file.key/etc/pki/tls/private/~]#hostname.keymvcertificate.crt/etc/pki/tls/certs/hostname.crt
/etc/httpd/conf.d/ssl.conf configuration file:
SSLCertificateFile /etc/pki/tls/certs/hostname.crt SSLCertificateKeyFile /etc/pki/tls/private/hostname.key
httpd service as described in Section 14.1.4.3, “Restarting the Service”.
~]#mv /etc/httpd/conf/httpsd.key /etc/pki/tls/private/penguin.example.com.key~]#mv /etc/httpd/conf/httpsd.crt /etc/pki/tls/certs/penguin.example.com.crt
~]# yum install crypto-utils~]# openssl req -x509 -new -set_serial number -key hostname.key -out hostname.crt~]# rm /etc/pki/tls/private/hostname.keygenkey command followed by the appropriate hostname (for example, penguin.example.com):
~]#genkeyhostname
1024 bits.
[*]) or disable ([ ]) the encryption of the private key.
/etc/httpd/conf.d/ssl.conf configuration file:
SSLCertificateFile /etc/pki/tls/certs/hostname.crt SSLCertificateKeyFile /etc/pki/tls/private/hostname.key
httpd service as described in Section 14.1.4.3, “Restarting the Service”, so that the updated configuration is loaded.
man httpdhttpd service containing the complete list of its command line options.
man genkeygenkey containing the full documentation on its usage.
dovecot package is installed on your system by running, as root:
~]# yum install dovecotPOP server, email messages are downloaded by email client applications. By default, most POP email clients are automatically configured to delete the message on the email server after it has been successfully transferred, however this setting usually can be changed.
POP is fully compatible with important Internet messaging standards, such as Multipurpose Internet Mail Extensions (MIME), which allow for email attachments.
POP works best for users who have one system on which to read email. It also works well for users who do not have a persistent connection to the Internet or the network containing the mail server. Unfortunately for those with slow network connections, POP requires client programs upon authentication to download the entire content of each message. This can take a long time if any messages have large attachments.
POP protocol is POP3.
POP protocol variants:
POP3 with MDS (Monash Directory Service) authentication. An encoded hash of the user's password is sent from the email client to the server rather then sending an unencrypted password.
POP3 with Kerberos authentication.
POP3 with RPOP authentication. This uses a per-user ID, similar to a password, to authenticate POP requests. However, this ID is not encrypted, so RPOP is no more secure than standard POP.
pop3s service, or by using the /usr/sbin/stunnel application. For more information on securing email communication, refer to Section 15.5.1, “Securing Communication”.
IMAP server under Red Hat Enterprise Linux is Dovecot and is provided by the dovecot package. Refer to Section 15.1.2.1, “POP” for information on how to install Dovecot.
IMAP mail server, email messages remain on the server where users can read or delete them. IMAP also allows client applications to create, rename, or delete mail directories on the server to organize and store email.
IMAP is particularly useful for users who access their email using multiple machines. The protocol is also convenient for users connecting to the mail server via a slow connection, because only the email header information is downloaded for messages until opened, saving bandwidth. The user also has the ability to delete messages without viewing or downloading them.
IMAP client applications are capable of caching copies of messages locally, so the user can browse previously read messages when not directly connected to the IMAP server.
IMAP, like POP, is fully compatible with important Internet messaging standards, such as MIME, which allow for email attachments.
SSL encryption for client authentication and data transfer sessions. This can be enabled by using the imaps service, or by using the /usr/sbin/stunnel program. For more information on securing email communication, refer to Section 15.5.1, “Securing Communication”.
imap-login and pop3-login processes which implement the IMAP and POP3 protocols are spawned by the master dovecot daemon included in the dovecot package. The use of IMAP and POP is configured through the /etc/dovecot/dovecot.conf configuration file; by default dovecot runs IMAP and POP3 together with their secure versions using SSL. To configure dovecot to use POP, complete the following steps:
/etc/dovecot/dovecot.conf configuration file to make sure the protocols variable is uncommented (remove the hash sign (#) at the beginning of the line) and contains the pop3 argument. For example:
protocols = imap imaps pop3 pop3s
protocols variable is left commented out, dovecot will use the default values specified for this variable.
~]# service dovecot restart~]# chkconfig dovecot ondovecot only reports that it started the IMAP server, but also starts the POP3 server.
SMTP, both IMAP and POP3 require connecting clients to authenticate using a username and password. By default, passwords for both protocols are passed over the network unencrypted.
SSL on dovecot:
/etc/pki/dovecot/dovecot-openssl.conf configuration file as you prefer. However, in a typical installation, this file does not require modification.
/etc/pki/dovecot/certs/dovecot.pem and /etc/pki/dovecot/private/dovecot.pem.
/usr/libexec/dovecot/mkcert.sh script which creates the dovecot self signed certificates. These certificates are copied in the /etc/pki/dovecot/certs and /etc/pki/dovecot/private directories. To implement the changes, restart dovecot:
~]# service dovecot restartdovecot can be found online at http://www.dovecot.org.
SMTP. A message may involve several MTAs as it moves to its intended destination.
mail or Procmail.
POP or IMAP protocols, setting up mailboxes to store messages, and sending outbound messages to an MTA.
~]# alternatives --config mta~]# chkconfig <service> <on/off>/usr/sbin/postfix. This daemon launches all related processes needed to handle mail delivery.
/etc/postfix/ directory. The following is a list of the more commonly used files:
access — Used for access control, this file specifies which hosts are allowed to connect to Postfix.
main.cf — The global Postfix configuration file. The majority of configuration options are specified in this file.
master.cf — Specifies how Postfix interacts with various processes to accomplish mail delivery.
transport — Maps email addresses to relay hosts.
aliases file can be found in the /etc/ directory. This file is shared between Postfix and Sendmail. It is a configurable list required by the mail protocol that describes user ID aliases.
/etc/postfix/main.cf file does not allow Postfix to accept network connections from a host other than the local computer. For instructions on configuring Postfix as a server for other clients, refer to Section 15.3.1.2, “Basic Postfix Configuration”.
postfix service after changing any options in the configuration files under the /etc/postfix directory in order for those changes to take effect:
~]# service postfix restart
/etc/postfix/main.cf file with a text editor, such as vi.
mydomain line by removing the hash sign (#), and replace domain.tld with the domain the mail server is servicing, such as example.com.
myorigin = $mydomain line.
myhostname line, and replace host.domain.tld with the hostname for the machine.
mydestination = $myhostname, localhost.$mydomain line.
mynetworks line, and replace 168.100.189.0/28 with a valid network setting for hosts that can connect to the server.
inet_interfaces = all line.
inet_interfaces = localhost line.
postfix service.
/etc/postfix/main.cf configuration file. Additional resources including information about Postfix configuration, SpamAssassin integration, or detailed descriptions of the /etc/postfix/main.cf parameters are available online at http://www.postfix.org/.
LDAP directory as a source for various lookup tables (e.g.: aliases, virtual, canonical, etc.). This allows LDAP to store hierarchical user information and Postfix to only be given the result of LDAP queries when needed. By not storing this information locally, administrators can easily maintain it.
LDAP to look up the /etc/aliases file. Make sure your /etc/postfix/main.cf contains the following:
alias_maps = hash:/etc/aliases, ldap:/etc/postfix/ldap-aliases.cf
/etc/postfix/ldap-aliases.cf file if you do not have one created already and make sure it contains the following:
server_host =ldap.example.comsearch_base = dc=example, dc=com
ldap.example.com, example, and com are parameters that need to be replaced with specification of an existing available LDAP server.
/etc/postfix/ldap-aliases.cf file can specify various parameters, including parameters that enable LDAP SSL and STARTTLS. For more information, refer to the ldap_table(5) man page.
LDAP, refer to Section 16.1, “OpenLDAP”.
SMTP protocol. However, Sendmail is highly configurable, allowing control over almost every aspect of how email is handled, including the protocol used. Many system administrators elect to use Sendmail as their MTA due to its power and scalability.
POP or IMAP, to download their messages to their local machine. Or, they may prefer a Web interface to gain access to their mailbox. These other applications can work in conjunction with Sendmail, but they actually exist for different reasons and can operate separately from one another.
~]# yum install sendmail~]# yum install sendmail-cf/usr/sbin/sendmail.
/etc/mail/sendmail.cf. Avoid editing the sendmail.cf file directly. To make configuration changes to Sendmail, edit the /etc/mail/sendmail.mc file, back up the original /etc/mail/sendmail.cf, and use the following alternatives to generate a new configuration file:
/etc/mail/ (~]# make all -C /etc/mail/) to create a new /etc/mail/sendmail.cf configuration file. All other generated files in /etc/mail (db files) will be regenerated if needed. The old makemap commands are still usable. The make command will automatically be used by service sendmail start | restart | reload.
m4 macro processor to create a new /etc/mail/sendmail.cf. The m4 macro processor is not installed by default. Before using it to create /etc/mail/sendmail.cf, install the m4 package as root:
~]# yum install m4/etc/mail/ directory including:
access — Specifies which systems can use Sendmail for outbound email.
domaintable — Specifies domain name mapping.
local-host-names — Specifies aliases for the host.
mailertable — Specifies instructions that override routing for particular domains.
virtusertable — Specifies a domain-specific form of aliasing, allowing multiple virtual domains to be hosted on one machine.
/etc/mail/, such as access, domaintable, mailertable and virtusertable, must actually store their information in database files before Sendmail can use any configuration changes. To include any changes made to these configurations in their database files, run the following command, as root:
~]# makemap hash /etc/mail/<name> < /etc/mail/<name><name> represents the name of the configuration file to be updated. You may also restart the sendmail service for the changes to take effect by running:
~]# service sendmail restartexample.com domain delivered to bob@other-example.com, add the following line to the virtusertable file:
@example.com bob@other-example.comvirtusertable.db file must be updated:
~]# makemap hash /etc/mail/virtusertable < /etc/mail/virtusertablevirtusertable.db file containing the new configuration.
/etc/mail/sendmail.cf file.
sendmail.cf file, it is a good idea to create a backup copy.
/etc/mail/sendmail.mc file as root. Once you are finished, restart the sendmail service and, if the m4 package is installed, the m4 macro processor will automatically generate a new sendmail.cf configuration file:
~]# service sendmail restartsendmail.cf file does not allow Sendmail to accept network connections from any host other than the local computer. To configure Sendmail as a server for other clients, edit the /etc/mail/sendmail.mc file, and either change the address specified in the Addr= option of the DAEMON_OPTIONS directive from 127.0.0.1 to the IP address of an active network device or comment out the DAEMON_OPTIONS directive all together by placing dnl at the beginning of the line. When finished, regenerate /etc/mail/sendmail.cf by restarting the service
~]# service sendmail restartSMTP-only sites. However, it does not work for UUCP (UNIX-to-UNIX Copy Protocol) sites. If using UUCP mail transfers, the /etc/mail/sendmail.mc file must be reconfigured and a new /etc/mail/sendmail.cf file must be generated.
/usr/share/sendmail-cf/README file before editing any files in the directories under the /usr/share/sendmail-cf directory, as they can affect the future configuration of the /etc/mail/sendmail.cf file.
mail.example.com that handles all of their email and assigns a consistent return address to all outgoing mail.
user@example.com instead of user@host.example.com.
/etc/mail/sendmail.mc:
FEATURE(always_add_domain)dnl FEATURE(`masquerade_entire_domain')dnl FEATURE(`masquerade_envelope')dnl FEATURE(`allmasquerade')dnl MASQUERADE_AS(`bigcorp.com.')dnl MASQUERADE_DOMAIN(`bigcorp.com.')dnl MASQUERADE_AS(bigcorp.com)dnl
sendmail.cf using the m4 macro processor, this configuration makes all mail from inside the network appear as if it were sent from bigcorp.com.
SMTP messages, also called relaying, has been disabled by default since Sendmail version 8.9. Before this change occurred, Sendmail directed the mail host (x.edu) to accept messages from one party (y.com) and sent them to a different party (z.net). Now, however, Sendmail must be configured to permit any domain to relay mail through the server. To configure relay domains, edit the /etc/mail/relay-domains file and restart Sendmail
~]# service sendmail restart/etc/mail/access file can be used to prevent connections from unwanted hosts. The following example illustrates how this file can be used to both block and specifically allow access to the Sendmail server:
badspammer.com ERROR:550 "Go away and do not spam us anymore" tux.badspammer.com OK 10.0 RELAYbadspammer.com is blocked with a 550 RFC-821 compliant error code, with a message sent back to the spammer. Email sent from the tux.badspammer.com sub-domain, is accepted. The last line shows that any email sent from the 10.0.*.* network can be relayed through the mail server.
/etc/mail/access.db file is a database, use the makemap command to update any changes. Do this using the following command as root:
~]# makemap hash /etc/mail/access < /etc/mail/accessSMTP servers store information about an email's journey in the message header. As the message travels from one MTA to another, each puts in a Received header above all the other Received headers. It is important to note that this information may be altered by spammers.
/usr/share/sendmail-cf/README for more information and examples.
LDAP is a very quick and powerful way to find specific information about a particular user from a much larger group. For example, an LDAP server can be used to look up a particular email address from a common corporate directory by the user's last name. In this kind of implementation, LDAP is largely separate from Sendmail, with LDAP storing the hierarchical user information and Sendmail only being given the result of LDAP queries in pre-addressed email messages.
LDAP, where it uses LDAP to replace separately maintained files, such as /etc/aliases and /etc/mail/virtusertables, on different mail servers that work together to support a medium- to enterprise-level organization. In short, LDAP abstracts the mail routing level from Sendmail and its separate configuration files to a powerful LDAP cluster that can be leveraged by many different applications.
LDAP. To extend the Sendmail server using LDAP, first get an LDAP server, such as OpenLDAP, running and properly configured. Then edit the /etc/mail/sendmail.mc to include the following:
LDAPROUTE_DOMAIN('yourdomain.com')dnl
FEATURE('ldap_routing')dnl
LDAP. The configuration can differ greatly from this depending on the implementation of LDAP, especially when configuring several Sendmail machines to use a common LDAP server.
/usr/share/sendmail-cf/README for detailed LDAP routing configuration instructions and examples.
/etc/mail/sendmail.cf file by running the m4 macro processor and again restarting Sendmail. Refer to Section 15.3.2.3, “Common Sendmail Configuration Changes” for instructions.
LDAP, refer to Section 16.1, “OpenLDAP”.
POP3 and IMAP. It can even forward email messages to an SMTP server, if necessary.
~]# yum install fetchmail.fetchmailrc file in the user's home directory. If it does not already exist, create the .fetchmailrc file in your home directory
.fetchmailrc file, Fetchmail checks for email on a remote server and downloads it. It then delivers it to port 25 on the local machine, using the local MTA to place the email in the correct user's spool file. If Procmail is available, it is launched to filter the email and place it in a mailbox so that it can be read by an MUA.
.fetchmailrc file is much easier. Place any desired configuration options in the .fetchmailrc file for those options to be used each time the fetchmail command is issued. It is possible to override these at the time Fetchmail is run by specifying that option on the command line.
.fetchmailrc file contains three classes of configuration options:
.fetchmailrc file, followed by one or more server options, each of which designate a different email server that Fetchmail should check. User options follow server options for each user account checking that email server. Like server options, multiple user options may be specified for use with a particular server as well as to check multiple email accounts on the same server.
.fetchmailrc file by the use of a special option verb, poll or skip, that precedes any of the server information. The poll action tells Fetchmail to use this server option when it is run, which checks for email using the specified user options. Any server options after a skip action, however, are not checked unless this server's hostname is specified when Fetchmail is invoked. The skip option is useful when testing configurations in the .fetchmailrc file because it only checks skipped servers when specifically invoked, and does not affect any currently working configurations.
.fetchmailrc file:
set postmaster "user1"
set bouncemail
poll pop.domain.com proto pop3
user 'user1' there with password 'secret' is user1 here
poll mail.domain2.com
user 'user5' there with password 'secret2' is user1 here
user 'user7' there with password 'secret3' is user1 herepostmaster option) and all email errors are sent to the postmaster instead of the sender (bouncemail option). The set action tells Fetchmail that this line contains a global option. Then, two email servers are specified, one set to check using POP3, the other for trying various protocols to find one that works. Two users are checked using the second server option, but all email found for any user is sent to user1's mail spool. This allows multiple mailboxes to be checked on multiple servers, while appearing in a single MUA inbox. Each user's specific information begins with the user action.
.fetchmailrc file. Omitting the with password '<password>' section causes Fetchmail to ask for a password when it is launched.
fetchmail man page explains each option in detail, but the most common ones are listed in the following three sections.
set action.
daemon <seconds> — Specifies daemon-mode, where Fetchmail stays in the background. Replace <seconds> with the number of seconds Fetchmail is to wait before polling the server.
postmaster — Specifies a local user to send mail to in case of delivery problems.
syslog — Specifies the log file for errors and status messages. By default, this is /var/log/maillog.
.fetchmailrc after a poll or skip action.
auth <auth-type> — Replace <auth-type> with the type of authentication to be used. By default, password authentication is used, but some protocols support other types of authentication, including kerberos_v5, kerberos_v4, and ssh. If the any authentication type is used, Fetchmail first tries methods that do not require a password, then methods that mask the password, and finally attempts to send the password unencrypted to authenticate to the server.
interval <number> — Polls the specified server every <number> port <port-number> — Replace <port-number> with the port number. This value overrides the default port number for the specified protocol.
proto <protocol> — Replace <protocol> with the protocol, such as pop3 or imap, to use when checking for messages on the server.
timeout <seconds> — Replace <seconds> with the number of seconds of server inactivity after which Fetchmail gives up on a connection attempt. If this value is not set, a default of 300 seconds is assumed.
user option (defined below).
fetchall — Orders Fetchmail to download all messages in the queue, including messages that have already been viewed. By default, Fetchmail only pulls down new messages.
fetchlimit <number> — Replace <number> with the number of messages to be retrieved before stopping.
flush — Deletes all previously viewed messages in the queue before retrieving new messages.
limit <max-number-bytes> — Replace <max-number-bytes> with the maximum size in bytes that messages are allowed to be when retrieved by Fetchmail. This option is useful with slow network links, when a large message takes too long to download.
password '<password>' — Replace <password> with the user's password.
preconnect "<command>" — Replace <command> with a command to be executed before retrieving messages for the user.
postconnect "<command>" — Replace <command> with a command to be executed after retrieving messages for the user.
ssl — Activates SSL encryption.
user "<username>" — Replace <username> with the username used by Fetchmail to retrieve messages. This option must precede all other user options.
fetchmail command mirror the .fetchmailrc configuration options. In this way, Fetchmail may be used with or without a configuration file. These options are not used on the command line by most users because it is easier to leave them in the .fetchmailrc file.
fetchmail command with other options for a particular purpose. It is possible to issue command options to temporarily override a .fetchmailrc setting that is causing an error, as any options specified at the command line override configuration file options.
fetchmail command can supply important information.
--configdump — Displays every possible option based on information from .fetchmailrc and Fetchmail defaults. No email is retrieved for any users when using this option.
-s — Executes Fetchmail in silent mode, preventing any messages, other than errors, from appearing after the fetchmail command.
-v — Executes Fetchmail in verbose mode, displaying every communication between Fetchmail and remote email servers.
-V — Displays detailed version information, lists its global options, and shows settings to be used with each user, including the email protocol and authentication method. No email is retrieved for any users when using this option.
.fetchmailrc file.
-a — Fetchmail downloads all messages from the remote email server, whether new or previously viewed. By default, Fetchmail only downloads new messages.
-k — Fetchmail leaves the messages on the remote email server after downloading them. This option overrides the default behavior of deleting messages after downloading them.
-l <max-number-bytes> — Fetchmail does not download any messages over a particular size and leaves them on the remote email server.
--quit — Quits the Fetchmail daemon process.
.fetchmailrc options can be found in the fetchmail man page.
/bin/mail command to send email containing log messages to the root user of the local system.
mail. Both of the applications are considered LDAs and both move email from the MTA's spool file into the user's mailbox. However, Procmail provides a robust filtering system.
mail command, consult its man page (man mail).
/etc/procmailrc or of a ~/.procmailrc file (also called an rc file) in the user's home directory invokes Procmail whenever an MTA receives a new message.
rc files exist in the /etc/ directory and no .procmailrc files exist in any user's home directory. Therefore, to use Procmail, each user must construct a .procmailrc file with specific environment variables and rules.
rc file. If a message matches a recipe, then the email is placed in a specified file, is deleted, or is otherwise processed.
/etc/procmailrc file and rc files in the /etc/procmailrcs directory for default, system-wide, Procmail environmental variables and recipes. Procmail then searches for a .procmailrc file in the user's home directory. Many users also create additional rc files for Procmail that are referred to within the .procmailrc file in their home directory.
~/.procmailrc file in the following format:
<env-variable>="<value>"
<env-variable> <value> DEFAULT — Sets the default mailbox where messages that do not match any recipes are placed.
DEFAULT value is the same as $ORGMAIL.
INCLUDERC — Specifies additional rc files containing more recipes for messages to be checked against. This breaks up the Procmail recipe lists into individual files that fulfill different roles, such as blocking spam and managing email lists, that can then be turned off or on by using comment characters in the user's ~/.procmailrc file.
.procmailrc file may look like this:
MAILDIR=$HOME/Msgs INCLUDERC=$MAILDIR/lists.rc INCLUDERC=$MAILDIR/spam.rc
INCLUDERC line with a hash sign (#).
LOCKSLEEP — Sets the amount of time, in seconds, between attempts by Procmail to use a particular lockfile. The default is 8 seconds.
LOCKTIMEOUT — Sets the amount of time, in seconds, that must pass after a lockfile was last modified before Procmail assumes that the lockfile is old and can be deleted. The default is 1024 seconds.
LOGFILE — The file to which any Procmail information or error messages are written.
MAILDIR — Sets the current working directory for Procmail. If set, all other Procmail paths are relative to this directory.
ORGMAIL — Specifies the original mailbox, or another place to put the messages if they cannot be placed in the default or recipe-required location.
/var/spool/mail/$LOGNAME is used.
SUSPEND — Sets the amount of time, in seconds, that Procmail pauses if a necessary resource, such as swap space, is not available.
SWITCHRC — Allows a user to specify an external file containing additional Procmail recipes, much like the INCLUDERC option, except that recipe checking is actually stopped on the referring configuration file and only the recipes on the SWITCHRC-specified file are used.
VERBOSE — Causes Procmail to log more information. This option is useful for debugging.
LOGNAME, which is the login name; HOME, which is the location of the home directory; and SHELL, which is the default shell.
procmailrc man page.
:0<flags>: <lockfile-name>*<special-condition-character><condition-1>*<special-condition-character><condition-2>*<special-condition-character><condition-N><special-action-character><action-to-perform>
<flags> <lockfile-name>*) can further control the condition.
<action-to-perform>{ }, that are performed on messages which match the recipe's conditions. Nesting blocks can be nested inside one another, providing greater control for identifying and performing actions on messages.
A — Specifies that this recipe is only used if the previous recipe without an A or a flag also matched this message.
a — Specifies that this recipe is only used if the previous recipe with an A or a flag also matched this message and was successfully completed.
B — Parses the body of the message and looks for matching conditions.
b — Uses the body in any resulting action, such as writing the message to a file or forwarding it. This is the default behavior.
c — Generates a carbon copy of the email. This is useful with delivering recipes, since the required action can be performed on the message and a copy of the message can continue being processed in the rc files.
D — Makes the egrep comparison case-sensitive. By default, the comparison process is not case-sensitive.
E — While similar to the A flag, the conditions in the recipe are only compared to the message if the immediately preceding recipe without an E flag did not match. This is comparable to an else action.
e — The recipe is compared to the message only if the action specified in the immediately preceding recipe fails.
f — Uses the pipe as a filter.
H — Parses the header of the message and looks for matching conditions. This is the default behavior.
h — Uses the header in a resulting action. This is the default behavior.
w — Tells Procmail to wait for the specified filter or program to finish, and reports whether or not it was successful before considering the message filtered.
W — Is identical to w except that "Program failure" messages are suppressed.
procmailrc man page.
:) after any flags on a recipe's first line. This creates a local lockfile based on the destination file name plus whatever has been set in the LOCKEXT global environment variable.
*) at the beginning of a recipe's condition line:
! — In the condition line, this character inverts the condition, causing a match to occur only if the condition does not match the message.
< — Checks if the message is under a specified number of bytes.
> — Checks if the message is over a specified number of bytes.
! — In the action line, this character tells Procmail to forward the message to the specified email addresses.
$ — Refers to a variable set earlier in the rc file. This is often used to set a common mailbox that is referred to by various recipes.
| — Starts a specified program to process the message.
{ and } — Constructs a nesting block, used to contain additional recipes to apply to matching messages.
grep man page.
:0: new-mail.spool
LOCKEXT environment variable. No condition is specified, so every message matches this recipe and is placed in the single spool file called new-mail.spool, located within the directory specified by the MAILDIR environment variable. An MUA can then view messages in this file.
rc files to direct messages to a default location.
:0 * ^From: spammer@domain.com /dev/null
spammer@domain.com are sent to the /dev/null device, deleting them.
/dev/null for permanent deletion. If a recipe inadvertently catches unintended messages, and those messages disappear, it becomes difficult to troubleshoot the rule.
/dev/null.
:0: * ^(From|Cc|To).*tux-lug tuxlug
tux-lug@domain.com mailing list are placed in the tuxlug mailbox automatically for the MUA. Note that the condition in this example matches the message if it has the mailing list's email address on the From, Cc, or To lines.
~]# yum install spamassassin~/.procmailrc file:
INCLUDERC=/etc/mail/spamassassin/spamassassin-default.rc/etc/mail/spamassassin/spamassassin-default.rc contains a simple Procmail rule that activates SpamAssassin for all incoming email. If an email is determined to be spam, it is tagged in the header as such and the title is prepended with the following pattern:
*****SPAM*****
:0 Hw * ^X-Spam-Status: Yes spamspam.
spamd) and the client application (spamc). Configuring SpamAssassin this way, however, requires root access to the host.
spamd daemon, type the following command:
~]# service spamassassin startsystem-config-services), to turn on the spamassassin service. Refer to Chapter 9, Services and Daemons for more information about starting and stopping services.
~/.procmailrc file. For a system-wide configuration, place it in /etc/procmailrc:
INCLUDERC=/etc/mail/spamassassin/spamassassin-spamc.rcmutt.
mutt offer SSL-encrypted email sessions.
POP and IMAP protocols pass authentication information unencrypted, it is possible for an attacker to gain access to user accounts by collecting usernames and passwords as they are passed over the network.
IMAP and POP have known port numbers (993 and 995, respectively) that the MUA uses to authenticate and download messages.
IMAP and POP users on the email server is a simple matter.
IMAP or POP, change to the /etc/pki/dovecot/ directory, edit the certificate parameters in the /etc/pki/dovecot/dovecot-openssl.conf configuration file as you prefer, and type the following commands, as root:
dovecot]#rm -f certs/dovecot.pem private/dovecot.pemdovecot]#/usr/libexec/dovecot/mkcert.sh
/etc/dovecot/conf.d/10-ssl.conf file:
ssl_cert = </etc/pki/dovecot/certs/dovecot.pem ssl_key = </etc/pki/dovecot/private/dovecot.pem
service dovecot restart command to restart the dovecot daemon.
stunnel command can be used as an SSL encryption wrapper around the standard, non-secure connections to IMAP or POP services.
stunnel utility uses external OpenSSL libraries included with Red Hat Enterprise Linux to provide strong cryptography and to protect the network connections. It is recommended to apply to a CA to obtain an SSL certificate, but it is also possible to create a self-signed certificate.
stunnel, first ensure the stunnel package is installed on your system by running, as root:
~]# yum install stunnel/etc/pki/tls/certs/ directory, and type the following command:
certs]# make stunnel.pemstunnel configuration file, for example /etc/stunnel/mail.conf, with the following content:
cert = /etc/pki/tls/certs/stunnel.pem [pop3s] accept = 995 connect = 110 [imaps] accept = 993 connect = 143
stunnel with the created configuration file using the /usr/bin/stunnel /etc/stunnel/mail.conf command, it will be possible to use an IMAP or a POP email client and connect to the email server using SSL encryption.
stunnel, refer to the stunnel man page or the documents in the /usr/share/doc/stunnel-<version-number> / directory, where <version-number> is the version number of stunnel.
sendmail and sendmail-cf packages.
/usr/share/sendmail-cf/README — Contains information on the m4 macro processor, file locations for Sendmail, supported mailers, how to access enhanced features, and more.
sendmail and aliases man pages contain helpful information covering various Sendmail options and the proper configuration of the Sendmail /etc/mail/aliases file.
/usr/share/doc/postfix-<version-number> — Contains a large amount of information about ways to configure Postfix. Replace <version-number> with the version number of Postfix.
/usr/share/doc/fetchmail-<version-number> — Contains a full list of Fetchmail features in the FEATURES file and an introductory FAQ document. Replace <version-number> with the version number of Fetchmail.
/usr/share/doc/procmail-<version-number> — Contains a README file that provides an overview of Procmail, a FEATURES file that explores every program feature, and an FAQ file with answers to many common configuration questions. Replace <version-number> with the version number of Procmail.
procmail — Provides an overview of how Procmail works and the steps involved with filtering email.
procmailrc — Explains the rc file format used to construct recipes.
procmailex — Gives a number of useful, real-world examples of Procmail recipes.
procmailsc — Explains the weighted scoring technique used by Procmail to match a particular recipe to a message.
/usr/share/doc/spamassassin-<version-number>/ — Contains a large amount of information pertaining to SpamAssassin. Replace <version-number> with the version number of the spamassassin package.
.procmailrc files and use Procmail scoring to decide if a particular action should be taken.
LDAP (Lightweight Directory Access Protocol) is a set of open protocols used to access centrally stored information over a network. It is based on the X.500 standard for directory sharing, but is less complex and resource-intensive. For this reason, LDAP is sometimes referred to as “X.500 Lite”.
objectClass definition, and can be found in schema files located in the /etc/openldap/slapd.d/cn=config/cn=schema/ directory.
[id] dn:distinguished_nameattribute_type:attribute_value…attribute_type:attribute_value… …
id is a number determined by the application that is used to edit the entry. Each entry can contain as many attribute_type and attribute_value pairs as needed, as long as they are all defined in a corresponding schema file. A blank line indicates the end of an entry.
slapd service as described in Section 16.1.4, “Running an OpenLDAP Server”.
ldapadd utility to add entries to the LDAP directory.
ldapsearch utility to verify that the slapd service is accessing the information correctly.
| Package | Description |
|---|---|
| openldap | A package containing the libraries necessary to run the OpenLDAP server and client applications. |
| openldap-clients | A package containing the command line utilities for viewing and modifying directories on an LDAP server. |
| openldap-servers |
A package containing both the services and utilities to configure and run an LDAP server. This includes the Standalone LDAP Daemon, slapd.
|
| openldap-servers-sql | A package containing the SQL support module. |
| compat-openldap | A package containing the OpenLDAP compatibility libraries. |
| Package | Description |
|---|---|
| nss-pam-ldapd |
A package containing nslcd, a local LDAP name service that allows a user to perform local LDAP queries.
|
| mod_authz_ldap |
A package containing
mod_authz_ldap, the LDAP authorization module for the Apache HTTP Server. This module uses the short form of the distinguished name for a subject and the issuer of the client SSL certificate to determine the distinguished name of the user within an LDAP directory. It is also capable of authorizing users based on attributes of that user's LDAP directory entry, determining access to assets based on the user and group privileges of the asset, and denying access for users with expired passwords. Note that the mod_ssl module is required when using the mod_authz_ldap module.
|
yum command in the following form:
yuminstallpackage…
~]# yum install openldap openldap-clients openldap-serversroot) to run this command. For more information on how to install new packages in Red Hat Enterprise Linux, refer to Section 5.2.4, “Installing Packages”.
slapd service:
| Command | Description |
|---|---|
slapacl
| Allows you to check the access to a list of attributes. |
slapadd
| Allows you to add entries from an LDIF file to an LDAP directory. |
slapauth
| Allows you to check a list of IDs for authentication and authorization permissions. |
slapcat
| Allows you to pull entries from an LDAP directory in the default format and save them in an LDIF file. |
slapdn
| Allows you to check a list of Distinguished Names (DNs) based on available schema syntax. |
slapindex
|
Allows you to re-index the slapd directory based on the current content. Run this utility whenever you change indexing options in the configuration file.
|
slappasswd
|
Allows you to create an encrypted user password to be used with the ldapmodify utility, or in the slapd configuration file.
|
slapschema
| Allows you to check the compliance of a database with the corresponding schema. |
slaptest
| Allows you to check the LDAP server configuration. |
root can run slapadd, the slapd service runs as the ldap user. Because of this, the directory server is unable to modify any files created by slapadd. To correct this issue, after running the slapd utility, type the following at a shell prompt:
~]# chown -R ldap:ldap /var/lib/ldapslapd service before using slapadd, slapcat, or slapindex. You can do so by typing the following at a shell prompt:
~]# service slapd stop
Stopping slapd: [ OK ]slapd service, refer to Section 16.1.4, “Running an OpenLDAP Server”.
| Command | Description |
|---|---|
ldapadd
|
Allows you to add entries to an LDAP directory, either from a file, or from standard input. It is a symbolic link to ldapmodify -a.
|
ldapcompare
| Allows you to compare given attribute with an LDAP directory entry. |
ldapdelete
| Allows you to delete entries from an LDAP directory. |
ldapexop
| Allows you to perform extended LDAP operations. |
ldapmodify
| Allows you to modify entries in an LDAP directory, either from a file, or from standard input. |
ldapmodrdn
| Allows you to modify the RDN value of an LDAP directory entry. |
ldappasswd
| Allows you to set or change the password for an LDAP user. |
ldapsearch
| Allows you to search LDAP directory entries. |
ldapurl
| Allows you to compose or decompose LDAP URLs. |
ldapwhoami
|
Allows you to perform a whoami operation on an LDAP server.
|
ldapsearch, each of these utilities is more easily used by referencing a file containing the changes to be made rather than typing a command for each entry to be changed within an LDAP directory. The format of such a file is outlined in the man page for each utility.
/etc/openldap/ directory. The following table highlights the most important directories and files within this directory:
/etc/openldap/slapd.conf file. Instead, it uses a configuration database located in the /etc/openldap/slapd.d/ directory. If you have an existing slapd.conf file from a previous installation, you can convert it to the new format by running the following command:
~]# slaptest -f /etc/openldap/slapd.conf -F /etc/openldap/slapd.d/slapd configuration consists of LDIF entries organized in a hierarchical directory structure, and the recommended way to edit these entries is to use the server utilities described in Section 16.1.2.1, “Overview of OpenLDAP Server Utilities”.
slapd service unable to start. Because of this, it is strongly advised that you avoid editing the LDIF files within the /etc/openldap/slapd.d/ directly.
/etc/openldap/slapd.d/cn=config.ldif file. The following directives are commonly used:
olcAllows olcAllows directive allows you to specify which features to enable. It takes the following form:
olcAllows:feature…
bind_v2.
| Option | Description |
|---|---|
bind_v2
| Enables the acceptance of LDAP version 2 bind requests. |
bind_anon_cred
| Enables an anonymous bind when the Distinguished Name (DN) is empty. |
bind_anon_dn
| Enables an anonymous bind when the Distinguished Name (DN) is not empty. |
update_anon
| Enables processing of anonymous update operations. |
proxy_authz_anon
| Enables processing of anonymous proxy authorization control. |
olcAllows: bind_v2 update_anon
olcConnMaxPending olcConnMaxPending directive allows you to specify the maximum number of pending requests for an anonymous session. It takes the following form:
olcConnMaxPending:number
100.
olcConnMaxPending: 100
olcConnMaxPendingAuth olcConnMaxPendingAuth directive allows you to specify the maximum number of pending requests for an authenticated session. It takes the following form:
olcConnMaxPendingAuth:number
1000.
olcConnMaxPendingAuth: 1000
olcDisallows olcDisallows directive allows you to specify which features to disable. It takes the following form:
olcDisallows:feature…
| Option | Description |
|---|---|
bind_anon
| Disables the acceptance of anonymous bind requests. |
bind_simple
| Disables the simple bind authentication mechanism. |
tls_2_anon
| Disables the enforcing of an anonymous session when the STARTTLS command is received. |
tls_authc
| Disallows the STARTTLS command when authenticated. |
olcDisallows: bind_anon
olcIdleTimeout olcIdleTimeout directive allows you to specify how many seconds to wait before closing an idle connection. It takes the following form:
olcIdleTimeout:number
0).
olcIdleTimeout: 180
olcLogFile olcLogFile directive allows you to specify a file in which to write log messages. It takes the following form:
olcLogFile:file_name
olcLogFile: /var/log/slapd.log
olcReferral olcReferral option allows you to specify a URL of a server to process the request in case the server is not able to handle it. It takes the following form:
olcReferral:URL
olcReferral: ldap://root.openldap.org
olcWriteTimeout olcWriteTimeout option allows you to specify how many seconds to wait before closing a connection with an outstanding write request. It takes the following form:
olcWriteTimeout0).
olcWriteTimeout: 180
/etc/openldap/slapd.d/cn=config/olcDatabase={1}bdb.ldif file. The following directives are commonly used in a database-specific configuration:
olcReadOnly olcReadOnly directive allows you to use the database in a read-only mode. It takes the following form:
olcReadOnly:boolean
TRUE (enable the read-only mode), or FALSE (enable modifications of the database). The default option is FALSE.
olcReadOnly: TRUE
olcRootDN olcRootDN directive allows you to specify the user that is unrestricted by access controls or administrative limit parameters set for operations on the LDAP directory. It takes the following form:
olcRootDN:distinguished_name
cn=Manager,dn=my-domain,dc=com.
olcRootDN: cn=root,dn=example,dn=com
olcRootPW olcRootPW directive allows you to set a password for the user that is specified using the olcRootDN directive. It takes the following form:
olcRootPW:password
~]$ slappaswd
New password:
Re-enter new password:
{SSHA}WczWsyPEnMchFf1GRTweq2q7XJcvmSxDolcRootPW: {SSHA}WczWsyPEnMchFf1GRTweq2q7XJcvmSxDolcSuffix olcSuffix directive allows you to specify the domain for which to provide information. It takes the following form:
olcSuffix:domain_name
dc=my-domain,dc=com.
olcSuffix: dc=example,dc=com
/etc/openldap/slapd.d/ directory also contains LDAP definitions that were previously located in /etc/openldap/schema/. It is possible to extend the schema used by OpenLDAP to support additional attribute types and object classes using the default schema files as a guide. However, this task is beyond the scope of this chapter. For more information on this topic, refer to http://www.openldap.org/doc/admin/schema.html.
slapd service, type the following at a shell prompt:
~]# service slapd start
Starting slapd: [ OK ]~]# chkconfig slapd onslapd service, type the following at a shell prompt:
~]# service slapd stop
Stopping slapd: [ OK ]~]# chkconfig slapd off~]# yum install openldap openldap-clients nss-pam-ldapd~]# yum install migrationtools/usr/share/migrationtools/ directory. Once installed, edit the /usr/share/migrationtools/migrate_common.ph file and change the following lines to reflect the correct domain, for example:
# Default DNS domain $DEFAULT_MAIL_DOMAIN = "example.com"; # Default base $DEFAULT_BASE = "dc=example,dc=com";
migrate_all_online.sh script with the default base set to dc=example,dc=com, type:
~]#export DEFAULT_BASE="dc=example,dc=com" \/usr/share/migrationtools/migrate_all_online.sh
| Existing Name Service | Is LDAP Running? | Script to Use |
|---|---|---|
/etc flat files
| yes |
migrate_all_online.sh
|
/etc flat files
| no |
migrate_all_offline.sh
|
| NetInfo | yes |
migrate_all_netinfo_online.sh
|
| NetInfo | no |
migrate_all_netinfo_offline.sh
|
| NIS (YP) | yes |
migrate_all_nis_online.sh
|
| NIS (YP) | no |
migrate_all_nis_offline.sh
|
README and the migration-tools.txt files in the /usr/share/doc/migrationtools-version/ directory.
/usr/share/doc/openldap-servers-version/guide.html/usr/share/doc/openldap-servers-version/README.schemaman ldapadd — Describes how to add entries to an LDAP directory.
man ldapdelete — Describes how to delete entries within an LDAP directory.
man ldapmodify — Describes how to modify entries within an LDAP directory.
man ldapsearch — Describes how to search for entries within an LDAP directory.
man ldappasswd — Describes how to set or change the password of an LDAP user.
man ldapcompare — Describes how to use the ldapcompare tool.
man ldapwhoami — Describes how to use the ldapwhoami tool.
man ldapmodrdn — Describes how to modify the RDNs of entries.
man slapd — Describes command line options for the LDAP server.
man slapadd — Describes command line options used to add entries to a slapd database.
man slapcat — Describes command line options used to generate an LDIF file from a slapd database.
man slapindex — Describes command line options used to regenerate an index based upon the contents of a slapd database.
man slappasswd — Describes command line options used to generate user passwords for LDAP directories.
man ldap.conf — Describes the format and options available within the configuration file for LDAP clients.
man slapd-config — Describes the format and options available within the configuration directory.
smb.conf FileSMB) protocol. It allows the networking of Microsoft Windows®, Linux, UNIX, and other operating systems together, enabling access to Windows-based file and printer shares. Samba's use of SMB allows it to appear as a Windows server to Windows clients.
~]# yum install sambaLDAP) and Kerberos
WINS) name server resolution
smbd, nmbd, and winbindd). Three services (smb, nmb, and winbind) control how the daemons are started, stopped, and other service-related features. These services act as different init scripts. Each daemon is listed in detail below, as well as which specific service has control over it.
smbdsmbd server daemon provides file sharing and printing services to Windows clients. In addition, it is responsible for user authentication, resource locking, and data sharing through the SMB protocol. The default ports on which the server listens for SMB traffic are TCP ports 139 and 445.
smbd daemon is controlled by the smb service.
nmbdnmbd server daemon understands and replies to NetBIOS name service requests such as those produced by SMB/Common Internet File System (CIFS) in Windows-based systems. These systems include Windows 95/98/ME, Windows NT, Windows 2000, Windows XP, and LanManager clients. It also participates in the browsing protocols that make up the Windows Network Neighborhood view. The default port that the server listens to for NMB traffic is UDP port 137.
nmbd daemon is controlled by the nmb service.
winbinddwinbind service resolves user and group information on a server running Windows NT, 2000, 2003 or Windows Server 2008. This makes Windows user / group information understandable by UNIX platforms. This is achieved by using Microsoft RPC calls, Pluggable Authentication Modules (PAM), and the Name Service Switch (NSS). This allows Windows NT domain users to appear and operate as UNIX users on a UNIX machine. Though bundled with the Samba distribution, the winbind service is controlled separately from the smb service.
winbindd daemon is controlled by the winbind service and does not require the smb service to be started in order to operate. winbindd is also used when Samba is an Active Directory member, and may also be used on a Samba domain controller (to implement nested groups and/or interdomain trust). Because winbind is a client-side service used to connect to Windows NT-based servers, further discussion of winbind is beyond the scope of this chapter.
winbind for authentication, refer to Section 10.1.2.3, “Configuring Winbind Authentication”.
smb: in the → bar of Nautilus to view the workgroups/domains.
SMB workgroup or domain on the network.
<servername> and <sharename> with the appropriate values):
smb://<servername>/<sharename>
~]# mount -t cifs //<servername>/<sharename> /mnt/point/ -o username=<username>,password=<password> <sharename> from <servername> in the local directory /mnt/point/.
~]# yum install cifs-utilsman cifs.upcall.
man mount.cifs.
~]# echo 0x37 > /proc/fs/cifs/SecurityFlags
/etc/samba/smb.conf) allows users to view their home directories as a Samba share. It also shares all printers configured for the system as Samba shared printers. In other words, you can attach a printer to the system and print to it from the Windows machines on your network.
/etc/samba/smb.conf as its configuration file. If you change this configuration file, the changes do not take effect until you restart the Samba daemon with the following command, as root:
~]# service smb restart
/etc/samba/smb.conf file:
workgroup =WORKGROUPNAMEserver string =BRIEF COMMENT ABOUT SERVER
WORKGROUPNAME with the name of the Windows workgroup to which this machine should belong. The BRIEF COMMENT ABOUT SERVER is optional and is used as the Windows comment about the Samba system.
/etc/samba/smb.conf file (after modifying it to reflect your needs and your system):
[sharename] comment =Insert a comment herepath =/home/share/valid users =tfox carolepublic = no writable = yes printable = no create mask = 0765
tfox and carole to read and write to the directory /home/share, on the Samba server, from a Samba client.
~]# service smb startnet join command before starting the smb service.
~]# service smb stoprestart option is a quick way of stopping and then starting Samba. This is the most reliable way to make configuration changes take effect after editing the configuration file for Samba. Note that the restart option starts the daemon even if it was not running originally.
~]# service smb restartcondrestart (conditional restart) option only starts smb on the condition that it is currently running. This option is useful for scripts, because it does not start the daemon if it is not running.
/etc/samba/smb.conf file is changed, Samba automatically reloads it after a few minutes. Issuing a manual restart or reload is just as effective.
~]# service smb condrestart/etc/samba/smb.conf file can be useful in case of a failed automatic reload by the smb service. To ensure that the Samba server configuration file is reloaded without restarting the service, type the following command, as root:
~]# service smb reloadsmb service does not start automatically at boot time. To configure Samba to start at boot time, use an initscript utility, such as /sbin/chkconfig, /usr/sbin/ntsysv, or the Services Configuration Tool program. Refer to Chapter 9, Services and Daemons for more information regarding these tools.
smb.conf File/etc/samba/smb.conf configuration file. Although the default smb.conf file is well documented, it does not address complex topics such as LDAP, Active Directory, and the numerous domain controller implementations.
/etc/samba/smb.conf file for a successful configuration.
/etc/samba/smb.conf file shows a sample configuration needed to implement anonymous read-only file sharing. The security = share parameter makes a share anonymous. Note, security levels for a single Samba server cannot be mixed. The security directive is a global Samba parameter located in the [global] configuration section of the /etc/samba/smb.conf file.
[global] workgroup = DOCS netbios name = DOCS_SRV security = share [data] comment = Documentation Samba Server path = /export read only = Yes guest only = Yes
/etc/samba/smb.conf file shows a sample configuration needed to implement anonymous read/write file sharing. To enable anonymous read/write file sharing, set the read only directive to no. The force user and force group directives are also added to enforce the ownership of any newly placed files specified in the share.
force user) and group (force group) in the /etc/samba/smb.conf file.
[global] workgroup = DOCS netbios name = DOCS_SRV security = share [data] comment = Data path = /export force user = docsbot force group = users read only = No guest ok = Yes
/etc/samba/smb.conf file shows a sample configuration needed to implement an anonymous print server. Setting browseable to no as shown does not list the printer in Windows Network Neighborhood. Although hidden from browsing, configuring the printer explicitly is possible. By connecting to DOCS_SRV using NetBIOS, the client can have access to the printer if the client is also part of the DOCS workgroup. It is also assumed that the client has the correct local printer driver installed, as the use client driver directive is set to Yes. In this case, the Samba server has no responsibility for sharing printer drivers to the client.
[global] workgroup = DOCS netbios name = DOCS_SRV security = share printcap name = cups disable spools= Yes show add printer wizard = No printing = cups [printers] comment = All Printers path = /var/spool/samba guest ok = Yes printable = Yes use client driver = Yes browseable = Yes
/etc/samba/smb.conf file shows a sample configuration needed to implement a secure read/write print server. Setting the security directive to user forces Samba to authenticate client connections. Notice the [homes] share does not have a force user or force group directive as the [public] share does. The [homes] share uses the authenticated user details for any files created as opposed to the force user and force group in [public].
[global] workgroup = DOCS netbios name = DOCS_SRV security = user printcap name = cups disable spools = Yes show add printer wizard = No printing = cups [homes] comment = Home Directories valid users = %S read only = No browseable = No [public] comment = Data path = /export force user = docsbot force group = users guest ok = Yes [printers] comment = All Printers path = /var/spool/samba printer admin = john, ed, @admins create mask = 0600 guest ok = Yes printable = Yes use client driver = Yes browseable = Yes
/etc/samba/smb.conf file shows a sample configuration needed to implement an Active Directory domain member server. In this example, Samba authenticates users for services being run locally but is also a client of the Active Directory. Ensure that your kerberos realm parameter is shown in all caps (for example realm = EXAMPLE.COM). Since Windows 2000/2003/2008 requires Kerberos for Active Directory authentication, the realm directive is required. If Active Directory and Kerberos are running on different servers, the password server directive may be required to help the distinction.
[global] realm = EXAMPLE.COM security = ADS encrypt passwords = yes # Optional. Use only if Samba cannot determine the Kerberos server automatically. password server = kerberos.example.com
/etc/samba/smb.conf file on the member server
/etc/krb5.conf file, on the member server
kinit administrator@EXAMPLE.COMkinit command is a Kerberos initialization script that references the Active Directory administrator account and Kerberos realm. Since Active Directory requires Kerberos tickets, kinit obtains and caches a Kerberos ticket-granting ticket for client/server authentication. For more information on Kerberos, the /etc/krb5.conf file, and the kinit command, refer to the Using Kerberos section of the Red Hat Enterprise Linux 6 Managing Single Sign-On and Smart Cards guide.
net ads join -S windows1.example.com -U administrator%passwordwindows1 was automatically found in the corresponding Kerberos realm (the kinit command succeeded), the net command connects to the Active Directory server using its required administrator account and password. This creates the appropriate machine account on the Active Directory and grants permissions to the Samba domain member server to join the domain.
security = ads and not security = user is used, a local password back end such as smbpasswd is not needed. Older clients that do not support security = ads are authenticated as if security = domain had been set. This change does not affect functionality and allows local users not previously in the domain.
/etc/samba/smb.conf file shows a sample configuration needed to implement a Windows NT4-based domain member server. Becoming a member server of an NT4-based domain is similar to connecting to an Active Directory. The main difference is NT4-based domains do not use Kerberos in their authentication method, making the /etc/samba/smb.conf file simpler. In this instance, the Samba member server functions as a pass through to the NT4-based domain server.
[global] workgroup = DOCS netbios name = DOCS_SRV security = domain [homes] comment = Home Directories valid users = %S read only = No browseable = No [public] comment = Data path = /export force user = docsbot force group = users guest ok = Yes
/etc/samba/smb.conf file to convert the server to a Samba-based PDC. If Windows NT-based servers are upgraded to Windows 2000/2003/2008, the /etc/samba/smb.conf file is easily modifiable to incorporate the infrastructure change to Active Directory if needed.
/etc/samba/smb.conf file, join the domain before starting Samba by typing the following command as root:
net rpc join -U administrator%password-S option, which specifies the domain server hostname, does not need to be stated in the net rpc join command. Samba uses the hostname specified by the workgroup directive in the /etc/samba/smb.conf file instead of it being stated explicitly.
tdbsamtdbsam password database back end. Replacing the aging smbpasswd back end, tdbsam has numerous improvements that are explained in more detail in Section 17.1.8, “Samba Account Information Databases”. The passdb backend directive controls which back end is to be used for the PDC.
/etc/samba/smb.conf file shows a sample configuration needed to implement a tdbsam password database back end.
[global]
workgroup = DOCS
netbios name = DOCS_SRV
passdb backend = tdbsam
security = user
add user script = /usr/sbin/useradd -m "%u"
delete user script = /usr/sbin/userdel -r "%u"
add group script = /usr/sbin/groupadd "%g"
delete group script = /usr/sbin/groupdel "%g"
add user to group script = /usr/sbin/usermod -G "%g" "%u"
add machine script = /usr/sbin/useradd -s /bin/false -d /dev/null -g machines "%u"
# The following specifies the default logon script
# Per user logon scripts can be specified in the user
# account using pdbedit logon script = logon.bat
# This sets the default profile path.
# Set per user paths with pdbedit
logon drive = H:
domain logons = Yes
os level = 35
preferred master = Yes
domain master = Yes
[homes]
comment = Home Directories
valid users = %S
read only = No
[netlogon]
comment = Network Logon Service
path = /var/lib/samba/netlogon/scripts
browseable = No
read only = No
# For profiles to work, create a user directory under the
# path shown.
mkdir -p /var/lib/samba/profiles/john
[Profiles]
comment = Roaming Profile Share
path = /var/lib/samba/profiles
read only = No
browseable = No
guest ok = Yes
profile acls = Yes
# Other resource shares ... ...
tdbsam follow these steps:
smb.conf file as shown in the example above.
~]# smbpasswd -a root
Provide the password here.
smb service.
~]# groupadd -f users~]# groupadd -f nobody~]# groupadd -f ntadmins
~]# net groupmap add ntgroup="Domain Users" unixgroup=users~]# net groupmap add ntgroup="Domain Guests" unixgroup=nobody~]# net groupmap add ntgroup="Domain Admins" unixgroup=ntadmins
~]# net rpc rights grant 'DOCS\Domain Admins' SetMachineAccountPrivilege -S PDC -U root
tdbsam authentication back end. LDAP is recommended in these cases.
security = user directive is not listed in the /etc/samba/smb.conf file, it is used by Samba. If the server accepts the client's username/password, the client can then mount multiple shares without specifying a password for each instance. Samba can also accept session-based username/password requests. The client maintains multiple authentication contexts by using a unique UID for each logon.
/etc/samba/smb.conf file, the security = user directive that sets user-level security is:
[GLOBAL] ... security = user ...
/etc/samba/smb.conf file:
[GLOBAL] ... security = domain workgroup = MARKETING ...
/etc/samba/smb.conf file, the following directives make Samba an Active Directory member server:
[GLOBAL] ... security = ADS realm = EXAMPLE.COM password server = kerberos.example.com ...
/etc/samba/smb.conf, the following directives enable Samba to operate in server security mode:
[GLOBAL] ... encrypt passwords = Yes security = server password server = "NetBIOS_of_Domain_Controller" ...
/etc/passwd type back ends. With a plain text back end, all usernames and passwords are sent unencrypted between the client and the Samba server. This method is very unsecure and is not recommended for use by any means. It is possible that different Windows clients connecting to the Samba server with plain text passwords cannot support such an authentication method.
smbpasswd smbpasswd back end utilizes a plain ASCII text layout that includes the MS Windows LanMan and NT account, and encrypted password information. The smbpasswd back end lacks the storage of the Windows NT/2000/2003 SAM extended controls. The smbpasswd back end is not recommended because it does not scale well or hold any Windows information, such as RIDs for NT-based groups. The tdbsam back end solves these issues for use in a smaller database (250 users), but is still not an enterprise-class solution.
ldapsam_compat ldapsam_compat back end allows continued OpenLDAP support for use with upgraded versions of Samba. This option is normally used when migrating to Samba 3.0.
tdbsam tdbsam password back end provides an ideal database back end for local servers, servers that do not need built-in database replication, and servers that do not require the scalability or complexity of LDAP. The tdbsam back end includes all of the smbpasswd database information as well as the previously-excluded SAM information. The inclusion of the extended SAM data allows Samba to implement the same account and system access controls as seen with Windows NT/2000/2003/2008-based systems.
tdbsam back end is recommended for 250 users at most. Larger organizations should require Active Directory or LDAP integration due to scalability and possible network infrastructure concerns.
ldapsam ldapsam back end provides an optimal distributed account installation method for Samba. LDAP is optimal because of its ability to replicate its database to any number of servers such as the Red Hat Directory Server or an OpenLDAP Server. LDAP databases are light-weight and scalable, and as such are preferred by large enterprises. Installation and configuration of directory servers is beyond the scope of this chapter. For more information on the Red Hat Directory Server, refer to the Red Hat Directory Server 8.2 Deployment Guide. For more information on LDAP, refer to Section 16.1, “OpenLDAP”.
/usr/share/doc/samba-<version>/LDAP/samba.schema) and the Red Hat Directory Server schema file (/usr/share/doc/samba-<version>/LDAP/samba-schema-FDS.ldif) have changed. These files contain the attribute syntax definitions and objectclass definitions that the ldapsam back end needs in order to function properly.
ldapsam back end for your Samba server, you will need to configure slapd to include one of these schema file. Refer to Section 16.1.3.3, “Extending Schema” for directions on how to do this.
openldap-server package installed if you want to use the ldapsam back end.
TCP/IP. NetBIOS-based networking uses broadcast (UDP) messaging to accomplish browse list management. Without NetBIOS and WINS as the primary method for TCP/IP hostname resolution, other methods such as static files (/etc/hosts) or DNS, must be used.
/etc/samba/smb.conf file for a local master browser (or no browsing at all) in a domain controller environment is the same as workgroup configuration.
/etc/samba/smb.conf file in which the Samba server is serving as a WINS server:
[global] wins support = Yes
smb.conf Settings/etc/samba/smb.conf configuration for CUPS support:
[global] load printers = Yes printing = cups printcap name = cups [printers] comment = All Printers path = /var/spool/samba browseable = No public = Yes guest ok = Yes writable = No printable = Yes printer admin = @ntadmins [print$] comment = Printer Drivers Share path = /var/lib/samba/drivers write list = ed, john printer admin = ed, john
print$ directive contains printer drivers for clients to access if not available locally. The print$ directive is optional and may not be required depending on the organization.
browseable to Yes enables the printer to be viewed in the Windows Network Neighborhood, provided the Samba server is set up correctly in the domain/workgroup.
findsmb program is a Perl script which reports information about SMB-aware systems on a specific subnet. If no subnet is specified the local subnet is used. Items displayed include IP address, NetBIOS name, workgroup or domain name, operating system, and version.
findsmb as any valid user on a system:
~]$ findsmb
IP ADDR NETBIOS NAME WORKGROUP/OS/VERSION
------------------------------------------------------------------
10.1.59.25 VERVE [MYGROUP] [Unix] [Samba 3.0.0-15]
10.1.59.26 STATION22 [MYGROUP] [Unix] [Samba 3.0.2-7.FC1]
10.1.56.45 TREK +[WORKGROUP] [Windows 5.0] [Windows 2000 LAN Manager]
10.1.57.94 PIXEL [MYGROUP] [Unix] [Samba 3.0.0-15]
10.1.57.137 MOBILE001 [WORKGROUP] [Windows 5.0] [Windows 2000 LAN Manager]
10.1.57.141 JAWS +[KWIKIMART] [Unix] [Samba 2.2.7a-security-rollup-fix]
10.1.56.159 FRED +[MYGROUP] [Unix] [Samba 3.0.0-14.3E]
10.1.59.192 LEGION *[MYGROUP] [Unix] [Samba 2.2.7-security-rollup-fix]
10.1.56.205 NANCYN +[MYGROUP] [Unix] [Samba 2.2.7a-security-rollup-fix]
net utility is similar to the net utility used for Windows and MS-DOS. The first argument is used to specify the protocol to use when executing a command. The <protocol> ads, rap, or rpc for specifying the type of server connection. Active Directory uses ads, Win9x/NT3 uses rap, and Windows NT4/2000/2003/2008 uses rpc. If the protocol is omitted, net automatically tries to determine it.
wakko:
~]$ net -l share -S wakko
Password:
Enumerating shared resources (exports) on remote server:
Share name Type Description
---------- ---- -----------
data Disk Wakko data share
tmp Disk Wakko tmp share
IPC$ IPC IPC Service (Samba Server)
ADMIN$ IPC IPC Service (Samba Server)
wakko:
~]$ net -l user -S wakko
root password:
User name Comment
-----------------------------
andriusb Documentation
joe Marketing
lisa Sales
nmblookup program resolves NetBIOS names into IP addresses. The program broadcasts its query on the local subnet until the target machine replies.
~]$ nmblookup trek
querying trek on 10.1.59.255
10.1.56.45 trek<00>
pdbedit program manages accounts located in the SAM database. All back ends are supported including smbpasswd, LDAP, and the tdb database library.
~]$ pdbedit -a kristinnew password: retype new password: Unix username: kristin NT username: Account Flags: [U ] User SID: S-1-5-21-1210235352-3804200048-1474496110-2012 Primary Group SID: S-1-5-21-1210235352-3804200048-1474496110-2077 Full Name: Home Directory: \\wakko\kristin HomeDir Drive: Logon Script: Profile Path: \\wakko\kristin\profile Domain: WAKKO Account desc: Workstations: Munged dial: Logon time: 0 Logoff time: Mon, 18 Jan 2038 22:14:07 GMT Kickoff time: Mon, 18 Jan 2038 22:14:07 GMT Password last set: Thu, 29 Jan 2004 08:29:28 GMT Password can change: Thu, 29 Jan 2004 08:29:28 GMT Password must change: Mon, 18 Jan 2038 22:14:07 GMT~]$ pdbedit -v -L kristinUnix username: kristin NT username: Account Flags: [U ] User SID: S-1-5-21-1210235352-3804200048-1474496110-2012 Primary Group SID: S-1-5-21-1210235352-3804200048-1474496110-2077 Full Name: Home Directory: \\wakko\kristin HomeDir Drive: Logon Script: Profile Path: \\wakko\kristin\profile Domain: WAKKO Account desc: Workstations: Munged dial: Logon time: 0 Logoff time: Mon, 18 Jan 2038 22:14:07 GMT Kickoff time: Mon, 18 Jan 2038 22:14:07 GMT Password last set: Thu, 29 Jan 2004 08:29:28 GMT Password can change: Thu, 29 Jan 2004 08:29:28 GMT Password must change: Mon, 18 Jan 2038 22:14:07 GMT~]$ pdbedit -Landriusb:505: joe:503: lisa:504: kristin:506:~]$ pdbedit -x joe~]$ pdbedit -Landriusb:505: lisa:504: kristin:506:
rpcclient program issues administrative commands using Microsoft RPCs, which provide access to the Windows administration graphical user interfaces (GUIs) for systems management. This is most often used by advanced users that understand the full complexity of Microsoft RPCs.
smbcacls program modifies Windows ACLs on files and directories shared by a Samba server or a Windows server.
smbclient program is a versatile UNIX client which provides functionality similar to ftp.
smbcontrol <options> <destination> <messagetype> <parameters>
smbcontrol program sends control messages to running smbd, nmbd, or winbindd daemons. Executing smbcontrol -i runs commands interactively until a blank line or a 'q' is entered.
smbpasswd program manages encrypted passwords. This program can be run by a superuser to change any user's password as well as by an ordinary user to change their own Samba password.
smbspool program is a CUPS-compatible printing interface to Samba. Although designed for use with CUPS printers, smbspool can work with non-CUPS printers as well.
smbstatus program displays the status of current connections to a Samba server.
smbtar program performs backup and restores of Windows-based share files and directories to a local tape archive. Though similar to the tar command, the two are not compatible.
testparm program checks the syntax of the /etc/samba/smb.conf file. If your /etc/samba/smb.conf file is in the default location (/etc/samba/smb.conf) you do not need to specify the location. Specifying the hostname and IP address to the testparm program verifies that the hosts.allow and host.deny files are configured correctly. The testparm program also displays a summary of your /etc/samba/smb.conf file and the server's role (stand-alone, domain, etc.) after testing. This is convenient when debugging as it excludes comments and concisely presents information for experienced administrators to read.
~]$ testparmLoad smb config files from /etc/samba/smb.conf Processing section "[homes]" Processing section "[printers]" Processing section "[tmp]" Processing section "[html]" Loaded services file OK. Server role: ROLE_STANDALONE Press enter to see a dump of your service definitions<enter># Global parameters [global] workgroup = MYGROUP server string = Samba Server security = SHARE log file = /var/log/samba/%m.log max log size = 50 socket options = TCP_NODELAY SO_RCVBUF=8192 SO_SNDBUF=8192 dns proxy = No [homes] comment = Home Directories read only = No browseable = No [printers] comment = All Printers path = /var/spool/samba printable = Yes browseable = No [tmp] comment = Wakko tmp path = /tmp guest only = Yes [html] comment = Wakko www path = /var/www/html force user = andriusb force group = users read only = No guest only = Yes
wbinfo program displays information from the winbindd daemon. The winbindd daemon must be running for wbinfo to work.
~]# yum install samba-doc/usr/share/doc/samba-<version-number>/ — All additional files included with the Samba distribution. This includes all helper scripts, sample configuration files, and documentation. This directory also contains online versions of The Official Samba-3 HOWTO-Collection and Samba-3 by Example, both of which are cited below.
smb.conf
samba
smbd
nmbd
winbind
FTP) is one of the oldest and most commonly used protocols found on the Internet today. Its purpose is to reliably transfer files between computer hosts on a network without requiring the user to log directly into the remote host or have knowledge of how to use the remote system. It allows users to access files on remote systems using a standard set of simple commands.
FTP protocol, as well as configuration options for the primary FTP server shipped with Red Hat Enterprise Linux, vsftpd.
FTP is so prevalent on the Internet, it is often required to share files to the public. System administrators, therefore, should be aware of the FTP protocol's unique characteristics.
FTP requires multiple network ports to work properly. When an FTP client application initiates a connection to an FTP server, it opens port 21 on the server — known as the command port. This port is used to issue all commands to the server. Any data requested from the server is returned to the client via a data port. The port number for data connections, and the way in which data connections are initialized, vary depending upon whether the client requests the data in active or passive mode.
FTP protocol for transferring data to the client application. When an active mode data transfer is initiated by the FTP client, the server opens a connection from port 20 on the server to the IP address and a random, unprivileged port (greater than 1024) specified by the client. This arrangement means that the client machine must be allowed to accept connections over any port above 1024. With the growth of insecure networks, such as the Internet, the use of firewalls to protect client machines is now prevalent. Because these client-side firewalls often deny incoming connections from active mode FTP servers, passive mode was devised.
FTP client application. When requesting data from the server, the FTP client indicates it wants to access the data in passive mode and the server provides the IP address and a random, unprivileged port (greater than 1024) on the server. The client then connects to that port on the server to download the requested information.
FTP server. This also simplifies the process of configuring firewall rules for the server. Refer to Section 17.2.5.8, “Network Options” for more information about limiting passive ports.
FTP servers:
FTP services. Since speed is its primary design goal, it has limited functionality and runs only as an anonymous FTP server. For more information about configuring and administering Red Hat Content Accelerator, consult the documentation available online at http://www.redhat.com/docs/manuals/tux/.
vsftpd — A fast, secure FTP daemon which is the preferred FTP server for Red Hat Enterprise Linux. The remainder of this section focuses on vsftpd.
vsftpdvsftpd) is designed from the ground up to be fast, stable, and, most importantly, secure. vsftpd is the only stand-alone FTP server distributed with Red Hat Enterprise Linux, due to its ability to handle large numbers of connections efficiently and securely.
vsftpd has three primary aspects:
libcap library, tasks that usually require full root privileges can be executed more safely from a less privileged process.
chroot jail — Whenever possible, processes are change-rooted to the directory being shared; this directory is then considered a chroot jail. For example, if the directory /var/ftp/ is the primary shared directory, vsftpd reassigns /var/ftp/ to the new root directory, known as /. This disallows any potential malicious hacker activities for any directories not contained below the new root directory.
vsftpd deals with requests:
FTP clients and run with as close to no privileges as possible.
HTTP Server, vsftpd launches unprivileged child processes to handle incoming connections. This allows the privileged, parent process to be as small as possible and handle relatively few tasks.
FTP clients is handled by unprivileged child processes in a chroot jail — Because these child processes are unprivileged and only have access to the directory being shared, any crashed processes only allows the attacker access to the shared files.
vsftpdvsftpd RPM installs the daemon (/usr/sbin/vsftpd), its configuration and related files, as well as FTP directories onto the system. The following lists the files and directories related to vsftpd configuration:
/etc/rc.d/init.d/vsftpd — The initialization script (initscript) used by the /sbin/service command to start, stop, or reload vsftpd. Refer to Section 17.2.4, “Starting and Stopping vsftpd” for more information about using this script.
/etc/pam.d/vsftpd — The Pluggable Authentication Modules (PAM) configuration file for vsftpd. This file specifies the requirements a user must meet to login to the FTP server. For more information on PAM, refer to the Using Pluggable Authentication Modules (PAM) chapter of the Red Hat Enterprise Linux 6 Managing Single Sign-On and Smart Cards guide.
/etc/vsftpd/vsftpd.conf — The configuration file for vsftpd. Refer to Section 17.2.5, “ vsftpd Configuration Options” for a list of important options contained within this file.
/etc/vsftpd/ftpusers — A list of users not allowed to log into vsftpd. By default, this list includes the root, bin, and daemon users, among others.
/etc/vsftpd/user_list — This file can be configured to either deny or allow access to the users listed, depending on whether the userlist_deny directive is set to YES (default) or NO in /etc/vsftpd/vsftpd.conf. If /etc/vsftpd/user_list is used to grant access to users, the usernames listed must not appear in /etc/vsftpd/ftpusers.
/var/ftp/ — The directory containing files served by vsftpd. It also contains the /var/ftp/pub/ directory for anonymous users. Both directories are world-readable, but writable only by the root user.
vsftpdvsftpd RPM installs the /etc/rc.d/init.d/vsftpd script, which can be accessed using the service command.
~]# service vsftpd start
~]# service vsftpd stoprestart option is a shorthand way of stopping and then starting vsftpd. This is the most efficient way to make configuration changes take effect after editing the configuration file for vsftpd.
~]# service vsftpd restartcondrestart (conditional restart) option only starts vsftpd if it is currently running. This option is useful for scripts, because it does not start the daemon if it is not running.
~]# service vsftpd condrestartvsftpd service does not start automatically at boot time. To configure the vsftpd service to start at boot time, use an initscript utility, such as /sbin/chkconfig, /usr/sbin/ntsysv, or the Services Configuration Tool program. Refer to Chapter 9, Services and Daemons for more information regarding these tools.
vsftpdFTP domains. This is a technique called multihoming. One way to multihome using vsftpd is by running multiple copies of the daemon, each with its own configuration file.
IP addresses to network devices or alias network devices on the system. Refer to Chapter 7, NetworkManager for more information about configuring network devices and device aliases. Additional information about network configuration scripts can be found in Chapter 8, Network Interfaces.
FTP domains must be configured to reference the correct machine. For information about BIND and its configuration files, refer to Section 13.2, “BIND”.
/etc/vsftpd directory, calling service vsftpd start results in the /etc/rc.d/init.d/vsftpd initscript starting the same number of processes as the number of configuration files. Each configuration file must have a unique name in the /etc/vsftpd/ directory and must be readable and writable only by root.
vsftpd Configuration Optionsvsftpd may not offer the level of customization other widely available FTP servers have, it offers enough options to fill most administrator's needs. The fact that it is not overly feature-laden limits configuration and programmatic errors.
vsftpd is handled by its configuration file, /etc/vsftpd/vsftpd.conf. Each directive is on its own line within the file and follows the following format:
<directive>=<value>
<directive> with a valid directive and <value> with a valid value.
<directive>, equal symbol, and the <value> in a directive.
#) and are ignored by the daemon.
vsftpd.conf.
vsftpd, refer to the Red Hat Enterprise Linux 6 Security Guide.
/etc/vsftpd/vsftpd.conf. All directives not explicitly found or commented out within vsftpd's configuration file are set to their default value.
vsftpd daemon.
listen — When enabled, vsftpd runs in stand-alone mode. Red Hat Enterprise Linux sets this value to YES. This directive cannot be used in conjunction with the listen_ipv6 directive.
NO. On Red Hat Enterprise Linux 6, this option is set to YES in the configuration file.
listen_ipv6 — When enabled, vsftpd runs in stand-alone mode, but listens only to IPv6 sockets. This directive cannot be used in conjunction with the listen directive.
NO.
session_support — When enabled, vsftpd attempts to maintain login sessions for each user through Pluggable Authentication Modules (PAM). For more information, refer to the Using Pluggable Authentication Modules (PAM) chapter of the Red Hat Enterprise Linux 6 Managing Single Sign-On and Smart Cards and the PAM man pages. If session logging is not necessary, disabling this option allows vsftpd to run with less processes and lower privileges.
YES.
anonymous_enable — When enabled, anonymous users are allowed to log in. The usernames anonymous and ftp are accepted.
YES.
banned_email_file — If the deny_email_enable directive is set to YES, this directive specifies the file containing a list of anonymous email passwords which are not permitted access to the server.
/etc/vsftpd/banned_emails.
banner_file — Specifies the file containing text displayed when a connection is established to the server. This option overrides any text specified in the ftpd_banner directive.
cmds_allowed — Specifies a comma-delimited list of FTP commands allowed by the server. All other commands are rejected.
deny_email_enable — When enabled, any anonymous user utilizing email passwords specified in the /etc/vsftpd/banned_emails are denied access to the server. The name of the file referenced by this directive can be specified using the banned_email_file directive.
NO.
ftpd_banner — When enabled, the string specified within this directive is displayed when a connection is established to the server. This option can be overridden by the banner_file directive.
vsftpd displays its standard banner.
local_enable — When enabled, local users are allowed to log into the system.
NO. On Red Hat Enterprise Linux 6, this option is set to YES in the configuration file.
pam_service_name — Specifies the PAM service name for vsftpd.
ftp. On Red Hat Enterprise Linux 6, this option is set to vsftpd in the configuration file.
tcp_wrappers — When enabled, TCP wrappers are used to grant access to the server. If the FTP server is configured on multiple IP addresses, the VSFTPD_LOAD_CONF environment variable can be used to load different configuration files based on the IP address being requested by the client.
NO. On Red Hat Enterprise Linux 6, this option is set to YES in the configuration file.
userlist_deny — When used in conjunction with the userlist_enable directive and set to NO, all local users are denied access unless the username is listed in the file specified by the userlist_file directive. Because access is denied before the client is asked for a password, setting this directive to NO prevents local users from submitting unencrypted passwords over the network.
YES.
userlist_enable — When enabled, the users listed in the file specified by the userlist_file directive are denied access. Because access is denied before the client is asked for a password, users are prevented from submitting unencrypted passwords over the network.
NO. On Red Hat Enterprise Linux 6, this option is set to YES in the configuration file.
userlist_file — Specifies the file referenced by vsftpd when the userlist_enable directive is enabled.
/etc/vsftpd/user_list, which is created during installation.
anonymous_enable directive must be set to YES.
anon_mkdir_write_enable — When enabled in conjunction with the write_enable directive, anonymous users are allowed to create new directories within a parent directory which has write permissions.
NO.
anon_root — Specifies the directory vsftpd changes to after an anonymous user logs in.
anon_upload_enable — When enabled in conjunction with the write_enable directive, anonymous users are allowed to upload files within a parent directory which has write permissions.
NO.
anon_world_readable_only — When enabled, anonymous users are only allowed to download world-readable files.
YES.
ftp_username — Specifies the local user account (listed in /etc/passwd) used for the anonymous FTP user. The home directory specified in /etc/passwd for the user is the root directory of the anonymous FTP user.
ftp.
no_anon_password — When enabled, the anonymous user is not asked for a password.
NO.
secure_email_list_enable — When enabled, only a specified list of email passwords for anonymous logins are accepted. This is a convenient way to offer limited security to public content without the need for virtual users.
/etc/vsftpd/email_passwords. The file format is one password per line, with no trailing white spaces.
NO.
local_enable directive must be set to YES.
chmod_enable — When enabled, the FTP command SITE CHMOD is allowed for local users. This command allows the users to change the permissions on files.
YES.
chroot_list_enable — When enabled, the local users listed in the file specified in the chroot_list_file directive are placed in a chroot jail upon log in.
chroot_local_user directive, the local users listed in the file specified in the chroot_list_file directive are not placed in a chroot jail upon log in.
NO.
chroot_list_file — Specifies the file containing a list of local users referenced when the chroot_list_enable directive is set to YES.
/etc/vsftpd/chroot_list.
chroot_local_user — When enabled, local users are change-rooted to their home directories after logging in.
NO.
chroot_local_user opens up a number of security issues, especially for users with upload privileges. For this reason, it is not recommended.
guest_enable — When enabled, all non-anonymous users are logged in as the user guest, which is the local user specified in the guest_username directive.
NO.
guest_username — Specifies the username the guest user is mapped to.
ftp.
local_root — Specifies the directory vsftpd changes to after a local user logs in.
local_umask — Specifies the umask value for file creation. Note that the default value is in octal form (a numerical system with a base of eight), which includes a "0" prefix. Otherwise the value is treated as a base-10 integer.
077. On Red Hat Enterprise Linux 6, this option is set to 022 in the configuration file.
passwd_chroot_enable — When enabled in conjunction with the chroot_local_user directive, vsftpd change-roots local users based on the occurrence of the /./ in the home directory field within /etc/passwd.
NO.
user_config_dir — Specifies the path to a directory containing configuration files bearing the name of local system users that contain specific setting for that user. Any directive in the user's configuration file overrides those found in /etc/vsftpd/vsftpd.conf.
dirlist_enable — When enabled, users are allowed to view directory lists.
YES.
dirmessage_enable — When enabled, a message is displayed whenever a user enters a directory with a message file. This message resides within the current directory. The name of this file is specified in the message_file directive and is .message by default.
NO. On Red Hat Enterprise Linux 6, this option is set to YES in the configuration file.
force_dot_files — When enabled, files beginning with a dot (.) are listed in directory listings, with the exception of the . and .. files.
NO.
hide_ids — When enabled, all directory listings show ftp as the user and group for each file.
NO.
message_file — Specifies the name of the message file when using the dirmessage_enable directive.
.message.
text_userdb_names — When enabled, text usernames and group names are used in place of UID and GID entries. Enabling this option may slow performance of the server.
NO.
use_localtime — When enabled, directory listings reveal the local time for the computer instead of GMT.
NO.
download_enable — When enabled, file downloads are permitted.
YES.
chown_uploads — When enabled, all files uploaded by anonymous users are owned by the user specified in the chown_username directive.
NO.
chown_username — Specifies the ownership of anonymously uploaded files if the chown_uploads directive is enabled.
root.
write_enable — When enabled, FTP commands which can change the file system are allowed, such as DELE, RNFR, and STOR.
NO. On Red Hat Enterprise Linux 6, this option is set to YES in the configuration file.
vsftpd's logging behavior.
dual_log_enable — When enabled in conjunction with xferlog_enable, vsftpd writes two files simultaneously: a wu-ftpd-compatible log to the file specified in the xferlog_file directive (/var/log/xferlog by default) and a standard vsftpd log file specified in the vsftpd_log_file directive (/var/log/vsftpd.log by default).
NO.
log_ftp_protocol — When enabled in conjunction with xferlog_enable and with xferlog_std_format set to NO, all FTP commands and responses are logged. This directive is useful for debugging.
NO.
syslog_enable — When enabled in conjunction with xferlog_enable, all logging normally written to the standard vsftpd log file specified in the vsftpd_log_file directive (/var/log/vsftpd.log by default) is sent to the system logger instead under the FTPD facility.
NO.
vsftpd_log_file — Specifies the vsftpd log file. For this file to be used, xferlog_enable must be enabled and xferlog_std_format must either be set to NO or, if xferlog_std_format is set to YES, dual_log_enable must be enabled. It is important to note that if syslog_enable is set to YES, the system log is used instead of the file specified in this directive.
/var/log/vsftpd.log.
xferlog_enable — When enabled, vsftpd logs connections (vsftpd format only) and file transfer information to the log file specified in the vsftpd_log_file directive (/var/log/vsftpd.log by default). If xferlog_std_format is set to YES, file transfer information is logged but connections are not, and the log file specified in xferlog_file (/var/log/xferlog by default) is used instead. It is important to note that both log files and log formats are used if dual_log_enable is set to YES.
NO. On Red Hat Enterprise Linux 6, this option is set to YES in the configuration file.
xferlog_file — Specifies the wu-ftpd-compatible log file. For this file to be used, xferlog_enable must be enabled and xferlog_std_format must be set to YES. It is also used if dual_log_enable is set to YES.
/var/log/xferlog.
xferlog_std_format — When enabled in conjunction with xferlog_enable, only a wu-ftpd-compatible file transfer log is written to the file specified in the xferlog_file directive (/var/log/xferlog by default). It is important to note that this file only logs file transfers and does not log connections to the server.
NO. On Red Hat Enterprise Linux 6, this option is set to YES in the configuration file.
wu-ftpd FTP server, the xferlog_std_format directive is set to YES under Red Hat Enterprise Linux. However, this setting means that connections to the server are not logged.
vsftpd format and maintain a wu-ftpd-compatible file transfer log, set dual_log_enable to YES.
wu-ftpd-compatible file transfer log is not important, either set xferlog_std_format to NO, comment the line with a hash sign (#), or delete the line entirely.
vsftpd interacts with the network.
accept_timeout — Specifies the amount of time for a client using passive mode to establish a connection.
60.
anon_max_rate — Specifies the maximum data transfer rate for anonymous users in bytes per second.
0, which does not limit the transfer rate.
connect_from_port_20 When enabled, vsftpd runs with enough privileges to open port 20 on the server during active mode data transfers. Disabling this option allows vsftpd to run with less privileges, but may be incompatible with some FTP clients.
NO. On Red Hat Enterprise Linux 6, this option is set to YES in the configuration file.
connect_timeout — Specifies the maximum amount of time a client using active mode has to respond to a data connection, in seconds.
60.
data_connection_timeout — Specifies maximum amount of time data transfers are allowed to stall, in seconds. Once triggered, the connection to the remote client is closed.
300.
ftp_data_port — Specifies the port used for active data connections when connect_from_port_20 is set to YES.
20.
idle_session_timeout — Specifies the maximum amount of time between commands from a remote client. Once triggered, the connection to the remote client is closed.
300.
listen_address — Specifies the IP address on which vsftpd listens for network connections.
vsftpd serving different IP addresses, the configuration file for each copy of the vsftpd daemon must have a different value for this directive. Refer to Section 17.2.4.1, “Starting Multiple Copies of vsftpd” for more information about multihomed FTP servers.
listen_address6 — Specifies the IPv6 address on which vsftpd listens for network connections when listen_ipv6 is set to YES.
vsftpd serving different IP addresses, the configuration file for each copy of the vsftpd daemon must have a different value for this directive. Refer to Section 17.2.4.1, “Starting Multiple Copies of vsftpd” for more information about multihomed FTP servers.
listen_port — Specifies the port on which vsftpd listens for network connections.
21.
local_max_rate — Specifies the maximum rate data is transferred for local users logged into the server in bytes per second.
0, which does not limit the transfer rate.
max_clients — Specifies the maximum number of simultaneous clients allowed to connect to the server when it is running in standalone mode. Any additional client connections would result in an error message.
0, which does not limit connections.
max_per_ip — Specifies the maximum of clients allowed to connected from the same source IP address.
0, which does not limit connections.
pasv_address — Specifies the IP address for the public facing IP address of the server for servers behind Network Address Translation (NAT) firewalls. This enables vsftpd to hand out the correct return address for passive mode connections.
pasv_enable — When enabled, passive mode connects are allowed.
YES.
pasv_max_port — Specifies the highest possible port sent to the FTP clients for passive mode connections. This setting is used to limit the port range so that firewall rules are easier to create.
0, which does not limit the highest passive port range. The value must not exceed 65535.
pasv_min_port — Specifies the lowest possible port sent to the FTP clients for passive mode connections. This setting is used to limit the port range so that firewall rules are easier to create.
0, which does not limit the lowest passive port range. The value must not be lower 1024.
pasv_promiscuous — When enabled, data connections are not checked to make sure they are originating from the same IP address. This setting is only useful for certain types of tunneling.
IP address as the control connection that initiates the data transfer.
NO.
port_enable — When enabled, active mode connects are allowed.
YES.
vsftpd, refer to the following resources.
/usr/share/doc/vsftpd-<version-number>/ directory — Replace <version-number> with the installed version of the vsftpd package. This directory contains a README with basic information about the software. The TUNING file contains basic performance tuning tips and the SECURITY/ directory contains information about the security model employed by vsftpd.
vsftpd related man pages — There are a number of man pages for the daemon and configuration files. The following lists some of the more important man pages.
man vsftpd — Describes available command line options for vsftpd.
man vsftpd.conf — Contains a detailed list of options available within the configuration file for vsftpd.
man 5 hosts_access — Describes the format and options available within the TCP wrappers configuration files: hosts.allow and hosts.deny.
vsftpd project page is a great place to locate the latest documentation and to contact the author of the software.
FTP.
FTP protocol from the IETF.
system-config-printer command from the command line to start the tool.
New Printer dialog (refer to Section 17.3.2, “Starting Printer Setup”).
New Printer dialog (refer to Section 17.3.1, “Starting the Printer Configuration Tool”).
9100 by default)
New Printer dialog (refer to Section 17.3.2, “Starting Printer Setup”).
New Printer dialog (refer to Section 17.3.2, “Starting Printer Setup”).
New Printer dialog (refer to Section 17.3.2, “Starting Printer Setup”).
computer name/printer share. In Figure 17.8, “Adding a SMB printer”, the computer name is dellbox and the printer share is r2.
guest for Windows servers, or nobody for Samba servers.
Describe Printer enter a unique name for the printer in the Printer Name field. The printer name can contain letters, numbers, dashes (-), and underscores (_); it must not contain any spaces. You can also use the Description and Location fields to add further printer information. Both fields are optional, and may contain spaces.
lpstat -o. The last few lines look similar to the following:
lpstat -o output$ lpstat -o
Charlie-60 twaugh 1024 Tue 08 Feb 2011 16:42:11 GMT
Aaron-61 twaugh 1024 Tue 08 Feb 2011 16:42:44 GMT
Ben-62 root 1024 Tue 08 Feb 2011 16:45:42 GMTlpstat -o and then use the command cancel job number. For example, cancel 60 would cancel the print job in Example 17.1, “Example of lpstat -o output”. You can not cancel print jobs that were started by other users with the cancel command. However, you can enforce deletion of such job by issuing the cancel -U root job_number command. To prevent such canceling change the printer operation policy to Authenticated to force root authentication.
lp sample.txt prints the text file sample.txt. The print filter determines what type of file it is and converts it into a format the printer can understand.
man lplpr command that allows you to print files from the command line.
man cancelman mpageman cupsdman cupsd.confman classes.confman lpstatlpstat command, which displays status information about classes, jobs, and printers.
Table of Contents
ps ax command displays a list of current system processes, including processes owned by other users. To display the owner alongside each process, use the ps aux command. This list is a static list; in other words, it is a snapshot of what was running when you invoked the command. If you want a constantly updated list of running processes, use top as described below.
ps output can be long. To prevent it from scrolling off the screen, you can pipe it through less:
psaux|less
ps command in combination with the grep command to see if a process is running. For example, to determine if Emacs is running, use the following command:
psax|grepemacs
top command displays currently running processes and important information about them including their memory and CPU usage. The list is both real-time and interactive. An example of output from the top command is provided as follows:
~]$ top
top - 18:11:48 up 1 min, 1 user, load average: 0.68, 0.30, 0.11
Tasks: 122 total, 1 running, 121 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.0%us, 0.5%sy, 0.0%ni, 93.4%id, 5.7%wa, 0.2%hi, 0.2%si, 0.0
Mem: 501924k total, 376496k used, 125428k free, 29664k buffers
Swap: 1015800k total, 0k used, 1015800k free, 189008k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1601 root 40 0 20172 1084 920 S 0.3 0.2 0:00.08 hald-addon-sto
1998 silas 40 0 14984 1160 880 R 0.3 0.2 0:00.13 top
1 root 40 0 19160 1412 1156 S 0.0 0.3 0:00.96 init
2 root 40 0 0 0 0 S 0.0 0.0 0:00.01 kthreadd
3 root RT 0 0 0 0 S 0.0 0.0 0:00.05 migration/0
4 root 20 0 0 0 0 S 0.0 0.0 0:00.00 ksoftirqd/0
5 root RT 0 0 0 0 S 0.0 0.0 0:00.00 watchdog/0
6 root RT 0 0 0 0 S 0.0 0.0 0:00.04 migration/1
7 root 20 0 0 0 0 S 0.0 0.0 0:00.00 ksoftirqd/1
8 root RT 0 0 0 0 S 0.0 0.0 0:00.00 watchdog/1
9 root 20 0 0 0 0 S 0.0 0.0 0:00.00 events/0
10 root 20 0 0 0 0 S 0.0 0.0 0:00.01 events/1
11 root 20 0 0 0 0 S 0.0 0.0 0:00.00 cpuset
12 root 20 0 0 0 0 S 0.0 0.0 0:00.00 khelper
[output truncated]top, press the q key.
top. For more information, refer to the top(1) manual page.
| Command | Description |
|---|---|
| Space | Immediately refresh the display |
| h | Display a help screen |
| k | Kill a process. You are prompted for the process ID and the signal to send to it. |
| n | Change the number of processes displayed. You are prompted to enter the number. |
| u | Sort by user. |
| M | Sort by memory usage. |
| P | Sort by CPU usage. |
top, you can use the GNOME System Monitor. To start it from the desktop, select → → or execute gnome-system-monitor at a shell prompt. Select the Processes tab.
free command displays the total amount of physical memory and swap space for the system as well as the amount of memory that is used, free, shared, in kernel buffers, and cached.
~]$ free
total used free shared buffers cached
Mem: 4017660 1619044 2398616 0 59864 637968
-/+ buffers/cache: 921212 3096448
Swap: 3071996 0 3071996free -m shows the same information in megabytes, which are easier to read.
~]$ free -m
total used free shared buffers cached
Mem: 3923 1569 2353 0 58 626
-/+ buffers/cache: 884 3038
Swap: 2999 0 2999free, you can use the GNOME System Monitor. To start it from the desktop, select → → or execute gnome-system-monitor at a shell prompt. Click on the Resources tab.
df command reports the system's disk space usage. If you Execute the command df at a shell prompt, the output looks similar to the following:
~]$ df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/mapper/volgrp1-lvroot
14127024 6868092 6541316 52% /
tmpfs 2008828 592 2008236 1% /dev/shm
/dev/sda1 495844 65047 405197 14% /boot
/dev/mapper/luks-b20f8f7a-7f0f-4497-8de4-81bfa3e541cf
122046576 12111420 103735552 11% /homedf -h. The -h argument stands for human-readable format. The output looks similar to the following:
~]$ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/volgrp1-lvroot
14G 6.6G 6.3G 52% /
tmpfs 2.0G 592K 2.0G 1% /dev/shm
/dev/sda1 485M 64M 396M 14% /boot
/dev/mapper/luks-b20f8f7a-7f0f-4497-8de4-81bfa3e541cf
117G 12G 99G 11% /home/dev/shm. This entry represents the system's virtual memory file system.
du command displays the estimated amount of space being used by files in a directory. If you execute du at a shell prompt, the disk usage for each of the subdirectories is displayed in a list. The grand total for the current directory and subdirectories are also shown as the last line in the list. If you do not want to see the totals for all the subdirectories, use the command du -hs to see only the grand total for the directory in human-readable format. Use the du --help command to see more options.
gnome-system-monitor command at a shell prompt. Select the File Systems tab to view the system's partitions. The figure below illustrates the File Systems tab.
lspci command to list all PCI devices. Use the command lspci -v for more verbose information or lspci -vv for very verbose output.
lspci can be used to determine the manufacturer, model, and memory size of a system's video card:
~]$ lspci -v
[output truncated]
00:02.1 Display controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 07)
Subsystem: Lenovo Device 20e4
Flags: bus master, fast devsel, latency 0
Memory at f4200000 (64-bit, non-prefetchable) [size=1M]
Capabilities: [d0] Power Management version 3
[output truncated]lspci is also useful to determine the network card in your system if you do not know the manufacturer or model number.
| Package | Provides |
|---|---|
| net-snmp | The SNMP Agent Daemon and documentation. This package is required for exporting performance data. |
| net-snmp-libs |
The netsnmp library and the bundled management information bases (MIBs). This package is required for exporting performance data.
|
| net-snmp-utils |
SNMP clients such as snmpget and snmpwalk. This package is required in order to query a system's performance data over SNMP.
|
| net-snmp-perl |
The mib2c utility and the NetSNMP Perl module.
|
| net-snmp-python | An SNMP client library for Python. |
yum command in the following form:
yuminstallpackage…
~]# yum install net-snmp net-snmp-libs net-snmp-utilsroot) to run this command. For more information on how to install new packages in Red Hat Enterprise Linux, refer to Section 5.2.4, “Installing Packages”.
snmpd, the SNMP Agent Daemon. This section provides information on how to start, stop, and restart the snmpd service, and shows how to enable it in a particular runlevel. For more information on the concept of runlevels and how to manage system services in Red Hat Enterprise Linux in general, refer to Chapter 9, Services and Daemons.
snmpd service in the current session, type the following at a shell prompt as root:
servicesnmpdstart
chkconfigsnmpdon
snmpd service, type the following at a shell prompt as root:
servicesnmpdstop
chkconfigsnmpdoff
snmpd service, type the following at a shell prompt:
servicesnmpdrestart
servicesnmpdreload
snmpd service to reload the configuration.
/etc/snmp/snmpd.conf configuration file. The default snmpd.conf file shipped with Red Hat Enterprise Linux 6 is heavily commented and serves as a good starting point for agent configuration.
snmpconf which can be used to interactively generate a valid agent configuration.
snmpwalk utility described in this section.
snmpd service to re-read the configuration by running the following command as root:
servicesnmpdreload
system tree. For example, the following snmpwalk command shows the system tree with a default agent configuration.
~]# snmpwalk -v2c -c public localhost system
SNMPv2-MIB::sysDescr.0 = STRING: Linux localhost.localdomain 2.6.32-122.el6.x86_64 #1 SMP Wed Mar 9 23:54:34 EST 2011 x86_64
SNMPv2-MIB::sysObjectID.0 = OID: NET-SNMP-MIB::netSnmpAgentOIDs.10
DISMAN-EVENT-MIB::sysUpTimeInstance = Timeticks: (99554) 0:16:35.54
SNMPv2-MIB::sysContact.0 = STRING: Root <root@localhost> (configure /etc/snmp/snmp.local.conf)
SNMPv2-MIB::sysName.0 = STRING: localhost.localdomain
SNMPv2-MIB::sysLocation.0 = STRING: Unknown (edit /etc/snmp/snmpd.conf)sysName object is set to the hostname. The sysLocation and sysContact objects can be configured in the /etc/snmp/snmpd.conf file by changing the value of the syslocation and syscontact directives, for example:
syslocation Datacenter, Row 3, Rack 2 syscontact UNIX Admin <admin@example.com>
snmpwalk command again:
~]#service snmpd reloadReloading snmpd: [ OK ] ~]#snmpwalk -v2c -c public localhost systemSNMPv2-MIB::sysDescr.0 = STRING: Linux localhost.localdomain 2.6.32-122.el6.x86_64 #1 SMP Wed Mar 9 23:54:34 EST 2011 x86_64 SNMPv2-MIB::sysObjectID.0 = OID: NET-SNMP-MIB::netSnmpAgentOIDs.10 DISMAN-EVENT-MIB::sysUpTimeInstance = Timeticks: (158357) 0:26:23.57 SNMPv2-MIB::sysContact.0 = STRING: UNIX Admin <admin@example.com> SNMPv2-MIB::sysName.0 = STRING: localhost.localdomain SNMPv2-MIB::sysLocation.0 = STRING: Datacenter, Row 3, Rack 2
rocommunity or rwcommunity directive in the /etc/snmp/snmpd.conf configuration file. The format of the directives is the following:
directivecommunity[source[OID]]
community is the community string to use, source is an IP address or subnet, and OID is the SNMP tree to provide access to. For example, the following directive provides read-only access to the system tree to a client using the community string “redhat” on the local machine:
rocommunity redhat 127.0.0.1 .1.3.6.1.2.1.1
snmpwalk command with the -v and -c options.
~]# snmpwalk -v2c -c redhat localhost system
SNMPv2-MIB::sysDescr.0 = STRING: Linux localhost.localdomain 2.6.32-122.el6.x86_64 #1 SMP Wed Mar 9 23:54:34 EST 2011 x86_64
SNMPv2-MIB::sysObjectID.0 = OID: NET-SNMP-MIB::netSnmpAgentOIDs.10
DISMAN-EVENT-MIB::sysUpTimeInstance = Timeticks: (158357) 0:26:23.57
SNMPv2-MIB::sysContact.0 = STRING: UNIX Admin <admin@example.com>
SNMPv2-MIB::sysName.0 = STRING: localhost.localdomain
SNMPv2-MIB::sysLocation.0 = STRING: Datacenter, Row 3, Rack 2net-snmp-create-v3-user command. This command adds entries to the /var/lib/net-snmp/snmpd.conf and /etc/snmp/snmpd.conf files which create the user and grant access to the user. Note that the net-snmp-create-v3-user command may only be run when the agent is not running. The following example creates the “sysadmin” user with the password “redhatsnmp”:
~]#service snmpd stopStopping snmpd: [ OK ] ~]#net-snmp-create-v3-userEnter a SNMPv3 user name to create: admin Enter authentication pass-phrase: redhatsnmp Enter encryption pass-phrase: [press return to reuse the authentication pass-phrase] adding the following line to /var/lib/net-snmp/snmpd.conf: createUser admin MD5 "redhatsnmp" DES adding the following line to /etc/snmp/snmpd.conf: rwuser admin ~]#service snmpd startStarting snmpd: [ OK ]
rwuser directive (or rouser when the -ro command line option is supplied) that net-snmp-create-v3-user adds to /etc/snmp/snmpd.conf has a similar format to the rwcommunity and rocommunity directives:
directiveuser[noauth|auth|priv] [OID]
user is a username and OID is the SNMP tree to provide access to. By default, the Net-SNMP Agent Daemon allows only authenticated requests (the auth option). The noauth option allows you to permit unauthenticated requests, and the priv option enforces the use of encryption. The authpriv option specifies that requests must be authenticated and replies should be encrypted.
rwuser admin authpriv .1
.snmp directory in your user's home directory and a configuration file named snmp.conf in that directory (~/.snmp/snmp.conf) with the following lines:
defVersion 3 defSecurityLevel authPriv defSecurityName admin defPassphrase redhatsnmp
snmpwalk command will now use these authentication settings when querying the agent:
~]$ snmpwalk -v3 localhost system
SNMPv2-MIB::sysDescr.0 = STRING: Linux localhost.localdomain 2.6.32-122.el6.x86_64 #1 SMP Wed Mar 9 23:54:34 EST 2011 x86_64
[output truncated]Host Resources MIB included with Net-SNMP presents information about the current hardware and software configuration of a host to a client utility. Table 18.3, “Available OIDs” summarizes the different OIDs available under that MIB.
| OID | Description |
|---|---|
HOST-RESOURCES-MIB::hrSystem
| Contains general system information such as uptime, number of users, and number of running processes. |
HOST-RESOURCES-MIB::hrStorage
| Contains data on memory and file system usage. |
HOST-RESOURCES-MIB::hrDevices
| Contains a listing of all processors, network devices, and file systems. |
HOST-RESOURCES-MIB::hrSWRun
| Contains a listing of all running processes. |
HOST-RESOURCES-MIB::hrSWRunPerf
| Contains memory and CPU statistics on the process table from HOST-RESOURCES-MIB::hrSWRun. |
HOST-RESOURCES-MIB::hrSWInstalled
| Contains a listing of the RPM database. |
HOST-RESOURCES-MIB::hrFSTable:
~]$ snmptable -Cb localhost HOST-RESOURCES-MIB::hrFSTable
SNMP table: HOST-RESOURCES-MIB::hrFSTable
Index MountPoint RemoteMountPoint Type
Access Bootable StorageIndex LastFullBackupDate LastPartialBackupDate
1 "/" "" HOST-RESOURCES-TYPES::hrFSLinuxExt2
readWrite true 31 0-1-1,0:0:0.0 0-1-1,0:0:0.0
5 "/dev/shm" "" HOST-RESOURCES-TYPES::hrFSOther
readWrite false 35 0-1-1,0:0:0.0 0-1-1,0:0:0.0
6 "/boot" "" HOST-RESOURCES-TYPES::hrFSLinuxExt2
readWrite false 36 0-1-1,0:0:0.0 0-1-1,0:0:0.0HOST-RESOURCES-MIB, see the /usr/share/snmp/mibs/HOST-RESOURCES-MIB.txt file.
UCD SNMP MIB. The systemStats OID provides a number of counters around processor usage:
~]$ snmpwalk localhost UCD-SNMP-MIB::systemStats
UCD-SNMP-MIB::ssIndex.0 = INTEGER: 1
UCD-SNMP-MIB::ssErrorName.0 = STRING: systemStats
UCD-SNMP-MIB::ssSwapIn.0 = INTEGER: 0 kB
UCD-SNMP-MIB::ssSwapOut.0 = INTEGER: 0 kB
UCD-SNMP-MIB::ssIOSent.0 = INTEGER: 0 blocks/s
UCD-SNMP-MIB::ssIOReceive.0 = INTEGER: 0 blocks/s
UCD-SNMP-MIB::ssSysInterrupts.0 = INTEGER: 29 interrupts/s
UCD-SNMP-MIB::ssSysContext.0 = INTEGER: 18 switches/s
UCD-SNMP-MIB::ssCpuUser.0 = INTEGER: 0
UCD-SNMP-MIB::ssCpuSystem.0 = INTEGER: 0
UCD-SNMP-MIB::ssCpuIdle.0 = INTEGER: 99
UCD-SNMP-MIB::ssCpuRawUser.0 = Counter32: 2278
UCD-SNMP-MIB::ssCpuRawNice.0 = Counter32: 1395
UCD-SNMP-MIB::ssCpuRawSystem.0 = Counter32: 6826
UCD-SNMP-MIB::ssCpuRawIdle.0 = Counter32: 3383736
UCD-SNMP-MIB::ssCpuRawWait.0 = Counter32: 7629
UCD-SNMP-MIB::ssCpuRawKernel.0 = Counter32: 0
UCD-SNMP-MIB::ssCpuRawInterrupt.0 = Counter32: 434
UCD-SNMP-MIB::ssIORawSent.0 = Counter32: 266770
UCD-SNMP-MIB::ssIORawReceived.0 = Counter32: 427302
UCD-SNMP-MIB::ssRawInterrupts.0 = Counter32: 743442
UCD-SNMP-MIB::ssRawContexts.0 = Counter32: 718557
UCD-SNMP-MIB::ssCpuRawSoftIRQ.0 = Counter32: 128
UCD-SNMP-MIB::ssRawSwapIn.0 = Counter32: 0
UCD-SNMP-MIB::ssRawSwapOut.0 = Counter32: 0ssCpuRawUser, ssCpuRawSystem, ssCpuRawWait, and ssCpuRawIdle OIDs provide counters which are helpful when determining whether a system is spending most of its processor time in kernel space, user space, or I/O. ssRawSwapIn and ssRawSwapOut can be helpful when determining whether a system is suffering from memory exhaustion.
UCD-SNMP-MIB::memory OID, which provides similar data to the free command:
~]$ snmpwalk localhost UCD-SNMP-MIB::memory
UCD-SNMP-MIB::memIndex.0 = INTEGER: 0
UCD-SNMP-MIB::memErrorName.0 = STRING: swap
UCD-SNMP-MIB::memTotalSwap.0 = INTEGER: 1023992 kB
UCD-SNMP-MIB::memAvailSwap.0 = INTEGER: 1023992 kB
UCD-SNMP-MIB::memTotalReal.0 = INTEGER: 1021588 kB
UCD-SNMP-MIB::memAvailReal.0 = INTEGER: 634260 kB
UCD-SNMP-MIB::memTotalFree.0 = INTEGER: 1658252 kB
UCD-SNMP-MIB::memMinimumSwap.0 = INTEGER: 16000 kB
UCD-SNMP-MIB::memBuffer.0 = INTEGER: 30760 kB
UCD-SNMP-MIB::memCached.0 = INTEGER: 216200 kB
UCD-SNMP-MIB::memSwapError.0 = INTEGER: noError(0)
UCD-SNMP-MIB::memSwapErrorMsg.0 = STRING:UCD SNMP MIB. The SNMP table UCD-SNMP-MIB::laTable has a listing of the 1, 5, and 15 minute load averages:
~]$ snmptable localhost UCD-SNMP-MIB::laTable
SNMP table: UCD-SNMP-MIB::laTable
laIndex laNames laLoad laConfig laLoadInt laLoadFloat laErrorFlag laErrMessage
1 Load-1 0.00 12.00 0 0.000000 noError
2 Load-5 0.00 12.00 0 0.000000 noError
3 Load-15 0.00 12.00 0 0.000000 noErrorHost Resources MIB provides information on file system size and usage. Each file system (and also each memory pool) has an entry in the HOST-RESOURCES-MIB::hrStorageTable table:
~]$ snmptable -Cb localhost HOST-RESOURCES-MIB::hrStorageTable
SNMP table: HOST-RESOURCES-MIB::hrStorageTable
Index Type Descr
AllocationUnits Size Used AllocationFailures
1 HOST-RESOURCES-TYPES::hrStorageRam Physical memory
1024 Bytes 1021588 388064 ?
3 HOST-RESOURCES-TYPES::hrStorageVirtualMemory Virtual memory
1024 Bytes 2045580 388064 ?
6 HOST-RESOURCES-TYPES::hrStorageOther Memory buffers
1024 Bytes 1021588 31048 ?
7 HOST-RESOURCES-TYPES::hrStorageOther Cached memory
1024 Bytes 216604 216604 ?
10 HOST-RESOURCES-TYPES::hrStorageVirtualMemory Swap space
1024 Bytes 1023992 0 ?
31 HOST-RESOURCES-TYPES::hrStorageFixedDisk /
4096 Bytes 2277614 250391 ?
35 HOST-RESOURCES-TYPES::hrStorageFixedDisk /dev/shm
4096 Bytes 127698 0 ?
36 HOST-RESOURCES-TYPES::hrStorageFixedDisk /boot
1024 Bytes 198337 26694 ?HOST-RESOURCES-MIB::hrStorageSize and HOST-RESOURCES-MIB::hrStorageUsed can be used to calculate the remaining capacity of each mounted file system.
UCD-SNMP-MIB::systemStats (ssIORawSent.0 and ssIORawRecieved.0) and in UCD-DISKIO-MIB::diskIOTable. The latter provides much more granular data. Under this table are OIDs for diskIONReadX and diskIONWrittenX, which provide counters for the number of bytes read from and written to the block device in question since the system boot:
~]$ snmptable -Cb localhost UCD-DISKIO-MIB::diskIOTable
SNMP table: UCD-DISKIO-MIB::diskIOTable
Index Device NRead NWritten Reads Writes LA1 LA5 LA15 NReadX NWrittenX
...
25 sda 216886272 139109376 16409 4894 ? ? ? 216886272 139109376
26 sda1 2455552 5120 613 2 ? ? ? 2455552 5120
27 sda2 1486848 0 332 0 ? ? ? 1486848 0
28 sda3 212321280 139104256 15312 4871 ? ? ? 212321280 139104256IF-MIB::ifTable provides an SNMP table with an entry for each interface on the system, the configuration of the interface, and various packet counters for the interface. The following example shows the first few columns of ifTable on a system with two physical network interfaces:
~]$ snmptable -Cb localhost IF-MIB::ifTable
SNMP table: IF-MIB::ifTable
Index Descr Type Mtu Speed PhysAddress AdminStatus
1 lo softwareLoopback 16436 10000000 up
2 eth0 ethernetCsmacd 1500 0 52:54:0:c7:69:58 up
3 eth1 ethernetCsmacd 1500 0 52:54:0:a7:a3:24 downIF-MIB::ifOutOctets and IF-MIB::ifInOctets. The following SNMP queries will retrieve network traffic for each of the interfaces on this system:
~]$snmpwalk localhost IF-MIB::ifDescrIF-MIB::ifDescr.1 = STRING: lo IF-MIB::ifDescr.2 = STRING: eth0 IF-MIB::ifDescr.3 = STRING: eth1 ~]$snmpwalk localhost IF-MIB::ifOutOctetsIF-MIB::ifOutOctets.1 = Counter32: 10060699 IF-MIB::ifOutOctets.2 = Counter32: 650 IF-MIB::ifOutOctets.3 = Counter32: 0 ~]$snmpwalk localhost IF-MIB::ifInOctetsIF-MIB::ifInOctets.1 = Counter32: 10060699 IF-MIB::ifInOctets.2 = Counter32: 78650 IF-MIB::ifInOctets.3 = Counter32: 0
NET-SNMP-EXTEND-MIB) that can be used to query arbitrary shell scripts. To specify the shell script to run, use the extend directive in the /etc/snmp/snmpd.conf file. Once defined, the Agent will provide the exit code and any output of the command over SNMP. The example below demonstrates this mechanism with a script which determines the number of httpd processes in the process table.
proc directive. Refer to the snmpd.conf(5) manual page for more information.
httpd processes running on the system at a given point in time:
#!/bin/sh NUMPIDS=`pgrep httpd | wc -l` exit $NUMPIDS
extend directive to the /etc/snmp/snmpd.conf file. The format of the extend directive is the following:
extendnameprogargs
name is an identifying string for the extension, prog is the program to run, and args are the arguments to give the program. For instance, if the above shell script is copied to /usr/local/bin/check_apache.sh, the following directive will add the script to the SNMP tree:
extend httpd_pids /bin/sh /usr/local/bin/check_apache.sh
NET-SNMP-EXTEND-MIB::nsExtendObjects:
~]$ snmpwalk localhost NET-SNMP-EXTEND-MIB::nsExtendObjects
NET-SNMP-EXTEND-MIB::nsExtendNumEntries.0 = INTEGER: 1
NET-SNMP-EXTEND-MIB::nsExtendCommand."httpd_pids" = STRING: /bin/sh
NET-SNMP-EXTEND-MIB::nsExtendArgs."httpd_pids" = STRING: /usr/local/bin/check_apache.sh
NET-SNMP-EXTEND-MIB::nsExtendInput."httpd_pids" = STRING:
NET-SNMP-EXTEND-MIB::nsExtendCacheTime."httpd_pids" = INTEGER: 5
NET-SNMP-EXTEND-MIB::nsExtendExecType."httpd_pids" = INTEGER: exec(1)
NET-SNMP-EXTEND-MIB::nsExtendRunType."httpd_pids" = INTEGER: run-on-read(1)
NET-SNMP-EXTEND-MIB::nsExtendStorage."httpd_pids" = INTEGER: permanent(4)
NET-SNMP-EXTEND-MIB::nsExtendStatus."httpd_pids" = INTEGER: active(1)
NET-SNMP-EXTEND-MIB::nsExtendOutput1Line."httpd_pids" = STRING:
NET-SNMP-EXTEND-MIB::nsExtendOutputFull."httpd_pids" = STRING:
NET-SNMP-EXTEND-MIB::nsExtendOutNumLines."httpd_pids" = INTEGER: 1
NET-SNMP-EXTEND-MIB::nsExtendResult."httpd_pids" = INTEGER: 8
NET-SNMP-EXTEND-MIB::nsExtendOutLine."httpd_pids".1 = STRING:extend directive. For example, the following shell script can be used to determine the number of processes matching an arbitrary string, and will also output a text string giving the number of processes:
#!/bin/sh PATTERN=$1 NUMPIDS=`pgrep $PATTERN | wc -l` echo "There are $NUMPIDS $PATTERN processes." exit $NUMPIDS
/etc/snmp/snmpd.conf directives will give both the number of httpd PIDs as well as the number of snmpd PIDs when the above script is copied to /usr/local/bin/check_proc.sh:
extend httpd_pids /bin/sh /usr/local/bin/check_proc.sh httpd extend snmpd_pids /bin/sh /usr/local/bin/check_proc.sh snmpd
snmpwalk of the nsExtendObjects OID:
~]$ snmpwalk localhost NET-SNMP-EXTEND-MIB::nsExtendObjects
NET-SNMP-EXTEND-MIB::nsExtendNumEntries.0 = INTEGER: 2
NET-SNMP-EXTEND-MIB::nsExtendCommand."httpd_pids" = STRING: /bin/sh
NET-SNMP-EXTEND-MIB::nsExtendCommand."snmpd_pids" = STRING: /bin/sh
NET-SNMP-EXTEND-MIB::nsExtendArgs."httpd_pids" = STRING: /usr/local/bin/check_proc.sh httpd
NET-SNMP-EXTEND-MIB::nsExtendArgs."snmpd_pids" = STRING: /usr/local/bin/check_proc.sh snmpd
NET-SNMP-EXTEND-MIB::nsExtendInput."httpd_pids" = STRING:
NET-SNMP-EXTEND-MIB::nsExtendInput."snmpd_pids" = STRING:
...
NET-SNMP-EXTEND-MIB::nsExtendResult."httpd_pids" = INTEGER: 8
NET-SNMP-EXTEND-MIB::nsExtendResult."snmpd_pids" = INTEGER: 1
NET-SNMP-EXTEND-MIB::nsExtendOutLine."httpd_pids".1 = STRING: There are 8 httpd processes.
NET-SNMP-EXTEND-MIB::nsExtendOutLine."snmpd_pids".1 = STRING: There are 1 snmpd processes.httpd processes. This query could be used during a performance test to determine the impact of the number of processes on memory pressure:
~]$snmpget localhost \'NET-SNMP-EXTEND-MIB::nsExtendResult."httpd_pids"' \UCD-SNMP-MIB::memAvailReal.0NET-SNMP-EXTEND-MIB::nsExtendResult."httpd_pids" = INTEGER: 8 UCD-SNMP-MIB::memAvailReal.0 = INTEGER: 799664 kB
extend directive is a fairly limited method for exposing custom application metrics over SNMP. The Net-SNMP Agent also provides an embedded Perl interface for exposing custom objects. The net-snmp-perl package provides the NetSNMP::agent Perl module that is used to write embedded Perl plug-ins on Red Hat Enterprise Linux.
NetSNMP::agent Perl module provides an agent object which is used to handle requests for a part of the agent's OID tree. The agent object's constructor has options for running the agent as a sub-agent of snmpd or a standalone agent. No arguments are necessary to create an embedded agent:
use NetSNMP::agent (':all'); my $agent = new NetSNMP::agent();
agent object has a register method which is used to register a callback function with a particular OID. The register function takes a name, OID, and pointer to the callback function. The following example will register a callback function named hello_handler with the SNMP Agent which will handle requests under the OID .1.3.6.1.4.1.8072.9999.9999:
$agent->register("hello_world", ".1.3.6.1.4.1.8072.9999.9999", \&hello_handler);
.1.3.6.1.4.1.8072.9999.9999 (NET-SNMP-MIB::netSnmpPlaypen) is typically used for demonstration purposes only. If your organization does not already have a root OID, you can obtain one by contacting your Name Registration Authority (ANSI in the United States).
HANDLER, REGISTRATION_INFO, REQUEST_INFO, and REQUESTS. The REQUESTS parameter contains a list of requests in the current call and should be iterated over and populated with data. The request objects in the list have get and set methods which allow for manipulating the OID and value of the request. For example, the following call will set the value of a request object to the string “hello world”:
$request->setValue(ASN_OCTET_STR, "hello world");
getMode method on the request_info object passed as the third parameter to the handler function. If the request is a GET request, the caller will expect the handler to set the value of the request object, depending on the OID of the request. If the request is a GETNEXT request, the caller will also expect the handler to set the OID of the request to the next available OID in the tree. This is illustrated in the following code example:
my $request; my $string_value = "hello world"; my $integer_value = "8675309"; for($request = $requests; $request; $request = $request->next()) { my $oid = $request->getOID(); if ($request_info->getMode() == MODE_GET) { if ($oid == new NetSNMP::OID(".1.3.6.1.4.1.8072.9999.9999.1.0")) { $request->setValue(ASN_OCTET_STR, $string_value); } elsif ($oid == new NetSNMP::OID(".1.3.6.1.4.1.8072.9999.9999.1.1")) { $request->setValue(ASN_INTEGER, $integer_value); } } elsif ($request_info->getMode() == MODE_GETNEXT) { if ($oid == new NetSNMP::OID(".1.3.6.1.4.1.8072.9999.9999.1.0")) { $request->setOID(".1.3.6.1.4.1.8072.9999.9999.1.1"); $request->setValue(ASN_INTEGER, $integer_value); } elsif ($oid < new NetSNMP::OID(".1.3.6.1.4.1.8072.9999.9999.1.0")) { $request->setOID(".1.3.6.1.4.1.8072.9999.9999.1.0"); $request->setValue(ASN_OCTET_STR, $string_value); } } }
getMode returns MODE_GET, the handler analyzes the value of the getOID call on the request object. The value of the request is set to either string_value if the OID ends in “.1.0”, or set to integer_value if the OID ends in “.1.1”. If the getMode returns MODE_GETNEXT, the handler determines whether the OID of the request is “.1.0”, and then sets the OID and value for “.1.1”. If the request is higher on the tree than “.1.0”, the OID and value for “.1.0” is set. This in effect returns the “next” value in the tree so that a program like snmpwalk can traverse the tree without prior knowledge of the structure.
NetSNMP::ASN. See the perldoc for NetSNMP::ASN for a full list of available constants.
#!/usr/bin/perl use NetSNMP::agent (':all'); use NetSNMP::ASN qw(ASN_OCTET_STR ASN_INTEGER); sub hello_handler { my ($handler, $registration_info, $request_info, $requests) = @_; my $request; my $string_value = "hello world"; my $integer_value = "8675309"; for($request = $requests; $request; $request = $request->next()) { my $oid = $request->getOID(); if ($request_info->getMode() == MODE_GET) { if ($oid == new NetSNMP::OID(".1.3.6.1.4.1.8072.9999.9999.1.0")) { $request->setValue(ASN_OCTET_STR, $string_value); } elsif ($oid == new NetSNMP::OID(".1.3.6.1.4.1.8072.9999.9999.1.1")) { $request->setValue(ASN_INTEGER, $integer_value); } } elsif ($request_info->getMode() == MODE_GETNEXT) { if ($oid == new NetSNMP::OID(".1.3.6.1.4.1.8072.9999.9999.1.0")) { $request->setOID(".1.3.6.1.4.1.8072.9999.9999.1.1"); $request->setValue(ASN_INTEGER, $integer_value); } elsif ($oid < new NetSNMP::OID(".1.3.6.1.4.1.8072.9999.9999.1.0")) { $request->setOID(".1.3.6.1.4.1.8072.9999.9999.1.0"); $request->setValue(ASN_OCTET_STR, $string_value); } } } } my $agent = new NetSNMP::agent(); $agent->register("hello_world", ".1.3.6.1.4.1.8072.9999.9999", \&hello_handler);
/usr/share/snmp/hello_world.pl and add the following line to the /etc/snmp/snmpd.conf configuration file:
perl do "/usr/share/snmp/hello_world.pl"
snmpwalk should return the new data:
~]$ snmpwalk localhost NET-SNMP-MIB::netSnmpPlaypen
NET-SNMP-MIB::netSnmpPlaypen.1.0 = STRING: "hello world"
NET-SNMP-MIB::netSnmpPlaypen.1.1 = INTEGER: 8675309snmpget should also be used to exercise the other mode of the handler:
~]$snmpget localhost \NET-SNMP-MIB::netSnmpPlaypen.1.0 \NET-SNMP-MIB::netSnmpPlaypen.1.1NET-SNMP-MIB::netSnmpPlaypen.1.0 = STRING: "hello world" NET-SNMP-MIB::netSnmpPlaypen.1.1 = INTEGER: 8675309
ps command.
top command.
free command.
df command.
du command.
lspci command.
snmpd service.
/etc/snmp/snmpd.conf file containing full documentation of available configuration directives.
rsyslogd. A list of log files maintained by rsyslogd can be found in the /etc/rsyslog.conf configuration file.
sysklogd daemon. rsyslog supports the same functionality as sysklogd and extends it with enhanced filtering, encryption protected relaying of messages, various configuration options, or support for transportation via the TCP or UDP protocols. Note that rsyslog is compatible with sysklogd.
/etc/rsyslog.conf. It consists of global directives, rules or comments (any empty lines or any text following a hash sign (#)). Both, global directives and rules are extensively described in the sections below.
rsyslogd daemon. They usually specify a value for a specific pre-defined variable that affects the behavior of the rsyslogd daemon or a rule that follows. All of the global directives must start with a dollar sign ($). Only one directive can be specified per line. The following is an example of a global directive that specifies the maximum size of the syslog message queue:
$MainMsgQueueSize 50000
10,000 messages) can be overridden by specifying a different value (as shown in the example above).
/etc/rsyslog.conf configuration file. A directive affects the behavior of all configuration options until another occurrence of that same directive is detected.
/usr/share/doc/rsyslog-<version-number>/rsyslog_conf_global.html.
$ModLoad <MODULE>$ModLoad is the global directive that loads the specified module and <MODULE> represents your desired module. For example, if you want to load the Text File Input Module (imfile — enables rsyslog to convert any standard text files into syslog messages), specify the following line in your /etc/rsyslog.conf configuration file:
$ModLoad imfile
im prefix, such as imfile, imrelp, etc.
om prefix, such as omsnmp, omrelp, etc.
fm prefix.
pm prefix, such as pmrfc5424, pmrfc3164, etc.
sm prefix, such as smfile, smtradfile, etc.
/etc/rsyslog.conf configuration file, define both, a filter and an action, on one line and separate them with one or more spaces or tabs. For more information on filters, refer to Section 19.1.3.1, “Filter Conditions” and for information on actions, refer to Section 19.1.3.2, “Actions”.
<FACILITY>.<PRIORITY>
<FACILITY> specifies the subsystem that produces a specific syslog message. For example, the mail subsystem handles all mail related syslog messages. <FACILITY> can be represented by one of these keywords: auth, authpriv, cron, daemon, kern, lpr, mail, news, syslog, user, uucp, and local0 through local7.
<PRIORITY> specifies a priority of a syslog message. <PRIORITY> can be represented by one of these keywords (listed in an ascending order): debug, info, notice, warning, err, crit, alert, and emerg.
=), you specify that only syslog messages with that priority will be selected. All other priorities will be ignored. Conversely, preceding a priority with an exclamation mark (!) selects all syslog messages but those with the defined priority. By not using either of these two extensions, you specify a selection of syslog messages with the defined or higher priority.
*) to define all facilities or priorities (depending on where you place the asterisk, before or after the dot). Specifying the keyword none serves for facilities with no given priorities.
,). To define multiple filters on one line, separate them with a semi-colon (;).
kern.* # Selects all kernel syslog messages with any priority
mail.crit # Selects all mail syslog messages with priority crit and higher.
cron.!info,!debug # Selects all cron syslog messages except those with theinfoordebugpriority.
timegenerated or syslogtag. For more information on properties, refer to Section 19.1.3.3.2, “Properties”. Each of the properties specified in the filters lets you compare it to a specific value using one of the compare-operations listed in Table 19.1, “Property-based compare-operations”.
| Compare-operation | Description |
|---|---|
contains
| Checks whether the provided string matches any part of the text provided by the property. |
isequal
| Compares the provided string against all of the text provided by the property. |
startswith
| Checks whether the provided string matches a prefix of the text provided by the property. |
regex
| Compares the provided POSIX BRE (Basic Regular Expression) regular expression against the text provided by the property. |
ereregex
| Compares the provided POSIX ERE (Extended Regular Expression) regular expression against the text provided by the property. |
:<PROPERTY>, [!]<COMPARE_OPERATION>, "<STRING>"
<PROPERTY> attribute specifies the desired property (for example, timegenerated, hostname, etc.).
!) negates the output of the compare-operation (if prefixing the compare-operation).
<COMPARE_OPERATION> attribute specifies one of the compare-operations listed in Table 19.1, “Property-based compare-operations”.
<STRING> attribute specifies the value that the text provided by the property is compared to. To escape certain character (for example a quotation mark (")), use the backslash character (\).
error in their message text:
:msg, contains, "error"
host1:
:hostname, isequal, "host1"
fatal and error with any or no text between them (for example, fatal lib error):
:msg, !regex, "fatal .* error"
/usr/share/doc/rsyslog-<version-number>/rscript_abnf.html along with examples of various expression-based filters.
if<EXPRESSION>then<ACTION>
<EXPRESSION> attribute represents an expression to be evaluated, for example: $msg startswith 'DEVNAME' or $syslogfacility-text == 'local0'.
<ACTION> attribute represents an action to be performed if the expression returns the value true.
/etc/rsyslog.conf configuration file. Each block consists of rules which are preceded with a program or hostname label. Use the '!<PROGRAM>' or '-<PROGRAM>' labels to include or exclude programs, respectively. Use the '+<HOSTNAME> ' or '-<HOSTNAME> ' labels include or exclude hostnames, respectively.
!yum *.* /var/log/named.log
/var/log/cron.log log file:
cron.* /var/log/cron.log
-) as a prefix of the file path you specified if you want to omit syncing the desired log file after every syslog message is generated.
?) prefix. For more information on templates, refer to Section 19.1.3.3.1, “Generating dynamic file names”.
/dev/console device, syslog messages are sent to standard output (using special tty-handling) or your console (using special /dev/console-handling) when using the X Window System, respectively.
@[(<OPTION>)]<HOST>:[<PORT>]
@) indicates that the syslog messages are forwarded to a host using the UDP protocol. To use the TCP protocol, use two at signs with no space between them (@@).
<OPTION> attribute can be replaced with an option such as z<NUMBER>. This option enables zlib compression for syslog messages; the <NUMBER> attribute specifies the level of compression. To define multiple options, simply separate each one of them with a comma (,).
<HOST> attribute specifies the host which receives the selected syslog messages.
<PORT> attribute specifies the host machine's port.
IPv6 address as the host, enclose the address in square brackets ([, ]).
*.* @192.168.0.1 # Forwards messages to 192.168.0.1 via the UDP protocol*.* @@example.com:18 # Forwards messages to "example.com" using port 18 and the TCP protocol
*.* @(z9)[2001::1] # Compresses messages with zlib (level 9 compression)
# and forwards them to 2001::1 using the UDP protocol$outchannel<NAME>,<FILE_NAME>,<MAX_SIZE>,<ACTION>
<NAME> attribute specifies the name of the output channel.
<FILE_NAME> attribute specifies the name of the output file.
<MAX_SIZE> attribute represents the maximum size the specified file (in <FILE_NAME>) can grow to. This value is specified in bytes.
<ACTION> attribute specifies the action that is taken when the maximum size, defined in <MAX_SIZE>, is hit.
$outchannel directive and then used in a rule which selects every syslog message with any priority and executes the previously-defined output channel on the acquired syslog messages. Once the limit (in the example 100 MB) is hit, the /home/joe/log_rotation_script is executed. This script can contain anything from moving the file into a different folder, editing specific content out of it, or simply removing it.
$outchannel log_rotation,/var/log/test_log.log, 104857600, /home/joe/log_rotation_script *.* $log_rotation
,). To send messages to every user that is currently logged on, use an asterisk (*).
system() call to execute the program in shell. To specify a program to be executed, prefix it with a caret character (^). Consequently, specify a template that formats the received message and passes it to the specified executable as a one line parameter (for more information on templates, refer to Section 19.1.3.3, “Templates”). In the following example, any syslog message with any priority is selected, formatted with the template template and passed as a parameter to the test-program program, which is then executed with the provided parameter:
*.* ^test-program;template
:<PLUGIN>:<DB_HOST>,<DB_NAME>,<DB_USER>,<DB_PASSWORD>;[<TEMPLATE>]
<PLUGIN> calls the specified plug-in that handles the database writing (for example, the ommysql plug-in).
<DB_HOST> attribute specifies the database hostname.
<DB_NAME> attribute specifies the name of the database.
<DB_USER> attribute specifies the database user.
<DB_PASSWORD> attribute specifies the password used with the aforementioned database user.
<TEMPLATE> attribute specifies an optional use of a template that modifies the syslog message. For more information on templates, refer to Section 19.1.3.3, “Templates”.
MySQL (for more information, refer to /usr/share/doc/rsyslog-<version-number>/rsyslog_mysql.html) and PostgreSQL databases only. In order to use the MySQL and PostgreSQL database writer functionality, install the rsyslog-mysql and rsyslog-pgsql packages installed, respectively. Also, make sure you load the appropriate modules in your /etc/rsyslog.conf configuration file:
$ModLoad ommysql # Output module for MySQL support $ModLoad ompgsql # Output module for PostgreSQL support
omlibdb module. However, this module is currently not compiled.
~). The following rule discards any cron syslog messages:
cron.* ~
kern.=crit joe & ^test-program;temp & @192.168.0.1
crit) are send to user joe, processed by the template temp and passed on to the test-program executable, and forwarded to 192.168.0.1 via the UDP protocol.
;) and specify the name of the template.
$template<TEMPLATE_NAME>,"text %<PROPERTY>% more text", [<OPTION>]
$template is the template directive that indicates that the text following it, defines a template.
<TEMPLATE_NAME> is the name of the template. Use this name to refer to the template.
"…") is the actual template text. Within this text, you are allowed to escape characters in order to use their functionality, such as \n for new line or \r for carriage return. Other characters, such as % or ", have to be escaped in case you want to those characters literally.
%) specifies a property that is consequently replaced with the property's actual value. For more information on properties, refer to Section 19.1.3.3.2, “Properties”
<OPTION> attribute specifies any options that modify the template functionality. Do not mistake these for property options, which are defined inside the template text (between "…"). The currently supported template options are sql and stdsql used for formatting the text as an SQL query.
sql and stdsql options are specified in the template. If they are not, the database writer does not perform any action. This is to prevent any possible security threats, such as SQL injection.
timegenerated property to generate a unique file name for each syslog message:
$template DynamicFile,"/var/log/test_logs/%timegenerated%-test.log"
$template directive only specifies the template. You must use it inside a rule for it to take effect:
*.* ?DynamicFile
%)) allow you to access various contents of a syslog message through the use of a property replacer. To define a property inside a template (between the two quotation marks ("…")), use the following syntax:
%<PROPERTY_NAME>[:<FROM_CHAR>:<TO_CHAR>:<OPTION>]%
<PROPERTY_NAME> attribute specifies the name of a property. A comprehensible list of all available properties and their detailed description can be found in /usr/share/doc/rsyslog-<version-number>/property_replacer.html under the section Available Properties.
<FROM_CHAR> and <TO_CHAR> attributes denote a range of characters that the specified property will act upon. Alternatively, regular expressions can be used to specify a range of characters. To do so, specify the letter R as the <FROM_CHAR> attribute and specify your desired regular expression as the <TO_CHAR> attribute.
<OPTION> attribute specifies any property options. A comprehensible list of all available properties and their detailed description can be found in /usr/share/doc/rsyslog-<version-number>/property_replacer.html under the section Property Options.
%msg%
%msg:1:2%
%msg:::drop-last-lf%
%timegenerated:1:10:date-rfc3339%
$template verbose,"%syslogseverity%,%syslogfacility%,%timegenerated%,%HOSTNAME%,%syslogtag%,%msg%\n"
mesg(1) permission set to yes). This template outputs the message text, along with a hostname, message tag and a timestamp, on a new line (using \r and \n) and rings the bell (using \7).
$template wallmsg,"\r\n\7Message from syslogd@%HOSTNAME% at %timegenerated% ...\r\n %syslogtag% %msg%\n\r"
sql option at the end of the template specified as the template option. It tells the database writer to format the message as an MySQL SQL query.
$template dbFormat,"insert into SystemEvents (Message, Facility,FromHost, Priority, DeviceReportedTime, ReceivedAt, InfoUnitID, SysLogTag) values ('%msg%', %syslogfacility%, '%HOSTNAME%',%syslogpriority%, '%timereported:::date-mysql%', '%timegenerated:::date-mysql%', %iut%, '%syslogtag%')",sqlRSYSLOG_ prefix. It is advisable to not create a template using this prefix to avoid any conflicts. The following list shows these predefined templates along with their definitions.
RSYSLOG_DebugFormat"Debug line with all properties:\nFROMHOST: '%FROMHOST%', fromhost-ip: '%fromhost-ip%', HOSTNAME: '%HOSTNAME%', PRI: %PRI%,\nsyslogtag '%syslogtag%', programname: '%programname%', APP-NAME: '%APP-NAME%', PROCID: '%PROCID%', MSGID: '%MSGID%',\nTIMESTAMP: '%TIMESTAMP%', STRUCTURED-DATA: '%STRUCTURED-DATA%',\nmsg: '%msg%'\nescaped msg: '%msg:::drop-cc%'\nrawmsg: '%rawmsg%'\n\n\"
RSYSLOG_SyslogProtocol23Format"<%PRI%>1 %TIMESTAMP:::date-rfc3339% %HOSTNAME% %APP-NAME% %PROCID% %MSGID% %STRUCTURED-DATA% %msg%\n\"
RSYSLOG_FileFormat"%TIMESTAMP:::date-rfc3339% %HOSTNAME% %syslogtag%%msg:::sp-if-no-1st-sp%%msg:::drop-last-lf%\n\"
RSYSLOG_TraditionalFileFormat"%TIMESTAMP% %HOSTNAME% %syslogtag%%msg:::sp-if-no-1st-sp%%msg:::drop-last-lf%\n\"
RSYSLOG_ForwardFormat"<%PRI%>%TIMESTAMP:::date-rfc3339% %HOSTNAME% %syslogtag:1:32%%msg:::sp-if-no-1st-sp%%msg%\"
RSYSLOG_TraditionalForwardFormat"<%PRI%>%TIMESTAMP% %HOSTNAME% %syslogtag:1:32%%msg:::sp-if-no-1st-sp%%msg%\"
-c option. When no parameter is specified, rsyslog tries to be compatible with sysklogd. This is partially achieved by activating configuration directives that modify your configuration accordingly. Therefore, it is advisable to supply this option with a number that matches the major version of rsyslog that is in use and update your /etc/rsyslog.conf configuration file accordingly. If you want to, for example, use sysklogd options (which were deprecated in version 3 of rsyslog), you can specify so by executing the following command:
~]# rsyslogd -c 2
rsyslogd daemon, including the backward compatibility mode, can be specified in the /etc/sysconfig/rsyslog configuration file.
rsyslogd options, refer to man rsyslogd.
/var/log/ directory. Some applications such as httpd and samba have a directory within /var/log/ for their log files.
/var/log/ directory with numbers after them (for example, cron-20100906). These numbers represent a timestamp that has been added to a rotated log file. Log files are rotated so their file sizes do not become too large. The logrotate package contains a cron task that automatically rotates log files according to the /etc/logrotate.conf configuration file and the configuration files in the /etc/logrotate.d/ directory.
/etc/logrotate.conf configuration file:
# rotate log files weekly weekly # keep 4 weeks worth of backlogs rotate 4 # uncomment this if you want your log files compressed compress
.gz format. Any lines that begin with a hash sign (#) are comments and are not processed
/etc/logrotate.d/ directory and define any configuration options there.
/etc/logrotate.d/ directory:
/var/log/messages {
rotate 5
weekly
postrotate
/usr/bin/killall -HUP syslogd
endscript
}
/var/log/messages log file only. The settings specified here override the global settings where possible. Thus the rotated /var/log/messages log file will be kept for five weeks instead of four weeks as was defined in the global options.
weekly — Specifies the rotation of log files on a weekly basis. Similar directives include:
daily
monthly
yearly
compress — Enables compression of rotated log files. Similar directives include:
nocompress
compresscmd — Specifies the command to be used for compressing.
uncompresscmd
compressext — Specifies what extension is to be used for compressing.
compressoptions — Lets you specify any options that may be passed to the used compression program.
delaycompress — Postpones the compression of log files to the next rotation of log files.
rotate <INTEGER> — Specifies the number of rotations a log file undergoes before it is removed or mailed to a specific address. If the value 0 is specified, old log files are removed instead of rotated.
mail <ADDRESS> — This option enables mailing of log files that have been rotated as many times as is defined by the rotate directive to the specified address. Similar directives include:
nomail
mailfirst — Specifies that the just-rotated log files are to be mailed, instead of the about-to-expire log files.
maillast — Specifies that the about-to-expire log files are to be mailed, instead of the just-rotated log files. This is the default option when mail is enabled.
logrotate man page (man logrotate).
Vi or Emacs. Some log files are readable by all users on the system; however, root privileges are required to read most log files.
~]# yum install gnome-system-log~]$ gnome-system-log
.gz format.
rsyslogd manual page — Type man rsyslogd to learn more about rsyslogd and its many options.
rsyslog.conf manual page — Type man rsyslog.conf to learn more about the /etc/rsyslog.conf configuration file and its many options.
/usr/share/doc/rsyslog-<version-number>/ — After installing the rsyslog package, this directory contains extensive documentation in the html format.
logrotate manual page — Type man logrotate to learn more about logrotate and its many options.
/etc/rsyslog.conf configuration examples.
locate command is updated daily. A system administrator can use automated tasks to perform periodic backups, monitor the system, run custom scripts, and more.
cron, at, and batch.
cronie RPM package must be installed and the crond service must be running. anacron is a sub-package of cronie. To determine if these packages are installed, use the rpm -q cronie cronie-anacron command.
/sbin/service crond status. To start the cron service, use the command /sbin/service crond start. To stop the service, use the command /sbin/service crond stop. It is recommended that you start the service at boot time. Refer to Chapter 9, Services and Daemons for details on starting the cron service automatically at boot time.
/etc/anacrontab (only root is allowed to modify this file), which contains the following lines:
SHELL=/bin/sh PATH=/sbin:/bin:/usr/sbin:/usr/bin MAILTO=root # the maximal random delay added to the base delay of the jobs RANDOM_DELAY=45 # the jobs will be started during the following hours only START_HOURS_RANGE=3-22 #period in days delay in minutes job-identifier command 1 5 cron.daily nice run-parts /etc/cron.daily 7 25 cron.weekly nice run-parts /etc/cron.weekly @monthly 45 cron.monthly nice run-parts /etc/cron.monthly
SHELL variable tells the system which shell environment to use (in this example the bash shell). The PATH variable defines the path used to execute commands. The output of the anacron jobs are emailed to the username defined with the MAILTO variable. If the MAILTO variable is not defined, (i.e. is empty, MAILTO=), email is not sent.
RANDOM_DELAY variable denotes the maximum number of minutes that will be added to the delay in minutes variable which is specified for each job. The minimum delay value is set, by default, to 6 minutes. A RANDOM_DELAY set to 12 would therefore add, randomly, between 6 and 12 minutes to the delay in minutes for each job in that particular anacrontab. RANDOM_DELAY can also be set to a value below 6, or even 0. When set to 0, no random delay is added. This proves to be useful when, for example, more computers that share one network connection need to download the same data every day. The START_HOURS_RANGE variable defines an interval (in hours) when scheduled jobs can be run. In case this time interval is missed, for example, due to a power down, then scheduled jobs are not executed that day.
/etc/anacrontab file represent scheduled jobs and have the following format:
period in days delay in minutes job-identifier command
period in days — specifies the frequency of execution of a job in days. This variable can be represented by an integer or a macro (@daily, @weekly, @monthly), where @daily denotes the same value as the integer 1, @weekly the same as 7, and @monthly specifies that the job is run once a month, independent on the length of the month.
delay in minutes — specifies the number of minutes anacron waits, if necessary, before executing a job. This variable is represented by an integer where 0 means no delay.
job-identifier — specifies a unique name of a job which is used in the log files.
command — specifies the command to execute. The command can either be a command such as ls /proc >> /tmp/proc or a command to execute a custom script.
/etc/anacrontab file:
SHELL=/bin/sh PATH=/sbin:/bin:/usr/sbin:/usr/bin MAILTO=root # the maximal random delay added to the base delay of the jobs RANDOM_DELAY=30 # the jobs will be started during the following hours only START_HOURS_RANGE=16-20 #period in days delay in minutes job-identifier command 1 20 dailyjob nice run-parts /etc/cron.daily 7 25 weeklyjob /etc/weeklyjob.bash @monthly 45 monthlyjob ls /proc >> /tmp/proc
anacrontab file are randomly delayed by 6-30 minutes and can be executed between 16:00 and 20:00. Thus, the first defined job will run anywhere between 16:26 and 16:50 every day. The command specified for this job will execute all present programs in the /etc/cron.daily directory (using the run-parts script which takes a directory as a command-line argument and sequentially executes every program within that directory). The second specified job will be executed once a week and will execute the weeklyjob.bash script in the /etc directory. The third job is executed once a month and runs a command to write the contents of the /proc to the /tmp/proc file (e.g. ls /proc >> /tmp/proc).
cronie-anacron package. Thus, you will be able to define jobs using crontabs only.
/etc/crontab (only root is allowed to modify this file), contains the following lines:
SHELL=/bin/bash PATH=/sbin:/bin:/usr/sbin:/usr/bin MAILTO=root HOME=/ # For details see man 4 crontabs # Example of job definition: # .---------------- minute (0 - 59) # | .------------- hour (0 - 23) # | | .---------- day of month (1 - 31) # | | | .------- month (1 - 12) OR jan,feb,mar,apr ... # | | | | .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat # | | | | | # * * * * * user command to be executed
anacrontab file, SHELL, PATH and MAILTO. For more information about these variables, refer to Section 20.1.2, “Configuring Anacron Jobs”. The fourth line contains the HOME variable. The HOME variable can be used to set the home directory to use when executing commands or scripts.
/etc/crontab file represent scheduled jobs and have the following format:
minute hour day month day of week user command
minute — any integer from 0 to 59
hour — any integer from 0 to 23
day — any integer from 1 to 31 (must be a valid day if a month is specified)
month — any integer from 1 to 12 (or the short name of the month such as jan or feb)
day of week — any integer from 0 to 7, where 0 or 7 represents Sunday (or the short name of the week such as sun or mon)
user — specifies the user under which the jobs are run
command — the command to execute (the command can either be a command such as ls /proc >> /tmp/proc or the command to execute a custom script)
1-4 means the integers 1, 2, 3, and 4.
3, 4, 6, 8 indicates those four specific integers.
/<integer>. For example, 0-59/2 can be used to define every other minute in the minute field. Step values can also be used with an asterisk. For instance, the value */3 can be used in the month field to run the task every third month.
crontab utility. All user-defined crontabs are stored in the /var/spool/cron/ directory and are executed using the usernames of the users that created them. To create a crontab as a user, login as that user and type the command crontab -e to edit the user's crontab using the editor specified by the VISUAL or EDITOR environment variable. The file uses the same format as /etc/crontab. When the changes to the crontab are saved, the crontab is stored according to username and written to the file /var/spool/cron/username. To list the contents of your own personal crontab file, use the crontab -l command.
crontab utility, there is no need to specify a user when defining a job.
/etc/cron.d/ directory contains files that have the same syntax as the /etc/crontab file. Only root is allowed to create and modify files in this directory.
/etc/anacrontab file, the /etc/crontab file, the /etc/cron.d/ directory, and the /var/spool/cron/ directory every minute for any changes. If any changes are found, they are loaded into memory. Thus, the daemon does not need to be restarted if an anacrontab or a crontab file is changed.
/etc/cron.allow and /etc/cron.deny files are used to restrict access to cron. The format of both access control files is one username on each line. Whitespace is not permitted in either file. The cron daemon (crond) does not have to be restarted if the access control files are modified. The access control files are checked each time a user tries to add or delete a cron job.
cron.allow exists, only users listed in it are allowed to use cron, and the cron.deny file is ignored.
cron.allow does not exist, users listed in cron.deny are not allowed to use cron.
/etc/security/access.conf. For example, adding the following line in this file forbids creating crontabs for all users except the root user:
-:ALL EXCEPT root :cron
access.conf.5 (i.e. man 5 access.conf).
run-parts script on a cron folder, such as /etc/cron.daily, we can define which of the programs in this folder will not be executed by run-parts.
jobs.deny file in the folder that run-parts will be executing from. For example, if we need to omit a particular program from /etc/cron.daily, then, a file /etc/cron.daily/jobs.deny has to be created. In this file, specify the names of the omitted programs from the same directory. These will not be executed when a command, such as run-parts /etc/cron.daily, is executed by a specific job.
jobs.allow file.
jobs.deny and jobs.allow are the same as those of cron.deny and cron.allow described in section Section 20.1.4, “Controlling Access to Cron”.
at command is used to schedule a one-time task at a specific time and the batch command is used to schedule a one-time task to be executed when the systems load average drops below 0.8.
at or batch, the at RPM package must be installed, and the atd service must be running. To determine if the package is installed, use the rpm -q at command. To determine if the service is running, use the command /sbin/service atd status.
at time, where timetime can be one of the following:
/usr/share/doc/at-<version>/timespec text file.
at command with the time argument, the at> prompt is displayed. Type the command to execute, press Enter, and press Ctrl+D. Multiple commands can be specified by typing each command followed by the Enter key. After typing all the commands, press Enter to go to a blank line and press Ctrl+D. Alternatively, a shell script can be entered at the prompt, pressing Enter after each line in the script, and pressing Ctrl+D on a blank line to exit. If a script is entered, the shell used is the shell set in the user's SHELL environment, the user's login shell, or /bin/sh (whichever is found first).
atq to view pending jobs. Refer to Section 20.2.3, “Viewing Pending Jobs” for more information.
at command can be restricted. For more information, refer to Section 20.2.5, “Controlling Access to At and Batch” for details.
batch command.
batch command, the at> prompt is displayed. Type the command to execute, press Enter, and press Ctrl+D. Multiple commands can be specified by typing each command followed by the Enter key. After typing all the commands, press Enter to go to a blank line and press Ctrl+D. Alternatively, a shell script can be entered at the prompt, pressing Enter after each line in the script, and pressing Ctrl+D on a blank line to exit. If a script is entered, the shell used is the shell set in the user's SHELL environment, the user's login shell, or /bin/sh (whichever is found first). As soon as the load average is below 0.8, the set of commands or script is executed.
atq to view pending jobs. Refer to Section 20.2.3, “Viewing Pending Jobs” for more information.
batch command can be restricted. For more information, refer to Section 20.2.5, “Controlling Access to At and Batch” for details.
at and batch jobs, use the atq command. The atq command displays a list of pending jobs, with each job on a line. Each line follows the job number, date, hour, job class, and username format. Users can only view their own jobs. If the root user executes the atq command, all jobs for all users are displayed.
at and batch include:
at and batch Command Line Options| Option | Description |
|---|---|
-f
| Read the commands or shell script from a file instead of specifying them at the prompt. |
-m
| Send email to the user when the job has been completed. |
-v
| Display the time that the job is executed. |
/etc/at.allow and /etc/at.deny files can be used to restrict access to the at and batch commands. The format of both access control files is one username on each line. Whitespace is not permitted in either file. The at daemon (atd) does not have to be restarted if the access control files are modified. The access control files are read each time a user tries to execute the at or batch commands.
at and batch commands, regardless of the access control files.
at.allow exists, only users listed in it are allowed to use at or batch, and the at.deny file is ignored.
at.allow does not exist, users listed in at.deny are not allowed to use at or batch.
at service, use the command /sbin/service atd start. To stop the service, use the command /sbin/service atd stop. It is recommended that you start the service at boot time. Refer to Chapter 9, Services and Daemons for details on starting the cron service automatically at boot time.
cron man page — contains an overview of cron.
crontab man pages in sections 1 and 5 — The man page in section 1 contains an overview of the crontab file. The man page in section 5 contains the format for the file and some example entries.
anacron man page — contains an overview of anacron.
anacrontab man page — contains an overview of the anacrontab file.
/usr/share/doc/at-<version>/timespec contains more detailed information about the times that can be specified for cron jobs.
at man page — description of at and batch and their command line options.
abrtd, which runs silently in the background most of the time. It springs into action when an application crashes, or a kernel oops is detected. The daemon then collects the relevant problem data such as a core file if there is one, the crashing application's command line parameters, and other data of forensic utility.
FTP/SCP, email it, or write it to a file.
abrtd — The ABRT daemon which runs under root as a background service.
abrt-ccpp — The ABRT service that provides the C/C++ problems analyzer
abrt-oops — The ABRT service that provides the kernel oopses analyzer.
~]# yum install abrt-desktop~]# yum install abrt-cliabrtd is running. The daemon is typically configured to start up at boot time. You can use the following command as root to verify its current status:
~]# service abrtd status
abrtd (pid 1535) is running...service command returns the abrt is stopped message, the daemon is not running. It can be started for the current session by entering this command:
~]# service abrtd start
Starting abrt daemon: [ OK ]chkconfig command to ensure that the abrtd service initializes every time the system starts up:
~]# chkconfig abrtd onabrt-ccpp service if you want ABRT to catch C/C++ crashes. To set ABRT to detect kernel oopses, use the same steps for the abrt-oops service. Note that this service cannot catch kernel oopses which cause the system to fail to become unresponsive or to reboot immediately.
ABRT notification applet is running:
~]$ ps -el | grep abrt-applet
0 S 500 2036 1824 0 80 0 - 61604 poll_s ? 00:00:00 abrt-appletabrt-applet program:
~]$ abrt-applet &
[1] 2261
analyzer
architecture
coredump
cmdline
executable
kernel
os_release
reason
time
uid
backtrace, can be created during analysis depending on which analyzer method is used and its configuration settings. Each of these files holds specific information about the system and the problem itself. For example, the kernel file records the version of the crashed kernel.
~]$ abrt-gui &
abrtd can be viewed, reported, and deleted using the command line interface.
abrt-cli[--version]<command>[<args>]
<args> stands for a problem data directory and/or options modifying the commands, and <command> is one of the following sub-commands:
list — lists problems and views the problem data.
report — analyzes and reports problems.
rm — removes unneeded problems.
info — provides information about a particular problem.
abrt-cli command use:
abrt-cli <command> --help abrt-cli list command:
~]# abrt-cli list
Directory: /var/spool/abrt/ccpp-2011-09-13-10:18:14-2895
count: 2
executable: /usr/bin/gdb
package: gdb-7.2-48.el6
time: Tue 13 Sep 2011 10:18:14 AM CEST
uid: 500
Directory: /var/spool/abrt/ccpp-2011-09-21-18:18:07-2841
count: 1
executable: /bin/bash
package: bash-4.1.2-8.el6
time: Wed 21 Sep 2011 06:18:07 PM CEST
uid: 500Directory — Shows the problem data directory that contains all information about the problem.
count — Shows how many times this particular problem occurred.
executable — Indicates which binary or executable script crashed.
package — Shows the name of the package that contains the program that caused the problem.
time — Shows the date and time of the last occurrence of the problem.
uid — Shows the ID of the user which ran the program that crashed.
abrt-cli list command. All options are mutually inclusive so you can combine them according to your need. The command output will be the most comprehensive if you combine all options, and you will receive the least details if you use no additional options.
abrt-cli list command options| Option | Description |
|---|---|
With no additional option, the abrt-cli list command displays only basic information for problems that have not been reported yet.
| |
-d, --detailed
|
Displays all stored information about problems listed, including a backtrace if it has already been generated.
|
-f, --full
| Displays basic information for all problems including the already-reported ones. |
-v, --verbose
| Provides additional information on its actions. |
abrt-cli info<DIR>
<DIR> stands for the problem data directory of the problem that is being viewed. The following table shows options available with the abrt-cli info command. All options are mutually inclusive so you can combine them according to your need. The command output will be the most comprehensive if you combine all options, and you will receive the least details if you use no additional options.
abrt-cli info command options| Option | Description |
|---|---|
With no additional option, the abrt-cli info command displays only basic information for the problem specified by the problem data directory argument.
| |
-d, --detailed
|
Displays all stored information for the problem specified by the problem data directory argument, including a backtrace if it has already been generated.
|
-v, --verbose
|
abrt-cli info provides additional information on its actions.
|
abrt-cli report <DIR> <DIR> stands for the problem data directory of the problem that is being reported. For example:
~]$abrt-cli report/var/spool/abrt/ccpp-2011-09-13-10:18:14-2895How you would like to analyze the problem? 1) Collect .xsession-errors 2) Local GNU Debugger Select analyzer: _
abrt-cli opens a text editor with the content of the report. You can see what is being reported, and you can fill in instructions on how to reproduce the crash and other comments. You should also check the backtrace, because the backtrace might be sent to a public server and viewed by anyone, depending on the problem reporter event settings.
abrt-cli uses the editor defined in the ABRT_EDITOR environment variable. If the variable is not defined, it checks the VISUAL and EDITOR variables. If none of these variables is set, vi is used. You can set the preferred editor in your .bashrc configuration file. For example, if you prefer GNU Emacs, add the following line to the file:
exportVISUAL=emacs
How would you like to report the problem? 1) Logger 2) Red Hat Customer Support Select reporter(s): _
abrt-cli report command.
abrt-cli report command options| Option | Description |
|---|---|
With no additional option, the abrt-cli report provides the usual output.
| |
-v, --verbose
|
abrt-cli report provides additional information on its actions.
|
abrt-cli rm <DIR> <DIR> stands for the problem data directory of the problem being deleted. For example:
~]$abrt-cli rm/var/spool/abrt/ccpp-2011-09-12-18:37:24-4413rm '/var/spool/abrt/ccpp-2011-09-12-18:37:24-4413'
abrt-cli rm command.
abrt-cli rm command options| Option | Description |
|---|---|
With no additional option, the abrt-cli rm.
| |
-v, --verbose
|
abrt-cli rm provides additional information on its actions.
|
/etc/libreport/ — contains the report_event.conf main configuration file. More information about this configuration file can be found in Section 21.4.1, “ABRT Events”.
/etc/libreport/events/ — holds files specifying the default setting of predefined events.
/etc/libreport/events.d/ — keeps configuration files defining events.
/etc/libreport/plugins/ — contains configuration files of programs that take part in events.
/etc/abrt/ — holds ABRT specific configuration files used to modify the behavior of ABRT's services and programs. More information about certain specific configuration files can be found in Section 21.4.4, “ABRT Specific Configuration”.
/etc/abrt/plugins/ — keeps configuration files used to override the default setting of ABRT's services and programs. For more information on some specific configuration files refer to Section 21.4.4, “ABRT Specific Configuration”.
/etc/libreport/events.d/ directory. These configuration files are used by the main configuration file, /etc/libreport/report_event.conf.
/etc/libreport/report_event.conf file consists of include directives and rules. Rules are typically stored in other configuration files in the /etc/libreport/events.d/ directory. In the standard installation, the /etc/libreport/report_event.conf file contains only one include directive:
include events.d/*.confspace character or the tab character are considered a part of this rule. Each rule consists of two parts, a condition part and a program part. The condition part contains conditions in one of the following forms:
VAR=VAL,
VAR!=VAL, or
VAL~=REGEX
VAR is either the EVENT key word or a name of a problem data directory element (such as executable, package, hostname, etc.),
VAL is either a name of an event or a problem data element, and
REGEX is a regular expression.
EVENT=post-create date > /tmp/dt echo $HOSTNAME `uname -r`
/tmp/dt file with the current date and time, and print the hostname of the machine and its kernel version on the standard output.
~/.xsession-errors file to the problem report for any problem for which the abrt-ccpp services has been used to process that problem, and the crashed application has loaded any X11 libraries at the time of crash:
EVENT=analyze_xsession_errors analyzer=CCpp dso_list~=.*/libX11.* test -f ~/.xsession-errors || { echo "No ~/.xsession-errors"; exit 1; } test -r ~/.xsession-errors || { echo "Can't read ~/.xsession-errors"; exit 1; } executable=`cat executable` && base_executable=${executable##*/} && grep -F -e "$base_executable" ~/.xsession-errors | tail -999 >xsession_errors && echo "Element 'xsession_errors' saved"
post-create abrtd on newly created problem data directories. When the post-create event is run, abrtd checks whether the UUID identifier of the new problem data matches the UUID of any already existing problem directories. If such a problem directory exists, the new problem data is deleted.
analyze_<NAME_SUFFIX> <NAME_SUFFIX> is the adjustable part of the event name. This event is used to process collected data. For example, the analyze_LocalGDB runs the GNU Debugger (GDB) utility on a core dump of an application and produces a backtrace of a program. You can view the list of analyze events and choose from it using abrt-gui.
collect_<NAME_SUFFIX> <NAME_SUFFIX> is the adjustable part of the event name. This event is used to collect additional information on a problem. You can view the list of collect events and choose from it using abrt-gui.
report_<NAME_SUFFIX> <NAME_SUFFIX> is the adjustable part of the event name. This event is used to report a problem. You can view the list of report events and choose from it using abrt-gui.
/etc/libreport/events/<event_name>.xml files. These files are used by abrt-gui and abrt-cli to make the user interface more friendly. Do not edit these files unless you want to modify the standard installation.
analyze_xsession_errors event is shown as Collect .xsession-errors in ABRT GUI. The following is a list of default analyzing, collecting and reporting events provided by the standard installation of ABRT:
backtrace of a program. It is defined in the /etc/libreport/events.d/ccpp_event.conf configuration file.
~/.xsession-errors file to the problem report. It is defined in the /etc/libreport/events.d/ccpp_event.conf configuration file.
/etc/libreport/events.d/print_event.conf configuration file.
/etc/libreport/events.d/rhtsupport_event.conf configuration file.
/etc/libreport/events.d/mailx_event.conf configuration file.
/etc/libreport/events.d/koops_event.conf configuration file.
FTP or the SCP protocol. It is defined in the /etc/libreport/events.d/uploader_event.conf configuration file.
report_Logger event accepts an output file name as a parameter). Using the respective /etc/libreport/events/<event_name>.xml file, ABRT GUI determines which parameters can be specified for a selected event and allows a user to set the values for these parameters. These values are saved by ABRT GUI and reused on subsequent invocations of these events.
/etc/libreport/ directory hierarchy are world readable and are meant to be used as global settings. Thus, it is not advisable to store usernames, passwords or any other sensitive data in them. The per-user settings (set in the GUI application and readable by the owner of $HOME only) are stored in the Gnome keyring or can be stored in a text file in $HOME/.abrt/*.conf for use in abrt-cli.
/var/log/abrt.log).
SSL protocol is used when sending the data over the network.
Subject field of a problem report email sent by Mailx (by default, set to "[abrt] detected a crash").
From field of a problem report email.
FTP or SCP protocol (by default, set to ftp://localhost:/tmp/upload).
/etc/abrt/abrt.conf — allows you to modify the behavior of the abrtd service.
/etc/abrt/abrt-action-save-package-data.conf — allows you to modify the behavior of the abrt-action-save-package-data program.
/etc/abrt/plugins/CCpp.conf — allows you to modify the behavior of ABRT's core catching hook.
/etc/abrt/abrt.conf file:
abrtd to auto-unpack crashdump tarball archives (.tar.gz) which are located in the specified directory. In the example above, it is the /var/spool/abrt-upload/ directory. Whichever directory you specify in this directive, you must ensure that it exists and it is writable for abrtd. The ABRT daemon will not create it automatically.
abrt_selinux(8) manual page for more information on running ABRT in SELinux.
setsebool -P abrt_anon_write 1 <size_in_megabytes> 1000 MB. Once the quota specified here has been met, ABRT will continue catching problems, and in order to make room for the new crash dumps, it will delete the oldest and largest ones.
/var/spool/abrt directory. Whichever directory you specify in this directive, you must ensure that it exists and it is writable for abrtd.
abrt_selinux(8) manual page for more information on running ABRT in SELinux.
setsebool -P abrt_anon_write 1 /etc/abrt/abrt-action-save-package-data.conf file:
<yes/no> OpenGPGCheck directive to yes (the default setting) tells ABRT to only analyze and handle crashes in applications provided by packages which are signed by the GPG keys whose locations are listed in the /etc/abrt/gpg_keys file. Setting OpenGPGCheck to no tells ABRT to catch crashes in all programs.
<MORE_PACKAGES> ] BlackList directive will not be handled by ABRT. If you want ABRT to ignore other packages and binaries, list them here separated by commas.
<yes/no> /usr/share/doc/*, */example* /etc/abrt/plugins/CCpp.conf file:
<yes/no> ulimit -c setting allows it. The directive is set to yes by default.
<yes/no> EVENT=report_Bugzilla condition with the EVENT=port-create condition in the /etc/libreport/events.d/python_event.conf file:
EVENT=post-create analyzer=Python test -f component || abrt-action-save-package-data reporter-bugzilla -c /etc/abrt/plugins/Bugzilla.conf
post-create runs with root privilegespost-create event is run by abrtd, which usually runs with root privileges.
http_proxy and the ftp_proxy environment variables. When you use environment variables as a part of a reporting event, they inherit their values from the process which performs reporting, usually abrt-gui or abrt-cli. Therefore, you can specify HTTP or FTP proxy servers by using these variables in your working environment.
post-create event, they will run as children of the abrtd process. You should either adjust the environment of abrtd or modify the rules to set these variables. For example:
EVENT=post-create analyzer=Python test -f component || abrt-action-save-package-data export http_proxy=http://proxy.server:8888/ reporter-bugzilla -c /etc/abrt/plugins/Bugzilla.conf
yum install libreport-plugin-reportuploader). See the following sections on how to configure systems to use ABRT's centralized crash collection.
/var/spool/abrt-upload/ is used (the rest of the document assumes you are using this directory). Make sure this directory is writable by the abrt user.
abrt. This user is used by the abrtd daemon, for example, as the owner:group of /var/spool/abrt/* directories.
/etc/abrt/abrt.conf configuration file, set the WatchCrashdumpArchiveDir directive to the following:
WatchCrashdumpArchiveDir = /var/spool/abrt-upload/
FTP or SCP. For more information on how to configure FTP, refer to Section 17.2, “FTP”. For more information on how to configure SCP, refer to Section 11.3.2, “Using the scp Utility”.
FTP, upload a file using an interactive FTP client:
~]$ftpftp>open SERVERNAMEName:USERNAMEPassword:PASSWORDftp>cd /var/spool/abrt-upload250 Operation successful ftp>put TESTFILEftp>quit
TESTFILE appeared in the correct directory on the server system.
MaxCrashReportsSize directive (in the /etc/abrt/abrt.conf configuration file) needs to be set to a larger value if the expected volume of crash data is larger than the default 1000 MB.
/etc/libreport/events.d/ccpp_events.conf configuration file:
EVENT=analyze_LocalGDB analyzer=CCpp abrt-action-analyze-core.py --core=coredump -o build_ids && abrt-action-install-debuginfo-to-abrt-cache --size_mb=4096 && abrt-action-generate-backtrace && abrt-action-analyze-backtrace
remote!=1 condition to the rule.
package and the component elements) in the problem data. Refer to Section 21.5.3, “Saving Package Information” to find out whether you need to collect package information in your centralized crash collection configuration and how to configure it properly.
/etc/libreport/events.d/ccpp_events.conf file. Refer to Section 21.5.1, “Configuration Steps Required on a Dedicated System” for an example of such a example.
/etc/libreport/events.d/abrt_event.conf file. Refer to Section 21.5.3, “Saving Package Information” to find out whether you need to collect package information in your centralized crash collection configuration and how to configure it properly.
/etc/libreport/events.d/abrt_event.conf configuration file:
report_SFX event if you want to store problem data locally on clients and upload it later using ABRT GUI/CLI. The following is an example of such an event:
post-create event runs the abrt-action-save-package-data tool (among other steps) in order to provide this information in the standard ABRT installation.
/etc/libreport/events.d/abrt_event.conf file:
/etc/abrt/abrt-action-save-package-data.conf file:
ProcessUnpackaged = yes
remote!=1 condition in the /etc/libreport/events.d/abrt_event.conf file:
/etc/abrt/abrt-action-save-package-data.conf:
ProcessUnpackaged = yes
kill -s SEGV PID command to terminate a process on a client system. For example, start a sleep process and terminate it with the kill command in the following way:
~]$sleep 100 &[1] 2823 ~]$kill -s SEGV 2823
kill command. Check that the crash was detected by ABRT on the client system (this can be checked by examining the appropriate syslog file, by running the abrt-cli list --full command, or by examining the crash dump created in the /var/spool/abrt directory), copied to the server system, unpacked on the server system and can be seen and acted upon using abrt-cli or abrt-gui on the server system.
oprofile package must be installed to use this tool.
--separate=library option is used.
opreport does not associate samples for inline functions properly — opreport uses a simple address range mechanism to determine which function an address is in. Inline function samples are not attributed to the inline function but rather to the function the inline function was inserted into.
opcontrol --reset to clear out the samples from previous runs.
timer mode. Run the command opcontrol --deinit, and then execute modprobe oprofile timer=1 to enable the timer mode.
oprofile package.
| Command | Description |
|---|---|
ophelp
|
Displays available events for the system's processor along with a brief description of each.
|
opimport
|
Converts sample database files from a foreign binary format to the native format for the system. Only use this option when analyzing a sample database from a different architecture.
|
opannotate
|
Creates annotated source for an executable if the application was compiled with debugging symbols. Refer to Section 22.5.4, “Using opannotate” for details.
|
opcontrol
|
Configures what data is collected. Refer to Section 22.2, “Configuring OProfile” for details.
|
opreport
|
Retrieves profile data. Refer to Section 22.5.1, “Using
opreport” for details.
|
oprofiled
|
Runs as a daemon to periodically write sample data to disk.
|
opcontrol utility to configure OProfile. As the opcontrol commands are executed, the setup options are saved to the /root/.oprofile/daemonrc file.
~]# opcontrol --setup --vmlinux=/usr/lib/debug/lib/modules/`uname -r`/vmlinux~]# opcontrol --setup --no-vmlinuxoprofile kernel module, if it is not already loaded, and creates the /dev/oprofile/ directory, if it does not already exist. Refer to Section 22.6, “Understanding /dev/oprofile/” for details about this directory.
| Processor |
cpu_type
| Number of Counters |
|---|---|---|
| AMD64 | x86-64/hammer | 4 |
| AMD Athlon | i386/athlon | 4 |
| AMD Family 10h | x86-64/family10 | 4 |
| AMD Family 11h | x86-64/family11 | 4 |
| AMD Family 12h | x86-64/family12 | 4 |
| AMD Family 14h | x86-64/family14 | 4 |
| AMD Family 15h | x86-64/family15 | 6 |
| IBM eServer System i and IBM eServer System p | timer | 1 |
| IBM POWER4 | ppc64/power4 | 8 |
| IBM POWER5 | ppc64/power5 | 6 |
| IBM PowerPC 970 | ppc64/970 | 8 |
| IBM S/390 and IBM System z | timer | 1 |
| Intel Core i7 | i386/core_i7 | 4 |
| Intel Nehalem microarchitecture | i386/nehalem | 4 |
| Intel Pentium 4 (non-hyper-threaded) | i386/p4 | 8 |
| Intel Pentium 4 (hyper-threaded) | i386/p4-ht | 4 |
| Intel Westmere microarchitecture | i386/westmere | 4 |
| TIMER_INT | timer | 1 |
timer is used as the processor type if the processor does not have supported performance monitoring hardware.
timer is used, events cannot be set for any processor because the hardware does not have support for hardware performance counters. Instead, the timer interrupt is used for profiling.
timer is not used as the processor type, the events monitored can be changed, and counter 0 for the processor is set to a time-based event by default. If more than one counter exists on the processor, the counters other than counter 0 are not set to an event by default. The default events monitored are shown in Table 22.3, “Default Events”.
| Processor | Default Event for Counter | Description |
|---|---|---|
| AMD Athlon and AMD64 | CPU_CLK_UNHALTED | The processor's clock is not halted |
| AMD Family 10h, AMD Family 11h, AMD Family 12h | CPU_CLK_UNHALTED | The processor's clock is not halted |
| AMD Family 14h, AMD Family 15h | CPU_CLK_UNHALTED | The processor's clock is not halted |
| IBM POWER4 | CYCLES | Processor Cycles |
| IBM POWER5 | CYCLES | Processor Cycles |
| IBM PowerPC 970 | CYCLES | Processor Cycles |
| Intel Core i7 | CPU_CLK_UNHALTED | The processor's clock is not halted |
| Intel Nehalem microarchitecture | CPU_CLK_UNHALTED | The processor's clock is not halted |
| Intel Pentium 4 (hyper-threaded and non-hyper-threaded) | GLOBAL_POWER_EVENTS | The time during which the processor is not stopped |
| Intel Westmere microarchitecture | CPU_CLK_UNHALTED | The processor's clock is not halted |
| TIMER_INT | (none) | Sample for each timer interrupt |
~]# ls -d /dev/oprofile/[0-9]*~]# ophelpopcontrol:
~]# opcontrol --event=event-name:sample-rateevent-name with the exact name of the event from ophelp, and replace sample-rate with the number of events between samples.
cpu_type is not timer, each event can have a sampling rate set for it. The sampling rate is the number of events between each sample snapshot.
~]# opcontrol --event=event-name:sample-ratesample-rate with the number of events to wait before sampling again. The smaller the count, the more frequent the samples. For events that do not happen frequently, a lower count may be needed to capture the event instances.
ophelp command. The values for each unit mask are listed in hexadecimal format. To specify more than one unit mask, the hexadecimal values must be combined using a bitwise or operation.
~]# opcontrol --event=event-name:sample-rate:unit-mask~]# opcontrol --event=event-name:sample-rate:unit-mask:0~]# opcontrol --event=event-name:sample-rate:unit-mask:1~]# opcontrol --event=event-name:sample-rate:unit-mask:kernel:0~]# opcontrol --event=event-name:sample-rate:unit-mask:kernel:1~]# opcontrol --separate=choicechoice can be one of the following:
none — do not separate the profiles (default)
library — generate per-application profiles for libraries
kernel — generate per-application profiles for the kernel and kernel modules
all — generate per-application profiles for libraries and per-application profiles for the kernel and kernel modules
--separate=library is used, the sample file name includes the name of the executable as well as the name of the library.
~]# opcontrol --startUsing log file /var/lib/oprofile/oprofiled.log Daemon started. Profiler running.
/root/.oprofile/daemonrc are used.
oprofiled, is started; it periodically writes the sample data to the /var/lib/oprofile/samples/ directory. The log file for the daemon is located at /var/lib/oprofile/oprofiled.log.
nmi_watchdog registers with the perf subsystem. Due to this, the perf subsystem grabs control of the performance counter registers at boot time, blocking OProfile from working.
nmi_watchdog=0 kernel parameter set, or run the following command to disable nmi_watchdog at run time:
~]# echo 0 > /proc/sys/kernel/nmi_watchdognmi_watchdog, use the following command:
~]# echo 1 > /proc/sys/kernel/nmi_watchdog~]# opcontrol --shutdownname with a unique descriptive name for the current session.
~]# opcontrol --save=name/var/lib/oprofile/samples/name/ is created and the current sample files are copied to it.
oprofiled, collects the samples and writes them to the /var/lib/oprofile/samples/ directory. Before reading the data, make sure all data has been written to this directory by executing the following command as root:
~]# opcontrol --dump/bin/bash becomes:
\{root\}/bin/bash/\{dep\}/\{root\}/bin/bash/CPU_CLK_UNHALTED.100000opreport
opannotate
oparchive can be used to address this problem.
opreportopreport tool provides an overview of all the executables being profiled.
Profiling through timer interrupt TIMER:0| samples| %| ------------------ 25926 97.5212 no-vmlinux 359 1.3504 pi 65 0.2445 Xorg 62 0.2332 libvte.so.4.4.0 56 0.2106 libc-2.3.4.so 34 0.1279 libglib-2.0.so.0.400.7 19 0.0715 libXft.so.2.1.2 17 0.0639 bash 8 0.0301 ld-2.3.4.so 8 0.0301 libgdk-x11-2.0.so.0.400.13 6 0.0226 libgobject-2.0.so.0.400.7 5 0.0188 oprofiled 4 0.0150 libpthread-2.3.4.so 4 0.0150 libgtk-x11-2.0.so.0.400.13 3 0.0113 libXrender.so.1.2.2 3 0.0113 du 1 0.0038 libcrypto.so.0.9.7a 1 0.0038 libpam.so.0.77 1 0.0038 libtermcap.so.2.0.8 1 0.0038 libX11.so.6.2 1 0.0038 libgthread-2.0.so.0.400.7 1 0.0038 libwnck-1.so.4.9.0
opreport man page for a list of available command line options, such as the -r option used to sort the output from the executable with the smallest number of samples to the one with the largest number of samples.
opreport:
~]# opreport mode executableexecutable must be the full path to the executable to be analyzed. mode must be one of the following:
-l opreport -l /lib/tls/libc-version.so:
samples % symbol name 12 21.4286 __gconv_transform_utf8_internal 5 8.9286 _int_malloc 4 7.1429 malloc 3 5.3571 __i686.get_pc_thunk.bx 3 5.3571 _dl_mcount_wrapper_check 3 5.3571 mbrtowc 3 5.3571 memcpy 2 3.5714 _int_realloc 2 3.5714 _nl_intern_locale_data 2 3.5714 free 2 3.5714 strcmp 1 1.7857 __ctype_get_mb_cur_max 1 1.7857 __unregister_atfork 1 1.7857 __write_nocancel 1 1.7857 _dl_addr 1 1.7857 _int_free 1 1.7857 _itoa_word 1 1.7857 calc_eclosure_iter 1 1.7857 fopen@@GLIBC_2.1 1 1.7857 getpid 1 1.7857 memmove 1 1.7857 msort_with_tmp 1 1.7857 strcpy 1 1.7857 strlen 1 1.7857 vfprintf 1 1.7857 write
-r in conjunction with the -l option.
-i symbol-name opreport -l -i __gconv_transform_utf8_internal /lib/tls/libc-version.so:
samples % symbol name 12 100.000 __gconv_transform_utf8_internal
-d -l. For example, the following output is from the command opreport -l -d __gconv_transform_utf8_internal /lib/tls/libc-version.so:
vma samples % symbol name 00a98640 12 100.000 __gconv_transform_utf8_internal 00a98640 1 8.3333 00a9868c 2 16.6667 00a9869a 1 8.3333 00a986c1 1 8.3333 00a98720 1 8.3333 00a98749 1 8.3333 00a98753 1 8.3333 00a98789 1 8.3333 00a98864 1 8.3333 00a98869 1 8.3333 00a98b08 1 8.3333
-l option except that for each symbol, each virtual memory address used is shown. For each virtual memory address, the number of samples and percentage of samples relative to the number of samples for the symbol is displayed.
-x symbol-name session:name /var/lib/oprofile/samples/ directory.
initrd file on boot up, the directory with the various kernel modules, or a locally created kernel module. As a result, when OProfile records sample for a module, it just lists the samples for the modules for an executable in the root directory, but this is unlikely to be the place with the actual code for the module. You will need to take some steps to make sure that analysis tools get the executable.
uname -a command, obtain the appropriate debuginfo package and install it on the machine.
~]# opcontrol --reset~]# opcontrol --setup --vmlinux=/usr/lib/debug/lib/modules/`uname -r`/vmlinux --event=CPU_CLK_UNHALTED:500000~]# opreport /ext4 -l --image-path /lib/modules/`uname -r`/kernel
CPU: Intel Westmere microarchitecture, speed 2.667e+06 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (No unit mask) count 500000
warning: could not check that the binary file /lib/modules/2.6.32-191.el6.x86_64/kernel/fs/ext4/ext4.ko has not been modified since the profile was taken. Results may be inaccurate.
samples % symbol name
1622 9.8381 ext4_iget
1591 9.6500 ext4_find_entry
1231 7.4665 __ext4_get_inode_loc
783 4.7492 ext4_ext_get_blocks
752 4.5612 ext4_check_dir_entry
644 3.9061 ext4_mark_iloc_dirty
583 3.5361 ext4_get_blocks
583 3.5361 ext4_xattr_get
479 2.9053 ext4_htree_store_dirent
469 2.8447 ext4_get_group_desc
414 2.5111 ext4_dx_find_entryopannotateopannotate tool tries to match the samples for particular instructions to the corresponding lines in the source code. The resulting files generated should have the samples for the lines at the left. It also puts in a comment at the beginning of each function listing the total samples for the function.
opannotate is as follows:
~]# opannotate --search-dirs src-dir --source executableopannotate man page for a list of additional command line options.
/dev/oprofile//dev/oprofile/ directory contains the file system for OProfile. Use the cat command to display the values of the virtual files in this file system. For example, the following command displays the type of processor OProfile detected:
~]# cat /dev/oprofile/cpu_type/dev/oprofile/ for each counter. For example, if there are 2 counters, the directories /dev/oprofile/0/ and dev/oprofile/1/ exist.
count — The interval between samples.
enabled — If 0, the counter is off and no samples are collected for it; if 1, the counter is on and samples are being collected for it.
event — The event to monitor.
extra — Used on machines with Nehalem processors to further specify the event to monitor.
kernel — If 0, samples are not collected for this counter event when the processor is in kernel-space; if 1, samples are collected even if the processor is in kernel-space.
unit_mask — Defines which unit masks are enabled for the counter.
user — If 0, samples are not collected for the counter event when the processor is in user-space; if 1, samples are collected even if the processor is in user-space.
cat command. For example:
~]# cat /dev/oprofile/0/countopreport can be used to determine how much processor time an application or service uses. If the system is used for multiple services but is under performing, the services consuming the most processor time can be moved to dedicated systems.
CPU_CLK_UNHALTED event can be monitored to determine the processor load over a given period of time. This data can then be used to determine if additional processors or a faster processor might improve system performance.
-agentlib:jvmti_oprofileoprof_start command as root at a shell prompt. To use the graphical interface, you will need to have the oprofile-gui package installed.
/root/.oprofile/daemonrc, and the application exits. Exiting the application does not stop OProfile from sampling.
oprof_start interface
vmlinux file for the kernel to monitor in the Kernel image file text field. To configure OProfile not to monitor the kernel, select No kernel image.
oprofiled daemon log includes more information.
opcontrol --separate=library command. If Per-application profiles, including kernel is selected, OProfile generates per-application profiles for the kernel and kernel modules as discussed in Section 22.2.3, “Separating Kernel and User-space Profiles”. This is equivalent to the opcontrol --separate=kernel command.
opcontrol --dump command.
netstat, ps, top, and iostat; however, SystemTap is designed to provide more filtering and analysis options for collected information.
/usr/share/doc/oprofile-version/oprofile.html — OProfile Manual
oprofile man page — Discusses opcontrol, opreport, opannotate, and ophelp
Table of Contents
rpm command instead of yum.
/usr/share/doc/kernel-doc-<kernel_version>/ directory.
VFAT file system. You can create bootable USB media on media formatted as ext2, ext3, or VFAT.
4 GB is required for a distribution DVD image, around 700 MB for a distribution CD image, or around 10 MB for a minimal boot media image.
boot.iso file from a Red Hat Enterprise Linux installation DVD, or installation CD-ROM#1, and you need a USB storage device formatted with the VFAT file system and around 16 MB of free space. The following procedure will not affect existing files on the USB storage device unless they have the same path names as the files that you copy onto it. To create USB boot media, perform the following commands as the root user:
~]# syslinux /dev/sdX1 sdX is the device name.
boot.iso and the USB storage device:
~]# mkdir /mnt/isoboot /mnt/diskbootboot.iso:
~]# mount -o loop boot.iso /mnt/isoboot~]# mount /dev/<sdX1> /mnt/diskbootboot.iso to the USB storage device:
~]# cp /mnt/isoboot/isolinux/* /mnt/diskbootisolinux.cfg file from boot.iso as the syslinux.cfg file for the USB device:
~]# grep -v local /mnt/isoboot/isolinux/isolinux.cfg > /mnt/diskboot/syslinux.cfgboot.iso and the USB storage device:
~]# umount /mnt/isoboot /mnt/diskbootmkbootdisk command as root. Refer to man mkbootdisk man page after installing the package for usage information.
yum list installed "kernel-*" at a shell prompt. The output will comprise some or all of the following packages, depending on the system's architecture, and the version numbers may differ:
~]# yum list installed "kernel-*"
kernel.x86_64 2.6.32-17.el6 installed
kernel-doc.noarch 2.6.32-17.el6 installed
kernel-firmware.noarch 2.6.32-17.el6 installed
kernel-headers.x86_64 2.6.32-17.el6 installed
-i argument with the rpm command to keep the old kernel. Do not use the -U option, since it overwrites the currently installed kernel, which creates boot loader problems. For example:
~]# rpm -ivh kernel-<kernel_version>.<arch>.rpm initramfs by running the dracut command. However, you usually don't need to create an initramfs manually: this step is automatically performed if the kernel and its associated packages are installed or upgraded from RPM packages distributed by Red Hat.
initramfs corresponding to your current kernel version exists and is specified correctly in the grub.conf configuration file by following this procedure:
/boot/ directory and find the kernel (vmlinuz-<kernel_version> ) and initramfs-<kernel_version> with the latest (most recent) version number:
~]# ls /boot/
config-2.6.32-17.el6.x86_64 lost+found
config-2.6.32-19.el6.x86_64 symvers-2.6.32-17.el6.x86_64.gz
config-2.6.32-22.el6.x86_64 symvers-2.6.32-19.el6.x86_64.gz
efi symvers-2.6.32-22.el6.x86_64.gz
grub System.map-2.6.32-17.el6.x86_64
initramfs-2.6.32-17.el6.x86_64.img System.map-2.6.32-19.el6.x86_64
initramfs-2.6.32-19.el6.x86_64.img System.map-2.6.32-22.el6.x86_64
initramfs-2.6.32-22.el6.x86_64.img vmlinuz-2.6.32-17.el6.x86_64
initrd-2.6.32-17.el6.x86_64kdump.img vmlinuz-2.6.32-19.el6.x86_64
initrd-2.6.32-19.el6.x86_64kdump.img vmlinuz-2.6.32-22.el6.x86_64
initrd-2.6.32-22.el6.x86_64kdump.img/boot/),
vmlinuz-2.6.32-22.el6.x86_64, and
initramfs file matching our kernel version, initramfs-2.6.32-22.el6.x86_64kdump.img, also exists.
/boot/ directory you may find several initrd-<version>kdump.img files. These are special files created by the Kdump mechanism for kernel debugging purposes, are not used to boot the system, and can safely be ignored.
initramfs-<kernel_version> file does not match the version of the latest kernel in /boot/, or, in certain other situations, you may need to generate an initramfs file with the Dracut utility. Simply invoking dracut as root without options causes it to generate an initramfs file in the /boot/ directory for the latest kernel present in that directory:
~]# dracut--force option if you want dracut to overwrite an existing initramfs (for example, if your initramfs has become corrupt). Otherwise dracut will refuse to overwrite the existing initramfs file:
~]# dracut
Will not override existing initramfs (/boot/initramfs-2.6.32-22.el6.x86_64.img) without --force dracut <initramfs_name> <kernel_version>:
~]# dracut "initramfs-$(uname -r).img" $(uname -r).ko) inside the parentheses of the add_dracutmodules="<module> [<more_modules>]" directive of the /etc/dracut.conf configuration file. You can list the file contents of an initramfs image file created by dracut by using the lsinitrd <initramfs_file> command:
~]# lsinitrd initramfs-2.6.32-22.el6.x86_64.img
initramfs-2.6.32-22.el6.x86_64.img:
========================================================================
dracut-004-17.el6
========================================================================
drwxr-xr-x 23 root root 0 May 3 22:34 .
drwxr-xr-x 2 root root 0 May 3 22:33 proc
-rwxr-xr-x 1 root root 7575 Mar 25 19:53 init
drwxr-xr-x 7 root root 0 May 3 22:34 etc
drwxr-xr-x 2 root root 0 May 3 22:34 etc/modprobe.d
[output truncated]man dracut and man dracut.conf for more information on options and usage.
grub.conf configuration file in the /boot/grub/ directory to ensure that an initrd initramfs-<kernel_version>.img exists for the kernel version you are booting. Refer to Section 23.6, “Verifying the Boot Loader” for more information.
addRamDisk command. This step is performed automatically if the kernel and its associated packages are installed or upgraded from the RPM packages distributed by Red Hat; thus, it does not need to be executed manually. To verify that it was created, use the command ls -l /boot/ to make sure the /boot/vmlinitrd-<kernel_version> file already exists (the <kernel_version> rpm, the kernel package creates an entry in the boot loader configuration file for that new kernel. However, rpm does not configure the new kernel to boot as the default kernel. You must do this manually when installing a new kernel with rpm.
rpm to ensure that the configuration is correct. Otherwise, the system may not be able to boot into Red Hat Enterprise Linux properly. If this happens, boot the system with the boot media created earlier and re-configure the boot loader.
| Architecture | Boot Loader | Refer to |
|---|---|---|
| x86 | GRUB | Section 23.6.1, “Configuring the GRUB Boot Loader” |
| AMD AMD64 or Intel 64 | GRUB | Section 23.6.1, “Configuring the GRUB Boot Loader” |
| IBM eServer System i | OS/400 | Section 23.6.2, “Configuring the OS/400 Boot Loader” |
| IBM eServer System p | YABOOT | Section 23.6.3, “Configuring the YABOOT Boot Loader” |
| IBM System z | z/IPL |
/boot/grub/grub.conf, contains a few lines with directives, such as default, timeout, splashimage and hiddenmenu (the last directive has no argument). The remainder of the file contains 4-line stanzas that each refer to an installed kernel. These stanzas always start with a title entry, after which the associated root, kernel and initrd directives should always be indented. Ensure that each stanza starts with a title that contains a version number (in parentheses) that matches the version number in the kernel /vmlinuz-<version_number> line of the same stanza.
# grub.conf generated by anaconda
[comments omitted]
default=1
timeout=0
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title Red Hat Enterprise Linux (2.6.32-22.el6.x86_64)
root (hd0,0)
kernel /vmlinuz-2.6.32-22.el6.x86_64 ro root=/dev/mapper/vg_vm6b-lv_root rd_LVM_LV=vg_vm6b/lv_root rd_NO_LUKS rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us rhgb quiet crashkernel=auto
initrd /initramfs-2.6.32-22.el6.x86_64.img
title Red Hat Enterprise Linux (2.6.32-19.el6.x86_64)
root (hd0,0)
kernel /vmlinuz-2.6.32-19.el6.x86_64 ro root=/dev/mapper/vg_vm6b-lv_root rd_LVM_LV=vg_vm6b/lv_root rd_NO_LUKS rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us rhgb quiet crashkernel=auto
initrd /initramfs-2.6.32-19.el6.x86_64.img
title Red Hat Enterprise Linux 6 (2.6.32-17.el6.x86_64)
root (hd0,0)
kernel /vmlinuz-2.6.32-17.el6.x86_64 ro root=/dev/mapper/vg_vm6b-lv_root rd_LVM_LV=vg_vm6b/lv_root rd_NO_LUKS rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us rhgb quiet
initrd /initramfs-2.6.32-17.el6.x86_64.img/boot/ partition was created, the paths to the kernel and the initramfs image are relative to /boot/. This is the case in Example 23.2, “/boot/grub/grub.conf”, above. Therefore the initrd /initramfs-2.6.32-22.el6.x86_64.img line in the first kernel stanza means that the initramfs image is actually located at /boot/initramfs-2.6.32-22.el6.x86_64.img when the root file system is mounted, and likewise for the kernel path (for example: kernel /vmlinuz-2.6.32-22.el6.x86_64) in each stanza of grub.conf.
grub.conf, the initrd directive must point to the location (relative to the /boot/ directory if it is on a separate partition) of the initramfs file corresponding to the same kernel version. This directive is called initrd because the previous tool which created initial RAM disk images, mkinitrd, created what were known as initrd files. Thus the grub.conf directive remains initrd to maintain compatibility with other tools. The file-naming convention of systems using the dracut utility to create the initial RAM disk image is: initramfs-<kernel_version>.img
mkinitrd. For information on using Dracut, refer to Section 23.5, “Verifying the Initial RAM Disk Image”.
kernel /vmlinuz-<kernel_version> line matches the version number of the initramfs image given on the initrd /initramfs-<kernel_version>.img line of each stanza. Refer to Procedure 23.1, “Verifying the Initial RAM Disk Image” for more information.
default= directive tells GRUB which kernel to boot by default. Each title in grub.conf represents a bootable kernel. GRUB counts the titled stanzas representing bootable kernels starting with 0. In Example 23.2, “/boot/grub/grub.conf”, the line default=1 indicates that GRUB will boot, by default, the second kernel entry, i.e. title Red Hat Enterprise Linux (2.6.32-19.el6.x86_64).
title entry in grub.conf, we would need to change the default value to 0.
rpm, verify that /boot/grub/grub.conf is correct, change the default= value to the new kernel (while remembering to count from 0), and reboot the computer into the new kernel. Ensure your hardware is detected by watching the boot process output.
timeout directive in grub.conf to 0, GRUB will not display its list of bootable kernels when the system starts up. In order to display this list when booting, press and hold any alphanumeric key while and immediately after BIOS information is displayed, and GRUB will present you with the GRUB menu.
/boot/vmlinitrd-<kernel-version> file is installed when you upgrade the kernel. However, you must use the dd command to configure the system to boot the new kernel.
cat /proc/iSeries/mf/side to determine the default side (either A, B, or C).
<kernel-version> is the version of the new kernel and <side> is the side from the previous command:
dd if=/boot/vmlinitrd-<kernel-version> of=/proc/iSeries/mf/<side>/vmlinux bs=8k/etc/aboot.conf as its configuration file. Confirm that the file contains an image section with the same version as the kernel package just installed, and likewise for the initramfs image:
boot=/dev/sda1 init-message=Welcome to Red Hat Enterprise Linux! Hit <TAB> for boot options partition=2 timeout=30 install=/usr/lib/yaboot/yaboot delay=10 nonvram image=/vmlinuz-2.6.32-17.EL label=old read-only initrd=/initramfs-2.6.32-17.EL.img append="root=LABEL=/" image=/vmlinuz-2.6.32-19.EL label=linux read-only initrd=/initramfs-2.6.32-19.EL.img append="root=LABEL=/"
default and set it to the label of the image stanza that contains the new kernel.
btrfs or NFS.
~]# yum install module-init-toolslsmod command:
~]$ lsmod
Module Size Used by
xfs 803635 1
exportfs 3424 1 xfs
vfat 8216 1
fat 43410 1 vfat
tun 13014 2
fuse 54749 2
ip6table_filter 2743 0
ip6_tables 16558 1 ip6table_filter
ebtable_nat 1895 0
ebtables 15186 1 ebtable_nat
ipt_MASQUERADE 2208 6
iptable_nat 5420 1
nf_nat 19059 2 ipt_MASQUERADE,iptable_nat
rfcomm 65122 4
ipv6 267017 33
sco 16204 2
bridge 45753 0
stp 1887 1 bridge
llc 4557 2 bridge,stp
bnep 15121 2
l2cap 45185 16 rfcomm,bnep
cpufreq_ondemand 8420 2
acpi_cpufreq 7493 1
freq_table 3851 2 cpufreq_ondemand,acpi_cpufreq
usb_storage 44536 1
sha256_generic 10023 2
aes_x86_64 7654 5
aes_generic 27012 1 aes_x86_64
cbc 2793 1
dm_crypt 10930 1
kvm_intel 40311 0
kvm 253162 1 kvm_intel
[output truncated]lsmod output specifies:
lsmod output is less verbose and considerably easier to read than the content of the /proc/modules pseudo-file.
modinfo <module_name> command.
.ko extension to the end of the name. Kernel module names do not have extensions: their corresponding files do.
e1000e module, which is the Intel PRO/1000 network driver, run:
~]#modinfo e1000efilename: /lib/modules/2.6.32-71.el6.x86_64/kernel/drivers/net/e1000e/e1000e.ko version: 1.2.7-k2 license: GPL description: Intel(R) PRO/1000 Network Driver author: Intel Corporation, <linux.nics@intel.com> srcversion: 93CB73D3995B501872B2982 alias: pci:v00008086d00001503sv*sd*bc*sc*i* alias: pci:v00008086d00001502sv*sd*bc*sc*i* [somealiaslines omitted] alias: pci:v00008086d0000105Esv*sd*bc*sc*i* depends: vermagic: 2.6.32-71.el6.x86_64 SMP mod_unload modversions parm: copybreak:Maximum size of packet that is copied to a new buffer on receive (uint) parm: TxIntDelay:Transmit Interrupt Delay (array of int) parm: TxAbsIntDelay:Transmit Absolute Interrupt Delay (array of int) parm: RxIntDelay:Receive Interrupt Delay (array of int) parm: RxAbsIntDelay:Receive Absolute Interrupt Delay (array of int) parm: InterruptThrottleRate:Interrupt Throttling Rate (array of int) parm: IntMode:Interrupt Mode (array of int) parm: SmartPowerDownEnable:Enable PHY smart power down (array of int) parm: KumeranLockLoss:Enable Kumeran lock loss workaround (array of int) parm: WriteProtectNVM:Write-protect NVM [WARNING: disabling this can lead to corrupted NVM] (array of int) parm: CrcStripping:Enable CRC Stripping, disable if your BMC needs the CRC (array of int) parm: EEE:Enable/disable on parts that support the feature (array of int)
modinfo output:
.ko kernel object file. You can use modinfo -n as a shortcut command for printing only the filename field.
modinfo -d as a shortcut command for printing only the description field.
alias field appears as many times as there are aliases for a module, or is omitted entirely if there are none.
depends field may be omitted from the output.
parm field presents one module parameter in the form parameter_name:descriptionparameter_name is the exact syntax you should use when using it as a module parameter on the command line, or in an option line in a .conf file in the /etc/modprobe.d/ directory; and,
description is a brief explanation of what the parameter does, along with an expectation for the type of value the parameter accepts (such as int, unit or array of int) in parentheses.
-p option. However, because useful value type information is omitted from modinfo -p output, it is more useful to run:
~]# modinfo e1000e | grep "^parm" | sort
parm: copybreak:Maximum size of packet that is copied to a new buffer on receive (uint)
parm: CrcStripping:Enable CRC Stripping, disable if your BMC needs the CRC (array of int)
parm: EEE:Enable/disable on parts that support the feature (array of int)
parm: InterruptThrottleRate:Interrupt Throttling Rate (array of int)
parm: IntMode:Interrupt Mode (array of int)
parm: KumeranLockLoss:Enable Kumeran lock loss workaround (array of int)
parm: RxAbsIntDelay:Receive Absolute Interrupt Delay (array of int)
parm: RxIntDelay:Receive Interrupt Delay (array of int)
parm: SmartPowerDownEnable:Enable PHY smart power down (array of int)
parm: TxAbsIntDelay:Transmit Absolute Interrupt Delay (array of int)
parm: TxIntDelay:Transmit Interrupt Delay (array of int)
parm: WriteProtectNVM:Write-protect NVM [WARNING: disabling this can lead to corrupted NVM] (array of int)modprobe <module_name> as root. For example, to load the wacom module, run:
~]# modprobe wacommodprobe attempts to load the module from /lib/modules/<kernel_version>/kernel/drivers/. In this directory, each type of module has its own subdirectory, such as net/ and scsi/, for network and SCSI interface drivers respectively.
modprobe command always takes dependencies into account when performing operations. When you ask modprobe to load a specific kernel module, it first examines the dependencies of that module, if there are any, and loads them if they are not already loaded into the kernel. modprobe resolves dependencies recursively: it will load all dependencies of dependencies, and so on, if necessary, thus ensuring that all dependencies are always met.
-v (or --verbose) option to cause modprobe to display detailed information about what it is doing, which may include loading module dependencies. The following is an example of loading the Fibre Channel over Ethernet module verbosely:
~]# modprobe -v fcoe
insmod /lib/modules/2.6.32-71.el6.x86_64/kernel/drivers/scsi/scsi_tgt.ko
insmod /lib/modules/2.6.32-71.el6.x86_64/kernel/drivers/scsi/scsi_transport_fc.ko
insmod /lib/modules/2.6.32-71.el6.x86_64/kernel/drivers/scsi/libfc/libfc.ko
insmod /lib/modules/2.6.32-71.el6.x86_64/kernel/drivers/scsi/fcoe/libfcoe.ko
insmod /lib/modules/2.6.32-71.el6.x86_64/kernel/drivers/scsi/fcoe/fcoe.komodprobe loaded the scsi_tgt, scsi_transport_fc, libfc and libfcoe modules as dependencies before finally loading fcoe. Also note that modprobe used the more “primitive” insmod command to insert the modules into the running kernel.
insmod command can also be used to load kernel modules, it does not resolve dependencies. Because of this, you should always load modules using modprobe instead.
modprobe -r <module_name> as root. For example, assuming that the wacom module is already loaded into the kernel, you can unload it by running:
~]# modprobe -r wacomwacom module,
wacom directly depends on, or,
wacom—through the dependency tree—depends on indirectly.
lsmod to obtain the names of the modules which are preventing you from unloading a certain module.
firewire_ohci module (because you believe there is a bug in it that is affecting system stability, for example), your terminal session might look similar to this:
~]#modinfo -F depends firewire_ohcidepends: firewire-core ~]#modinfo -F depends firewire_coredepends: crc-itu-t ~]#modinfo -F depends crc-itu-tdepends:
firewire_ohci depends on firewire_core, which itself depends on crc-itu-t.
firewire_ohci using the modprobe -v -r <module_name> command, where -r is short for --remove and -v for --verbose:
~]# modprobe -r -v firewire_ohci
rmmod /lib/modules/2.6.32-71.el6.x86_64/kernel/drivers/firewire/firewire-ohci.ko
rmmod /lib/modules/2.6.32-71.el6.x86_64/kernel/drivers/firewire/firewire-core.ko
rmmod /lib/modules/2.6.32-71.el6.x86_64/kernel/lib/crc-itu-t.kormmod command can be used to unload kernel modules, it is recommended to use modprobe -r instead.
modprobe -r, and then load it with modprobe along with a list of customized parameters. This method is often used when the module does not have many dependencies, or to test different combinations of parameters without making them persistent, and is the method covered in this section.
/etc/modprobe.d/ directory. This method makes the module parameters persistent by ensuring that they are set each time the module is loaded, such as after every reboot or modprobe command. This method is covered in Section 24.6, “Persistent Module Loading”, though the following information is a prerequisite.
modprobe to load a kernel module with custom parameters using the following command line format:
~]# modprobe <module_name> [parameter=value] modprobe will incorrectly interpret the values following spaces as additional parameters.
modprobe command silently succeeds with an exit status of 0 if:
modprobe command does not automatically reload the module, or alert you that it is already loaded.
e1000e module, which is the network driver for Intel PRO/1000 network adapters, as an example:
~]# lsmod |grep e1000e
~]# ~]# modprobe e1000e InterruptThrottleRate=3000,3000,3000 EEE=1<file_name>.modules/etc/sysconfig/modules/ directory, where <file_name> is any descriptive name of your choice. Your <file_name>.modulesfile_name.modules file#!/bin/sh
<file_name>.modulesmodules]# chmod +x <file_name>.modulesbluez-uinput.modules script loads the uinput module:
#!/bin/sh if [ ! -c /dev/input/uinput ] ; then exec /sbin/modprobe uinput >/dev/null 2>&1 fi
if-conditional statement on the third line ensures that the /dev/input/uinput file does not already exist (the ! symbol negates the condition), and, if that is the case, loads the uinput module by calling exec /sbin/modprobe uinput. Note that the uinput module creates the /dev/input/uinput file, so testing to see if that file exists serves as verification of whether the uinput module is loaded into the kernel.
>/dev/null 2>&1 clause at the end of that line redirects any output to /dev/null so that the modprobe command remains quiet.
alias and, possibly, options lines for each card in a user-created <module_name>.conf/etc/modprobe.d/ directory.
bonding kernel module and a special network interface, called a channel bonding interface. Channel bonding enables two or more network interfaces to act as one, simultaneously increasing the bandwidth and providing redundancy.
<bonding>.conf/etc/modprobe.d/ directory. Note that you can name this file anything you like as long as it ends with a .conf extension. Insert the following line in this new file:
alias bond<N> bonding<N> with the interface number, such as 0. For each configured channel bonding interface, there must be a corresponding entry in your new /etc/modprobe.d/<bonding>.conf file.
miimon or arp_interval and the arp_ip_target parameters. Refer to Section 24.7.2.1, “Bonding Module Directives” for a list of available options and how to quickly determine the best ones for your bonded interface.
BONDING_OPTS="<bonding parameters>" directive in your bonding interface configuration file (ifcfg-bond0 for example). Parameters to bonded interfaces can be configured without unloading (and reloading) the bonding module by manipulating files in the sysfs file system.
sysfs is a virtual file system that represents kernel objects as directories, files and symbolic links. sysfs can be used to query for information about kernel objects, and can also manipulate those objects through the use of normal file system commands. The sysfs virtual file system has a line in /etc/fstab, and is mounted under the /sys/ directory. All bonding interfaces can be configured dynamically by interacting with and manipulating files under the /sys/class/net/ directory.
ifcfg-bond0 by following the instructions in Section 8.2.2, “Channel Bonding Interfaces”. Insert the SLAVE=yes and MASTER=bond0 directives in the configuration files for each interface bonded to bond0. Once this is completed, you can proceed to testing the parameters.
ifconfig bond<N> up as root:
~]# ifconfig bond0 upifcfg-bond0 bonding interface file, you will be able to see bond0 listed in the output of running ifconfig (without any options):
~]# ifconfig
bond0 Link encap:Ethernet HWaddr 00:00:00:00:00:00
UP BROADCAST RUNNING MASTER MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
eth0 Link encap:Ethernet HWaddr 52:54:00:26:9E:F1
inet addr:192.168.122.251 Bcast:192.168.122.255 Mask:255.255.255.0
inet6 addr: fe80::5054:ff:fe26:9ef1/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:207 errors:0 dropped:0 overruns:0 frame:0
TX packets:205 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:70374 (68.7 KiB) TX bytes:25298 (24.7 KiB)
[output truncated]~]# cat /sys/class/net/bonding_masters
bond0/sys/class/net/bond<N>/bonding/ directory. First, the bond you are configuring must be taken down:
~]# ifconfig bond0 down~]# echo 1000 > /sys/class/net/bond0/bonding/miimonbalance-alb mode, you could run either:
~]# echo 6 > /sys/class/net/bond0/bonding/mode~]# echo balance-alb > /sys/class/net/bond0/bonding/modeifconfig bond<N> up. If you decide to change the options, take the interface down, modify its parameters using sysfs, bring it back up, and re-test.
BONDING_OPTS= directive of the /etc/sysconfig/network-scripts/ifcfg-bond<N> file for the bonding interface you are configuring. Whenever that bond is brought up (for example, by the system during the boot sequence if the ONBOOT=yes directive is set), the bonding options specified in the BONDING_OPTS will take effect for that bond. For more information on configuring bonding interfaces (and BONDING_OPTS), refer to Section 8.2.2, “Channel Bonding Interfaces”.
parm in modinfo bonding output, or the exhaustive descriptions in the bonding.txt file in the kernel-doc package (see Section 24.8, “Additional Resources”).
arp_interval=<time_in_milliseconds> arp_interval and arp_ip_target parameters are specified, or, alternatively, the miimon parameter is specified. Failure to do so can cause degradation of network performance in the event that a link fails.
mode=0 or mode=1 (the two load-balancing modes), the network switch must be configured to distribute packets evenly across the NICs. For more information on how to accomplish this, refer to /usr/share/doc/kernel-doc-<kernel_version>/Documentation/networking/bonding.txt
0 by default, which disables it.
arp_ip_target=<ip_address>[,<ip_address_2>,…<ip_address_16>] arp_interval parameter is enabled. Up to 16 IP addresses can be specified in a comma separated list.
arp_validate=<value> none. Other valid values are active, backup, and all.
debug=<number> 0 — Debug messages are disabled. This is the default.
1 — Debug messages are enabled.
downdelay=<time_in_milliseconds> miimon parameter. The value is set to 0 by default, which disables it.
<value> slow or 0 — Default setting. This specifies that partners should transmit LACPDUs every 30 seconds.
fast or 1 — Specifies that partners should transmit LACPDUs every 1 second.
miimon=<time_in_milliseconds> ~]# ethtool <interface_name> | grep "Link detected:"<interface_name> with the name of the device interface, such as eth0, not the bond interface. If MII is supported, the command returns:
Link detected: yes
0 (the default), turns this feature off. When configuring this setting, a good starting point for this parameter is 100.
arp_interval and arp_ip_target parameters are specified, or, alternatively, the miimon parameter is specified. Failure to do so can cause degradation of network performance in the event that a link fails.
mode=<value> <value> can be one of:
balance-rr or 0 — Sets a round-robin policy for fault tolerance and load balancing. Transmissions are received and sent out sequentially on each bonded slave interface beginning with the first one available.
active-backup or 1 — Sets an active-backup policy for fault tolerance. Transmissions are received and sent out via the first available bonded slave interface. Another bonded slave interface is only used if the active bonded slave interface fails.
balance-xor or 2 — Sets an XOR (exclusive-or) policy for fault tolerance and load balancing. Using this method, the interface matches up the incoming request's MAC address with the MAC address for one of the slave NICs. Once this link is established, transmissions are sent out sequentially beginning with the first available interface.
broadcast or 3 — Sets a broadcast policy for fault tolerance. All transmissions are sent on all slave interfaces.
802.3ad or 4 — Sets an IEEE 802.3ad dynamic link aggregation policy. Creates aggregation groups that share the same speed and duplex settings. Transmits and receives on all slaves in the active aggregator. Requires a switch that is 802.3ad compliant.
balance-tlb or 5 — Sets a Transmit Load Balancing (TLB) policy for fault tolerance and load balancing. The outgoing traffic is distributed according to the current load on each slave interface. Incoming traffic is received by the current slave. If the receiving slave fails, another slave takes over the MAC address of the failed slave.
balance-alb or 6 — Sets an Active Load Balancing (ALB) policy for fault tolerance and load balancing. Includes transmit and receive load balancing for IPV4 traffic. Receive load balancing is achieved through ARP negotiation.
num_unsol_na=<number> 0 - 255; the default value is 1. This parameter affects only the active-backup mode.
primary=<interface_name> eth0, of the primary device. The primary device is the first of the bonding interfaces to be used and is not abandoned unless it fails. This setting is particularly useful when one NIC in the bonding interface is faster and, therefore, able to handle a bigger load.
active-backup mode. Refer to /usr/share/doc/kernel-doc-<kernel-version>/Documentation/networking/bonding.txt for more information.
primary_reselect=<value> always or 0 (default) — The primary slave becomes the active slave whenever it comes back up.
better or 1 — The primary slave becomes the active slave when it comes back up, if the speed and duplex of the primary slave is better than the speed and duplex of the current active slave.
failure or 2 — The primary slave becomes the active slave only if the current active slave fails and the primary slave is up.
primary_reselect setting is ignored in two cases:
primary_reselect policy via sysfs will cause an immediate selection of the best active slave according to the new policy. This may or may not result in a change of the active slave, depending upon the circumstances
updelay=<time_in_milliseconds> miimon parameter. The value is set to 0 by default, which disables it.
use_carrier=<number> miimon should use MII/ETHTOOL ioctls or netif_carrier_ok() to determine the link state. The netif_carrier_ok() function relies on the device driver to maintains its state with netif_carrier_on/off; most device drivers support this function.
netif_carrier_on/off.
1 — Default setting. Enables the use of netif_carrier_ok().
0 — Enables the use of MII/ETHTOOL ioctls.
netif_carrier_on/off.
xmit_hash_policy=<value> balance-xor and 802.3ad modes. Possible values are:
0 or layer2 — Default setting. This parameter uses the XOR of hardware MAC addresses to generate the hash. The formula used is:
(<source_MAC_address>XOR<destination_MAC>) MODULO<slave_count>
1 or layer3+4 — Uses upper layer protocol information (when available) to generate the hash. This allows for traffic to a particular network peer to span multiple slaves, although a single connection will not span multiple slaves.
((<source_port>XOR<dest_port>) XOR ((<source_IP>XOR<dest_IP>) AND0xffff) MODULO<slave_count>
layer2 transmit hash policy.
2 or layer2+3 — Uses a combination of layer2 and layer3 protocol information to generate the hash.
(((<source_IP>XOR<dest_IP>) AND0xffff) XOR (<source_MAC>XOR<destination_MAC>)) MODULO<slave_count>
man lsmod — The manual page for the lsmod command.
man modinfo — The manual page for the modinfo command.
man modprobe — The manual page for the modprobe command.
man rmmod — The manual page for the rmmod command.
man ethtool — The manual page for the ethtool command.
man mii-tool — The manual page for the mii-tool command.
/usr/share/doc/kernel-doc-<kernel_version>/Documentation/ — This directory, which is provided by the kernel-doc package, contains information on the kernel, kernel modules, and their respective parameters. Before accessing the kernel documentation, you must run the following command as root:
~]# yum install kernel-doce1000e driver.
kdump is an advanced crash dumping mechanism. When enabled, the system is booted from the context of another kernel. This second kernel reserves a small amount of memory, and its only purpose is to capture the core dump image in case the system crashes. Since being able to analyze the core dump helps significantly to determine the exact cause of the system failure, it is strongly recommended to have this feature enabled.
kdump service in Red Hat Enterprise Linux, and provides a brief overview of how to analyze the resulting core dump using the crash debugging utility.
kdump service: at the first boot, using the Kernel Dump Configuration graphical utility, and doing so manually on the command line. It also describes how to test the configuration to verify that everything works as expected.
Intel IOMMU driver can occasionally prevent the kdump service from capturing the core dump image. To use kdump on Intel architectures reliably, it is advised that the IOMMU support is disabled.
kdump service, you must have the kexec-tools package installed. To do so, type the following at a shell prompt as root:
yum install kexec-toolskdump, navigate to the Kdump section, and follow the instructions below.
kdump crash recovery is enabled, the minimum memory requirements increase by the amount of memory reserved for it. This value is determined by a user, and defaults to 128 MB.
kdump daemon at boot time, select the Enable kdump? check box. This will enable the service for runlevels 2, 3, 4, and 5, and start it for the current session. Similarly, unselecting the check box will disable it for all runlevels and stop the service immediately.
kdump kernel, click the up and down arrow buttons next to the Kdump Memory field to increase or decrease the value. Notice that the Usable System Memory field changes accordingly showing you the remaining memory that will be available to the system.
system-config-kdump at a shell prompt (for example, xterm or GNOME Terminal). You will be presented with a window as shown in Figure 25.1, “Basic Settings”.
kdump as well as to enable or disable starting the service at boot time. When you are done, click to save the changes. The system reboot will be requested, and unless you are already authenticated, you will be prompted to enter the superuser password.
kdump crash recovery is enabled, the minimum memory requirements increase by the amount of memory reserved for it. This value is determined by a user, and defaults to 128 MB.
kdump daemon at boot time, click the button on the toolbar. This will enable the service for runlevels 2, 3, 4, and 5, and start it for the current session. Similarly, clicking the button will disable it for all runlevels and stop the service immediately.
kdump kernel. To do so, select the Manual kdump memory settings radio button, and click the up and down arrow buttons next to the New kdump Memory field to increase or decrease the value. Notice that the Usable Memory field changes accordingly showing you the remaining memory that will be available to the system.
vmcore dump. It can be either stored as a file in a local file system, written directly to a device, or sent over a network using the NFS (Network File System) or SSH (Secure Shell) protocol.
| Type | Supported Targets | Unsupported Targets |
|---|---|---|
| Raw device | All locally attached raw disks and partitions. | — |
| Local file system |
ext2, ext3, ext4, minix file systems on directly attached disk drives, hardware RAID logical drives, LVM devices, and mdraid arrays.
|
The eCryptfs file system.
|
| Remote directory |
Remote directories accessed using the NFS or SSH protocol over IPv4.
|
Remote directories on the rootfs file system accessed using the NFS protocol.
|
Remote directories accessed using the iSCSI protocol over hardware initiators.
|
Remote directories accessed using the iSCSI protocol over software initiators.
| |
| — |
Remote directories accessed over IPv6.
| |
Remote directories accessed using the SMB/CIFS protocol.
| ||
Remote directories accessed using the FCoE (Fibre Channel over Ethernet) protocol.
| ||
| Remote directories accessed using wireless network interfaces. | ||
| Multipath-based storages. |
hpsa driver, kdump is unable to save the dump to a storage that uses this driver for HP Smart Array Controllers. If this applies to your machine, it is advised that you save the dump to a remote system using the NFS or SSH protocol instead.
vmcore dump.
makedumpfile core collector, edit the Core collector text field; see Section 25.1.3.3, “Configuring the Core Collector” for more information.
root. To do so, run the following command:
su -kdump kernel, open the /boot/grub/grub.conf file in a text editor such as vi or nano, and add the crashkernel=<size>M parameter to the list of kernel options as shown in Example 25.1, “A sample /boot/grub/grub.conf file”.
# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE: You have a /boot partition. This means that
# all kernel and initrd paths are relative to /boot/, eg.
# root (hd0,0)
# kernel /vmlinuz-version ro root=/dev/sda3
# initrd /initrd
#boot=/dev/sda
default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title Red Hat Enterprise Linux (2.6.32-54.el6.i686)
root (hd0,0)
kernel /boot/vmlinuz-2.6.32-54.el6.i686 root=/dev/sda3 ro crashkernel=128M
initrd /initramfs-2.6.32-54.el6.i686.img
kdump crash recovery is enabled, the minimum memory requirements increase by the amount of memory reserved for it. This value is determined by a user, and defaults to 128 MB, as lower values proved to be unreliable. For more information on minimum memory requirements for Red Hat Enterprise Linux 6, refer to the Required minimums section of the Red Hat Enterprise Linux comparison chart.
vmcore file in the /var/crash/ directory of the local file system. To change this, open the /etc/kdump.conf configuration file in a text editor such as vi or nano, and edit the options as described below.
#path /var/crash line, and replace the value with a desired directory path. Optionally, if you wish to write the file to a different partition, follow the same procedure with the #ext4 /dev/sda3 line as well, and change both the file system type and the device (a device name, a file system label, and UUID are all supported) accordingly. For example:
ext3 /dev/sda4 path /usr/local/cores
#raw /dev/sda5 line, and replace the value with a desired device name. For example:
raw /dev/sdb1
#net my.server.com:/export/tmp line, and replace the value with a valid hostname and directory path. For example:
net penguin.example.com:/export/cores
#net user@my.server.com line, and replace the value with a valid username and hostname. For example:
net john@penguin.example.com
hpsa driver, kdump is unable to save the dump to a storage that uses this driver for HP Smart Array Controllers. If this applies to your machine, it is advised that you save the dump to a remote system using the NFS or SSH protocol instead.
vmcore dump file, kdump allows you to specify an external application (that is, a core collector) to compress the data, and optionally leave out all irrelevant information. Currently, the only fully supported core collector is makedumpfile.
/etc/kdump.conf configuration file in a text editor such as vi or nano, remove the hash sign (“#”) from the beginning of the #core_collector makedumpfile -c --message-level 1 -d 31 line, and edit the command line options as described below.
-c parameter. For example:
core_collector makedumpfile -c
-d value parameter, where value is a sum of values of pages you want to omit as described in Table 25.2, “Supported filtering levels”. For example, to remove both zero and free pages, use the following:
core_collector makedumpfile -d 17 -c
makedumpfile for a complete list of available options.
| Option | Description |
|---|---|
1
| Zero pages |
2
| Cache pages |
4
| Cache private |
8
| User pages |
16
| Free pages |
/sbin/init is run. To change this behavior, open the /etc/kdump.conf configuration file in a text editor such as vi or nano, remove the hash sign (“#”) from the beginning of the #default shell line, and replace the value with a desired action as described in Table 25.3, “Supported actions”. For example:
default halt
| Option | Description |
|---|---|
reboot
| Reboot the system, losing the core in the process. |
halt
| After attempting to capture a core, halt the system no matter if it succeeded. |
poweroff
| Power off the system. |
shell
| Run the msh session from within the initramfs, allowing a user to record the core manually. |
kdump daemon at boot time, type the following at a shell prompt:
chkconfig kdump on2, 3, 4, and 5. Similarly, typing chkconfig kdump off will disable it for all runlevels. To start the service in the current session, use the following command:
service kdump startkdump enabled, and make sure that the service is running (refer to Section 9.3, “Running the Services” for more information on how to run a service in Red Hat Enterprise Linux). For example:
~]# service kdump status
Kdump is operationalecho 1 > /proc/sys/kernel/sysrqecho c > /proc/sysrq-trigger
address-YYYY-MM-DD-HH:MM:SS/vmcore/var/crash/ by default).
~]# tree --charset=ascii /var/crash
/var/crash
`-- 127.0.0.1-2010-08-25-08:45:02
`-- vmcore
1 directory, 1 filenetdump, diskdump, xendump, or kdump.
vmcore dump file, you must have the crash and kernel-debuginfo packages installed. To install these packages, type the following at a shell prompt as root:
yum install crashdebuginfo-install kernel
crash /var/crash/timestamp/vmcore /usr/lib/debug/lib/modules/kernel/vmlinuxkernel version should be the same that was captured by kdump. To find out which kernel you are currently running, use the uname -r command.
~]#crash /usr/lib/debug/lib/modules/2.6.32-69.el6.i686/vmlinux \/var/crash/127.0.0.1-2010-08-25-08:45:02/vmcorecrash 5.0.0-23.el6 Copyright (C) 2002-2010 Red Hat, Inc. Copyright (C) 2004, 2005, 2006 IBM Corporation Copyright (C) 1999-2006 Hewlett-Packard Co Copyright (C) 2005, 2006 Fujitsu Limited Copyright (C) 2006, 2007 VA Linux Systems Japan K.K. Copyright (C) 2005 NEC Corporation Copyright (C) 1999, 2002, 2007 Silicon Graphics, Inc. Copyright (C) 1999, 2000, 2001, 2002 Mission Critical Linux, Inc. This program is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Enter "help copying" to see the conditions. This program has absolutely no warranty. Enter "help warranty" for details. GNU gdb (GDB) 7.0 Copyright (C) 2009 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "i686-pc-linux-gnu"... KERNEL: /usr/lib/debug/lib/modules/2.6.32-69.el6.i686/vmlinux DUMPFILE: /var/crash/127.0.0.1-2010-08-25-08:45:02/vmcore [PARTIAL DUMP] CPUS: 4 DATE: Wed Aug 25 08:44:47 2010 UPTIME: 00:09:02 LOAD AVERAGE: 0.00, 0.01, 0.00 TASKS: 140 NODENAME: hp-dl320g5-02.lab.bos.redhat.com RELEASE: 2.6.32-69.el6.i686 VERSION: #1 SMP Tue Aug 24 10:31:45 EDT 2010 MACHINE: i686 (2394 Mhz) MEMORY: 8 GB PANIC: "Oops: 0002 [#1] SMP " (check log for details) PID: 5591 COMMAND: "bash" TASK: f196d560 [THREAD_INFO: ef4da000] CPU: 2 STATE: TASK_RUNNING (PANIC) crash>
log command at the interactive prompt.
crash> log
... several lines omitted ...
EIP: 0060:[<c068124f>] EFLAGS: 00010096 CPU: 2
EIP is at sysrq_handle_crash+0xf/0x20
EAX: 00000063 EBX: 00000063 ECX: c09e1c8c EDX: 00000000
ESI: c0a09ca0 EDI: 00000286 EBP: 00000000 ESP: ef4dbf24
DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
Process bash (pid: 5591, ti=ef4da000 task=f196d560 task.ti=ef4da000)
Stack:
c068146b c0960891 c0968653 00000003 00000000 00000002 efade5c0 c06814d0
<0> fffffffb c068150f b7776000 f2600c40 c0569ec4 ef4dbf9c 00000002 b7776000
<0> efade5c0 00000002 b7776000 c0569e60 c051de50 ef4dbf9c f196d560 ef4dbfb4
Call Trace:
[<c068146b>] ? __handle_sysrq+0xfb/0x160
[<c06814d0>] ? write_sysrq_trigger+0x0/0x50
[<c068150f>] ? write_sysrq_trigger+0x3f/0x50
[<c0569ec4>] ? proc_reg_write+0x64/0xa0
[<c0569e60>] ? proc_reg_write+0x0/0xa0
[<c051de50>] ? vfs_write+0xa0/0x190
[<c051e8d1>] ? sys_write+0x41/0x70
[<c0409adc>] ? syscall_call+0x7/0xb
Code: a0 c0 01 0f b6 41 03 19 d2 f7 d2 83 e2 03 83 e0 cf c1 e2 04 09 d0 88 41 03 f3 c3 90 c7 05 c8 1b 9e c0 01 00 00 00 0f ae f8 89 f6 <c6> 05 00 00 00 00 01 c3 89 f6 8d bc 27 00 00 00 00 8d 50 d0 83
EIP: [<c068124f>] sysrq_handle_crash+0xf/0x20 SS:ESP 0068:ef4dbf24
CR2: 0000000000000000help log for more information on the command usage.
bt command at the interactive prompt. You can use bt pid to display the backtrace of the selected process.
crash> bt
PID: 5591 TASK: f196d560 CPU: 2 COMMAND: "bash"
#0 [ef4dbdcc] crash_kexec at c0494922
#1 [ef4dbe20] oops_end at c080e402
#2 [ef4dbe34] no_context at c043089d
#3 [ef4dbe58] bad_area at c0430b26
#4 [ef4dbe6c] do_page_fault at c080fb9b
#5 [ef4dbee4] error_code (via page_fault) at c080d809
EAX: 00000063 EBX: 00000063 ECX: c09e1c8c EDX: 00000000 EBP: 00000000
DS: 007b ESI: c0a09ca0 ES: 007b EDI: 00000286 GS: 00e0
CS: 0060 EIP: c068124f ERR: ffffffff EFLAGS: 00010096
#6 [ef4dbf18] sysrq_handle_crash at c068124f
#7 [ef4dbf24] __handle_sysrq at c0681469
#8 [ef4dbf48] write_sysrq_trigger at c068150a
#9 [ef4dbf54] proc_reg_write at c0569ec2
#10 [ef4dbf74] vfs_write at c051de4e
#11 [ef4dbf94] sys_write at c051e8cc
#12 [ef4dbfb0] system_call at c0409ad5
EAX: ffffffda EBX: 00000001 ECX: b7776000 EDX: 00000002
DS: 007b ESI: 00000002 ES: 007b EDI: b7776000
SS: 007b ESP: bfcb2088 EBP: bfcb20b4 GS: 0033
CS: 0073 EIP: 00edc416 ERR: 00000004 EFLAGS: 00000246help bt for more information on the command usage.
ps command at the interactive prompt. You can use ps pid to display the status of the selected process.
crash> ps
PID PPID CPU TASK ST %MEM VSZ RSS COMM
> 0 0 0 c09dc560 RU 0.0 0 0 [swapper]
> 0 0 1 f7072030 RU 0.0 0 0 [swapper]
0 0 2 f70a3a90 RU 0.0 0 0 [swapper]
> 0 0 3 f70ac560 RU 0.0 0 0 [swapper]
1 0 1 f705ba90 IN 0.0 2828 1424 init
... several lines omitted ...
5566 1 1 f2592560 IN 0.0 12876 784 auditd
5567 1 2 ef427560 IN 0.0 12876 784 auditd
5587 5132 0 f196d030 IN 0.0 11064 3184 sshd
> 5591 5587 2 f196d560 RU 0.0 5084 1648 bashhelp ps for more information on the command usage.
vm command at the interactive prompt. You can use vm pid to display information on the selected process.
crash> vm
PID: 5591 TASK: f196d560 CPU: 2 COMMAND: "bash"
MM PGD RSS TOTAL_VM
f19b5900 ef9c6000 1648k 5084k
VMA START END FLAGS FILE
f1bb0310 242000 260000 8000875 /lib/ld-2.12.so
f26af0b8 260000 261000 8100871 /lib/ld-2.12.so
efbc275c 261000 262000 8100873 /lib/ld-2.12.so
efbc2a18 268000 3ed000 8000075 /lib/libc-2.12.so
efbc23d8 3ed000 3ee000 8000070 /lib/libc-2.12.so
efbc2888 3ee000 3f0000 8100071 /lib/libc-2.12.so
efbc2cd4 3f0000 3f1000 8100073 /lib/libc-2.12.so
efbc243c 3f1000 3f4000 100073
efbc28ec 3f6000 3f9000 8000075 /lib/libdl-2.12.so
efbc2568 3f9000 3fa000 8100071 /lib/libdl-2.12.so
efbc2f2c 3fa000 3fb000 8100073 /lib/libdl-2.12.so
f26af888 7e6000 7fc000 8000075 /lib/libtinfo.so.5.7
f26aff2c 7fc000 7ff000 8100073 /lib/libtinfo.so.5.7
efbc211c d83000 d8f000 8000075 /lib/libnss_files-2.12.so
efbc2504 d8f000 d90000 8100071 /lib/libnss_files-2.12.so
efbc2950 d90000 d91000 8100073 /lib/libnss_files-2.12.so
f26afe00 edc000 edd000 4040075
f1bb0a18 8047000 8118000 8001875 /bin/bash
f1bb01e4 8118000 811d000 8101873 /bin/bash
f1bb0c70 811d000 8122000 100073
f26afae0 9fd9000 9ffa000 100073
... several lines omitted ...help vm for more information on the command usage.
files command at the interactive prompt. You can use files pid to display files opened by the selected process.
crash> files
PID: 5591 TASK: f196d560 CPU: 2 COMMAND: "bash"
ROOT: / CWD: /root
FD FILE DENTRY INODE TYPE PATH
0 f734f640 eedc2c6c eecd6048 CHR /pts/0
1 efade5c0 eee14090 f00431d4 REG /proc/sysrq-trigger
2 f734f640 eedc2c6c eecd6048 CHR /pts/0
10 f734f640 eedc2c6c eecd6048 CHR /pts/0
255 f734f640 eedc2c6c eecd6048 CHR /pts/0help files for more information on the command usage.
exit or q.
crash> exit
~]#man kdump.conf/etc/kdump.conf configuration file containing the full documentation of available options.
man makedumpfilemakedumpfile core collector containing the full documentation on its usage.
man kexeckexec containing the full documentation on its usage.
man crash/usr/share/doc/kexec-tools-version/kexec-kdump-howto.txtkdump and kexec installation and usage.
kexec and kdump configuration.
kdump targets.
eth[0123…], but these names do not necessarily correspond to actual labels on the chassis. Modern server platforms with multiple network adapters can encounter non-deterministic and counter-intuitive naming of these interfaces. This affects both network adapters embedded on the motherboard (Lan-on-Motherboard, or LOM) and add-in (single and multiport) adapters.
eth[0123…] to the new naming convention as shown in Table A.1, “The new naming convention”.
| Device | Old Name | New Name |
|---|---|---|
| Embedded network interface (LOM) |
eth[0123…]
|
em[1234…][a]
|
| PCI card network interface |
eth[0123…]
|
p<[b]
|
| Virtual function |
eth[0123…]
|
p<[c]
|
[a]
New enumeration starts at 1.
[b]
For example: p3p4
[c]
For example: p3p4_1
| ||
/etc/udev/rules.d/70-persistent-net.rules to change the device names to anything desired; those will take precedence over this physical location naming convention.
Dell PowerEdge, C Series, and Precision Workstation systems. For more details regarding the impact on Dell systems, visit https://access.redhat.com/kb/docs/DOC-47318.
eth[0123…] naming convention will continue to be used.
base package group in Red Hat Enterprise Linux 6. All install options, except for , include this package. It is not installed on upgrades of Red Hat Enterprise Linux 6.0 to RHEL 6.1.
biosdevname=0biosdevname=1biosdevname install option is specified, it must remain as a boot option for the lifetime of the system.
ksdevice parameter; these kickstart files will need to be updated to use the network device's MAC address or the network device's new name.
/etc/udev/rules.d/70-persistent-net.rules file and the HWADDR lines from all /etc/sysconfig/network-scripts/ifcfg-* files. In addition, rename those ifcfg-* files to use this new naming convention. The new names will be in effect after reboot. Remember to update any custom scripts, iptables rules, and service configuration files that might include network interface names.
x86_64.rpm.
.tar.gz files.
rpm --help or man rpm. You can also refer to Section B.5, “Additional Resources” for more information on RPM.
tree-1.5.3-2.el6.x86_64.rpm. The file name includes the package name (tree), version (1.5.3), release (2), operating system major version (el6) and CPU architecture (x86_64).
rpm's -U option to:
rpm -U <rpm_file> is able to perform the function of either upgrading or installing as is appropriate for the package.
tree-1.5.3-2.el6.x86_64.rpm package is in the current directory, log in as root and type the following command at a shell prompt to either upgrade or install the tree package as determined by rpm:
rpm -Uvh tree-1.5.3-2.el6.x86_64.rpm-v and -h options (which are combined with -U) cause rpm to print more verbose output and display a progress meter using hash signs.
Preparing... ########################################### [100%] 1:tree ########################################### [100%]
rpm provides two different options for installing packages: the aforementioned -U option (which historically stands for upgrade), and the -i option, historically standing for install. Because the -U option subsumes both install and upgrade functions, we recommend to use rpm -Uvh with all packages except kernel packages.
-i option to simply install a new kernel package instead of upgrading it. This is because using the -U option to upgrade a kernel package removes the previous (older) kernel package, which could render the system unable to boot if there is a problem with the new kernel. Therefore, use the rpm -i <kernel_package> command to install a new kernel without replacing any older kernel packages. For more information on installing kernel packages, refer to Chapter 23, Manually Upgrading the Kernel.
error: tree-1.5.3-2.el6.x86_64.rpm: Header V3 RSA/SHA256 signature: BAD, key ID d22e77f2
error: tree-1.5.3-2.el6.x86_64.rpm: Header V3 RSA/SHA256 signature: BAD, key ID d22e77f2
NOKEY:
warning: tree-1.5.3-2.el6.x86_64.rpm: Header V3 RSA/SHA1 signature: NOKEY, key ID 57bbccba
Preparing... ########################################### [100%] package tree-1.5.3-2.el6.x86_64 is already installed
--replacepkgs option, which tells RPM to ignore the error:
rpm -Uvh --replacepkgs tree-1.5.3-2.el6.x86_64.rpmPreparing... ################################################## file /usr/bin/foobar from install of foo-1.0-1.el6.x86_64 conflicts with file from package bar-3.1.1.el6.x86_64
--replacefiles option:
rpm -Uvh --replacefiles foo-1.0-1.el6.x86_64.rpmerror: Failed dependencies: bar.so.3()(64bit) is needed by foo-1.0-1.el6.x86_64
rpm -Uvh foo-1.0-1.el6.x86_64.rpm bar-3.1.1.el6.x86_64.rpmPreparing... ########################################### [100%] 1:foo ########################################### [ 50%] 2:bar ########################################### [100%]
--whatprovides option to determine which package contains the required file.
rpm -q --whatprovides "bar.so.3"bar.so.3 is in the RPM database, the name of the package is displayed:
bar-3.1.1.el6.i586.rpm
rpm to install a package that gives us a Failed dependencies error (using the --nodeps option), this is not recommended, and will usually result in the installed package failing to run. Installing or removing packages with rpm --nodeps can cause applications to misbehave and/or crash, and can cause serious package management problems or, possibly, system failure. For these reasons, it is best to heed such warnings; the package manager—whether RPM, Yum or PackageKit—shows us these warnings and suggests possible fixes because accounting for dependencies is critical. The Yum package manager can perform dependency resolution and fetch dependencies from online repositories, making it safer, easier and smarter than forcing rpm to carry out actions without regard to resolving dependencies.
saving /etc/foo.conf as /etc/foo.conf.rpmsave
foo.conf.rpmnew, and leave the configuration file you modified untouched. You should still resolve any conflicts between your modified configuration file and the new one, usually by merging changes from the old one to the new one with a diff program.
package foo-2.0-1.el6.x86_64.rpm (which is newer than foo-1.0-1) is already installed
--oldpackage option:
rpm -Uvh --oldpackage foo-1.0-1.el6.x86_64.rpmrpm -e foo
foo, not the name of the original package file, foo-1.0-1.el6.x86_64. If you attempt to uninstall a package using the rpm -e command and the original full file name, you will receive a package name error.
rpm -e ghostscript
error: Failed dependencies:
libgs.so.8()(64bit) is needed by (installed) libspectre-0.2.2-3.el6.x86_64
libgs.so.8()(64bit) is needed by (installed) foomatic-4.0.3-1.el6.x86_64
libijs-0.35.so()(64bit) is needed by (installed) gutenprint-5.2.4-5.el6.x86_64
ghostscript is needed by (installed) printer-filters-1.1-4.el6.noarch<library_name>.so.<number> ~]# rpm -q --whatprovides "libgs.so.8()(64bit)"
ghostscript-8.70-1.el6.x86_64rpm to remove a package that gives us a Failed dependencies error (using the --nodeps option), this is not recommended, and may cause harm to other installed applications. Installing or removing packages with rpm --nodeps can cause applications to misbehave and/or crash, and can cause serious package management problems or, possibly, system failure. For these reasons, it is best to heed such warnings; the package manager—whether RPM, Yum or PackageKit—shows us these warnings and suggests possible fixes because accounting for dependencies is critical. The Yum package manager can perform dependency resolution and fetch dependencies from online repositories, making it safer, easier and smarter than forcing rpm to carry out actions without regard to resolving dependencies.
rpm -Fvh foo-2.0-1.el6.x86_64.rpm*.rpm glob:
rpm -Fvh *.rpm/var/lib/rpm/, and is used to query what packages are installed, what versions each package is, and to calculate any changes to any files in the package since installation, among other use cases.
-q option. The rpm -q package name command displays the package name, version, and release number of the installed package <package_name>. For example, using rpm -q tree to query installed package tree might generate the following output:
tree-1.5.2.2-4.el6.x86_64
man rpm for details) to further refine or qualify your query:
-a — queries all currently installed packages.
-f <file_name> — queries the RPM database for which package owns <file_name>rpm -qf /bin/ls instead of rpm -qf ls).
-p <package_file> — queries the uninstalled package <package_file>-i displays package information including name, description, release, size, build date, install date, vendor, and other miscellaneous information.
-l displays the list of files that the package contains.
-s displays the state of all the files in the package.
-d displays a list of files marked as documentation (man pages, info pages, READMEs, etc.) in the package.
-c displays a list of files marked as configuration files. These are the files you edit after installation to adapt and customize the package to your system (for example, sendmail.cf, passwd, inittab, etc.).
-v to the command to display the lists in a familiar ls -l format.
rpm -V verifies a package. You can use any of the Verify Options listed for querying to specify the packages you wish to verify. A simple use of verifying is rpm -V tree, which verifies that all the files in the tree package are as they were when they were originally installed. For example:
rpm -Vf /usr/bin/tree/usr/bin/tree is the absolute path to the file used to query a package.
rpm -Va
rpm -Vp tree-1.5.3-2.el6.x86_64.rpmc" denotes a configuration file) and then the file name. Each of the eight characters denotes the result of a comparison of one attribute of the file to the value of that attribute recorded in the RPM database. A single period (.) means the test passed. The following characters denote specific discrepancies:
5 — MD5 checksum
S — file size
L — symbolic link
T — file modification time
D — device
U — user
G — group
M — mode (includes permissions and file type)
? — unreadable file (file permission errors, for example)
<rpm_file> is the file name of the RPM package):
rpm -K --nosignature <rpm_file> <rpm_file>: rsa sha1 (md5) pgp md5 OK-K with -Kvv in the command.
x files as well.
rpm --import /usr/share/rhn/RPM-GPG-KEY
rpm -qa gpg-pubkey*gpg-pubkey-db42a60e-37ea5438
rpm -qi followed by the output from the previous command:
rpm -qi gpg-pubkey-db42a60e-37ea5438<rpm-file> with the file name of the RPM package):
rpm -K <rpm-file> md5 gpg OK. This means that the signature of the package has been verified, that it is not corrupt, and therefore is safe to install and use.
rpm -Va
rpm -qf /usr/bin/ghostscriptghostscript-8.70-1.el6.x86_64
/usr/bin/paste. You would like to verify the package that owns that program, but you do not know which package owns paste. Enter the following command,
rpm -Vf /usr/bin/paste
rpm -qdf /usr/bin/free/usr/share/doc/procps-3.2.8/BUGS /usr/share/doc/procps-3.2.8/FAQ /usr/share/doc/procps-3.2.8/NEWS /usr/share/doc/procps-3.2.8/TODO /usr/share/man/man1/free.1.gz /usr/share/man/man1/pgrep.1.gz /usr/share/man/man1/pkill.1.gz /usr/share/man/man1/pmap.1.gz /usr/share/man/man1/ps.1.gz /usr/share/man/man1/pwdx.1.gz /usr/share/man/man1/skill.1.gz /usr/share/man/man1/slabtop.1.gz /usr/share/man/man1/snice.1.gz /usr/share/man/man1/tload.1.gz /usr/share/man/man1/top.1.gz /usr/share/man/man1/uptime.1.gz /usr/share/man/man1/w.1.gz /usr/share/man/man1/watch.1.gz /usr/share/man/man5/sysctl.conf.5.gz /usr/share/man/man8/sysctl.8.gz /usr/share/man/man8/vmstat.8.gz
rpm -qip crontabs-1.10-32.1.el6.noarch.rpmName : crontabs Relocations: (not relocatable) Version : 1.10 Vendor: Red Hat, Inc. Release : 32.1.el6 Build Date: Thu 03 Dec 2009 02:17:44 AM CET Install Date: (not installed) Build Host: js20-bc1-11.build.redhat.com Group : System Environment/Base Source RPM: crontabs-1.10-32.1.el6.src.rpm Size : 2486 License: Public Domain and GPLv2 Signature : RSA/8, Wed 24 Feb 2010 08:46:13 PM CET, Key ID 938a80caf21541eb Packager : Red Hat, Inc. <http://bugzilla.redhat.com/bugzilla> Summary : Root crontab files used to schedule the execution of programs Description : The crontabs package contains root crontab files and directories. You will need to install cron daemon to run the jobs from the crontabs. The cron daemon such as cronie or fcron checks the crontab files to see when particular commands are scheduled to be executed. If commands are scheduled, it executes them. Crontabs handles a basic system function, so it should be installed on your system.
crontabs RPM package installs. You would enter the following:
rpm -qlp crontabs-1.10-32.1.el6.noarch.rpm/etc/cron.daily /etc/cron.hourly /etc/cron.monthly /etc/cron.weekly /etc/crontab /usr/bin/run-parts /usr/share/man/man4/crontabs.4.gz
rpm --help — This command displays a quick reference of RPM parameters.
man rpm — The RPM man page gives more detail about RPM parameters than the rpm --help command.
Xorg binary) listens for connections from X client applications via a network or local loopback interface. The server communicates with the hardware, such as the video card, monitor, keyboard, and mouse. X client applications exist in the user space, creating a graphical user interface (GUI) for the user and passing user requests to the X server.
evdev, that supports all input devices that the kernel knows about, including most mice and keyboards.
/usr/ directory. The /etc/X11/ directory contains configuration files for X client and server applications. This includes configuration files for the X server itself, the X display managers, and many other base components.
/etc/fonts/fonts.conf. For more information on configuring and adding fonts, refer to Section C.4, “Fonts”.
metacity kwin compiz compiz package.
mwm mwm) is a basic, stand-alone window manager. Since it is designed to be stand-alone, it should not be used in conjunction with GNOME or KDE. To run this window manager, you need to install the openmotif package.
twm twm), which provides the most basic tool set among the available window managers, can be used either as a stand-alone or with a desktop environment. To run this window manager, you need to install the xorg-x11-twm package.
/usr/bin/Xorg; a symbolic link X pointing to this file is also provided. Associated configuration files are stored in the /etc/X11/ and /usr/share/X11/ directories.
xorg.conf.d directory contain preconfigured settings from vendors and from distribution, and these files should not be edited by hand. Configuration in the xorg.conf file, on the other hand, is done completely by hand but is not necessary in most scenarios.
/etc/X11/xorg.conf, that was necessary in previous releases, is not supplied with the current release of the X Window System. It can still be useful to create the file manually to configure new hardware, to set up an environment with multiple video cards, or for debugging purposes.
/usr/lib/xorg/modules/ (or /usr/lib64/xorg/modules/) directory contains X server modules that can be loaded dynamically at runtime. By default, only some modules in /usr/lib/xorg/modules/ are automatically loaded by the X server.
mouse, kbd, or vmmouse driver configured in the xorg.conf file are, by default, ignored by the X server. Refer to Section C.3.3.3, “The ServerFlags section” for further details. Additional configuration is provided in the /etc/X11/xorg.conf.d/ directory and it can override or augment any configuration that has been obtained through HAL.
Section "section-name" line, where "section-name" is the title for the section, and ends with an EndSection line. Each section contains lines that include option names and one or more option values. Some of these are sometimes enclosed in double quotes (").
/etc/X11/xorg.conf file accept a boolean switch which turns the feature on or off. The acceptable values are:
1, on, true, or yes — Turns the option on.
0, off, false, or no — Turns the option off.
#) are not read by the X server and are used for human-readable comments.
# This file is autogenerated by system-setup-keyboard. Any # modifications will be lost. Section "InputClass" Identifier "system-setup-keyboard" MatchIsKeyboard "on" Option "XkbModel" "pc105" Option "XkbLayout" "cz,us" # Option "XkbVariant" "(null)" Option "XkbOptions" "terminate:ctrl_alt_bksp,grp:shifts_toggle,grp_led:scroll" EndSection
xorg.conf.d Directory/usr/share/X11/xorg.conf.d/ provides separate configuration files from vendors or third-party packages; changes to files in this directory may be overwritten by settings specified in the /etc/X11/xorg.conf file. The /etc/X11/xorg.conf.d/ directory stores user-specific configuration.
.conf in configuration directories are parsed by the X server upon startup and are treated like part of the traditional xorg.conf configuration file. These files may contain one or more sections; for a description of the options in a section and the general layout of the configuration file, refer to Section C.3.3, “The xorg.conf File” or to the xorg.conf(5) man page. The X server essentially treats the collection of configuration files as one big file with entries from xorg.conf at the end. Users are encouraged to put custom configuration into /etc/xorg.conf and leave the directory for configuration snippets provided by the distribution.
xorg.conf File/etc/X11/xorg.conf file was used to store initial setup for X. When a change occurred with the monitor, video card or other device managed by the X server, the file needed to be edited manually. In Red Hat Enterprise Linux, there is rarely a need to manually create and edit the /etc/X11/xorg.conf file. Nevertheless, it is still useful to understand various sections and optional parameters available, especially when troubleshooting or setting up unusual hardware configuration.
/etc/X11/xorg.conf file. More detailed information about the X server configuration file can be found in the xorg.conf(5) man page. This section is mostly intended for advanced users as most configuration options described below are not needed in typical configuration scenarios.
InputClass sectionInputClass is a new type of configuration section that does not apply to a single device but rather to a class of devices, including hot-plugged devices. An InputClass section's scope is limited by the matches specified; in order to apply to an input device, all matches must apply to the device as seen in the example below:
Section "InputClass" Identifier "touchpad catchall" MatchIsTouchpad "on" Driver "synaptics" EndSection
xorg.conf file or an xorg.conf.d directory, any touchpad present in the system is assigned the synaptics driver.
xorg.conf.dxorg.conf.d directory, the Driver setting in the example above overwrites previously set driver options. The more generic the class, the earlier it should be listed.
InputClass section:
MatchIsPointer, MatchIsKeyboard, MatchIsTouchpad, MatchIsTouchscreen, MatchIsJoystick — boolean options to specify a type of a device.
MatchProduct "product_name" — this option matches if the product_name substring occurs in the product name of the device.
MatchVendor "vendor_name" — this option matches if the vendor_name substring occurs in the vendor name of the device.
MatchDevicePath "/path/to/device" — this option matches any device if its device path corresponds to the patterns given in the "/path/to/device" template, for example /dev/input/event*. Refer to the fnmatch(3) man page for further details.
MatchTag "tag_pattern" — this option matches if at least one tag assigned by the HAL configuration back end matches the tag_pattern pattern.
InputClass sections. These sections are optional and are used to configure a class of input devices as they are automatically added. An input device can match more than one InputClass section. When arranging these sections, it is recommended to put generic matches above specific ones because each input class can override settings from a previous one if an overlap occurs.
InputDevice sectionInputDevice section configures one input device for the X server. Previously, systems typically had at least one InputDevice section for the keyboard, and most mouse settings were automatically detected.
InputDevice configuration is needed for most setups, and the xorg-x11-drv-* input driver packages provide the automatic configuration through HAL. The default driver for both keyboards and mice is evdev.
InputDevice section for a keyboard:
Section "InputDevice" Identifier "Keyboard0" Driver "kbd" Option "XkbModel" "pc105" Option "XkbLayout" "us" EndSection
InputDevice section:
Identifier — Specifies a unique name for this InputDevice section. This is a required entry.
Driver — Specifies the name of the device driver X must load for the device. If the AutoAddDevices option is enabled (which is the default setting), any input device section with Driver "mouse" or Driver "kbd" will be ignored. This is necessary due to conflicts between the legacy mouse and keyboard drivers and the new evdev generic driver. Instead, the server will use the information from the back end for any input devices. Any custom input device configuration in the xorg.conf should be moved to the back end. In most cases, the back end will be HAL and the configuration location will be the /etc/X11/xorg.conf.d directory.
Option — Specifies necessary options pertaining to the device.
xorg.conf file:
Protocol — Specifies the protocol used by the mouse, such as IMPS/2.
Device — Specifies the location of the physical device.
Emulate3Buttons — Specifies whether to allow a two-button mouse to act like a three-button mouse when both mouse buttons are pressed simultaneously.
xorg.conf(5) man page for a complete list of valid options for this section.
ServerFlags sectionServerFlags section contains miscellaneous global X server settings. Any settings in this section may be overridden by options placed in the ServerLayout section (refer to Section C.3.3.4, “ServerLayout” for details).
ServerFlags section occupies a single line and begins with the term Option followed by an option enclosed in double quotation marks (").
ServerFlags section:
Section "ServerFlags" Option "DontZap" "true" EndSection
"DontZap" "boolean" — When the value of <boolean> is set to true, this setting prevents the use of the Ctrl+Alt+Backspace key combination to immediately terminate the X server.
setxkbmap -option "terminate:ctrl_alt_bksp""DontZoom" "boolean" — When the value of <boolean> is set to true, this setting prevents cycling through configured video resolutions using the Ctrl+Alt+Keypad-Plus and Ctrl+Alt+Keypad-Minus key combinations.
"AutoAddDevices" "boolean" — When the value of <boolean> is set to false, the server will not hot plug input devices and instead rely solely on devices configured in the xorg.conf file. Refer to Section C.3.3.2, “The InputDevice section” for more information concerning input devices. This option is enabled by default and HAL (hardware abstraction layer) is used as a back end for device discovery.
ServerLayoutServerLayout section binds together the input and output devices controlled by the X server. At a minimum, this section must specify one input device and one output device. By default, a monitor (output device) and a keyboard (input device) are specified.
ServerLayout section:
Section "ServerLayout" Identifier "Default Layout" Screen 0 "Screen0" 0 0 InputDevice "Mouse0" "CorePointer" InputDevice "Keyboard0" "CoreKeyboard" EndSection
ServerLayout section:
Identifier — Specifies a unique name for this ServerLayout section.
Screen — Specifies the name of a Screen section to be used with the X server. More than one Screen option may be present.
Screen entry:
Screen 0 "Screen0" 0 0
Screen entry (0) indicates that the first monitor connector, or head on the video card, uses the configuration specified in the Screen section with the identifier "Screen0".
Screen section with the identifier "Screen0" can be found in Section C.3.3.8, “The Screen section”.
Screen entry with a different number and a different Screen section identifier is necessary.
"Screen0" give the absolute X and Y coordinates for the upper left corner of the screen (0 0 by default).
InputDevice — Specifies the name of an InputDevice section to be used with the X server.
InputDevice entries: one for the default mouse and one for the default keyboard. The options CorePointer and CoreKeyboard indicate that these are the primary mouse and keyboard. If the AutoAddDevices option is enabled, this entry needs not to be specified in the ServerLayout section. If the AutoAddDevices option is disabled, both mouse and keyboard are auto-detected with the default values.
Option "option-name" — An optional entry which specifies extra parameters for the section. Any options listed here override those listed in the ServerFlags section.
<option-name> with a valid option listed for this section in the xorg.conf(5) man page.
ServerLayout section in the /etc/X11/xorg.conf file. By default, the server only reads the first one it encounters, however. If there is an alternative ServerLayout section, it can be specified as a command line argument when starting an X session; as in the Xorg -layout <layoutname> command.
Files sectionFiles section sets paths for services vital to the X server, such as the font path. This is an optional section, as these paths are normally detected automatically. This section can be used to override automatically detected values.
Files section:
Section "Files" RgbPath "/usr/share/X11/rgb.txt" FontPath "unix/:7100" EndSection
Files section:
ModulePath — An optional parameter which specifies alternate directories which store X server modules.
Monitor sectionMonitor section configures one type of monitor used by the system. This is an optional entry as most monitors are now detected automatically.
Monitor section for a monitor:
Section "Monitor" Identifier "Monitor0" VendorName "Monitor Vendor" ModelName "DDC Probed Monitor - ViewSonic G773-2" DisplaySize 320 240 HorizSync 30.0 - 70.0 VertRefresh 50.0 - 180.0 EndSection
Monitor section:
Identifier — Specifies a unique name for this Monitor section. This is a required entry.
VendorName — An optional parameter which specifies the vendor of the monitor.
ModelName — An optional parameter which specifies the monitor's model name.
DisplaySize — An optional parameter which specifies, in millimeters, the physical size of the monitor's picture area.
HorizSync — Specifies the range of horizontal sync frequencies compatible with the monitor, in kHz. These values help the X server determine the validity of built-in or specified Modeline entries for the monitor.
VertRefresh — Specifies the range of vertical refresh frequencies supported by the monitor, in kHz. These values help the X server determine the validity of built-in or specified Modeline entries for the monitor.
Modeline — An optional parameter which specifies additional video modes for the monitor at particular resolutions, with certain horizontal sync and vertical refresh resolutions. Refer to the xorg.conf(5) man page for a more detailed explanation of Modeline entries.
Option "option-name" — An optional entry which specifies extra parameters for the section. Replace <option-name> with a valid option listed for this section in the xorg.conf(5) man page.
Device sectionDevice section configures one video card on the system. While one Device section is the minimum, additional instances may occur for each video card installed on the machine.
Device section for a video card:
Section "Device" Identifier "Videocard0" Driver "mga" VendorName "Videocard vendor" BoardName "Matrox Millennium G200" VideoRam 8192 Option "dpms" EndSection
Device section:
Identifier — Specifies a unique name for this Device section. This is a required entry.
Driver — Specifies which driver the X server must load to utilize the video card. A list of drivers can be found in /usr/share/hwdata/videodrivers, which is installed with the hwdata package.
VendorName — An optional parameter which specifies the vendor of the video card.
BoardName — An optional parameter which specifies the name of the video card.
VideoRam — An optional parameter which specifies the amount of RAM available on the video card, in kilobytes. This setting is only necessary for video cards the X server cannot probe to detect the amount of video RAM.
BusID — An entry which specifies the bus location of the video card. On systems with only one video card a BusID entry is optional and may not even be present in the default /etc/X11/xorg.conf file. On systems with more than one video card, however, a BusID entry is required.
Screen — An optional entry which specifies which monitor connector or head on the video card the Device section configures. This option is only useful for video cards with multiple heads.
Device sections must exist and each of these sections must have a different Screen value.
Screen entry must be an integer. The first head on the video card has a value of 0. The value for each additional head increments this value by one.
Option "option-name" — An optional entry which specifies extra parameters for the section. Replace <option-name> with a valid option listed for this section in the xorg.conf(5) man page.
"dpms" (for Display Power Management Signaling, a VESA standard), which activates the Service Star energy compliance setting for the monitor.
Screen sectionScreen section binds one video card (or video card head) to one monitor by referencing the Device section and the Monitor section for each. While one Screen section is the minimum, additional instances may occur for each video card and monitor combination present on the machine.
Screen section:
Section "Screen"
Identifier "Screen0"
Device "Videocard0"
Monitor "Monitor0"
DefaultDepth 16
SubSection "Display"
Depth 24
Modes "1280x1024" "1280x960" "1152x864" "1024x768" "800x600" "640x480"
EndSubSection
SubSection "Display"
Depth 16
Modes "1152x864" "1024x768" "800x600" "640x480"
EndSubSection
EndSectionScreen section:
Identifier — Specifies a unique name for this Screen section. This is a required entry.
Device — Specifies the unique name of a Device section. This is a required entry.
Monitor — Specifies the unique name of a Monitor section. This is only required if a specific Monitor section is defined in the xorg.conf file. Normally, monitors are detected automatically.
DefaultDepth — Specifies the default color depth in bits. In the previous example, 16 (which provides thousands of colors) is the default. Only one DefaultDepth entry is permitted, although this can be overridden with the Xorg command line option -depth <n>, where <n>SubSection "Display" — Specifies the screen modes available at a particular color depth. The Screen section can have multiple Display subsections, which are entirely optional since screen modes are detected automatically.
Option "option-name" — An optional entry which specifies extra parameters for the section. Replace <option-name> with a valid option listed for this section in the xorg.conf(5) man page.
DRI sectionDRI section specifies parameters for the Direct Rendering Infrastructure (DRI). DRI is an interface which allows 3D software applications to take advantage of 3D hardware acceleration capabilities built into most modern video hardware. In addition, DRI can improve 2D performance via hardware acceleration, if supported by the video card driver.
xorg.conf file will override the default values.
DRI section:
Section "DRI" Group 0 Mode 0666 EndSection
Qt 3 or GTK+ 2 graphical toolkits, or their newer versions.
/etc/fonts/fonts.conf configuration file, which should not be edited by hand.
fonts group installed. This can be done by selecting the group in the installer, and also by running the yum groupinstall fonts command after installation.
.fonts/ directory in the user's home directory.
/usr/share/fonts/ directory. It is a good idea to create a new subdirectory, such as local/ or similar, to help distinguish between user-installed and default fonts.
fc-cache command as root to update the font information cache:
fc-cache <path-to-font-directory><path-to-font-directory> with the directory containing the new fonts (either /usr/share/fonts/local/ or /home/<user>/.fonts/).
fonts:/// into the Nautilus address bar, and dragging the new font files there.
startx. The startx command is a front-end to the xinit command, which launches the X server (Xorg) and connects X client applications to it. Because the user is already logged into the system at runlevel 3, startx does not launch a display manager or authenticate users. Refer to Section C.5.2, “Runlevel 5” for more information about display managers.
startx command is executed, it searches for the .xinitrc file in the user's home directory to define the desktop environment and possibly other X client applications to run. If no .xinitrc file is present, it uses the system default /etc/X11/xinit/xinitrc file instead.
xinitrc script then searches for user-defined files and default system files, including .Xresources, .Xmodmap, and .Xkbmap in the user's home directory, and Xresources, Xmodmap, and Xkbmap in the /etc/X11/ directory. The Xmodmap and Xkbmap files, if they exist, are used by the xmodmap utility to configure the keyboard. The Xresources file is read to assign specific preference values to applications.
xinitrc script executes all scripts located in the /etc/X11/xinit/xinitrc.d/ directory. One important script in this directory is xinput.sh, which configures settings such as the default language.
xinitrc script attempts to execute .Xclients in the user's home directory and turns to /etc/X11/xinit/Xclients if it cannot be found. The purpose of the Xclients file is to start the desktop environment or, possibly, just a basic window manager. The .Xclients script in the user's home directory starts the user-specified desktop environment in the .Xclients-default file. If .Xclients does not exist in the user's home directory, the standard /etc/X11/xinit/Xclients script attempts to start another desktop environment, trying GNOME first, then KDE, followed by twm.
GDM (GNOME Display Manager) — The default display manager for Red Hat Enterprise Linux. GNOME allows the user to configure language settings, shutdown, restart or log in to the system.
KDM — KDE's display manager which allows the user to shutdown, restart or log in to the system.
xdm (X Window Display Manager) — A very basic display manager which only lets the user log in to the system.
/etc/X11/prefdm script determines the preferred display manager by referencing the /etc/sysconfig/desktop file. A list of options for this file is available in this file:
/usr/share/doc/initscripts-<version-number>/sysconfig.txt<version-number> is the version number of the initscripts package.
/etc/X11/xdm/Xsetup_0 file to set up the login screen. Once the user logs into the system, the /etc/X11/xdm/GiveConsole script runs to assign ownership of the console to the user. Then, the /etc/X11/xdm/Xsession script runs to accomplish many of the tasks normally performed by the xinitrc script when starting X from runlevel 3, including setting system and user resources, as well as running the scripts in the /etc/X11/xinit/xinitrc.d/ directory.
GNOME or KDE display managers by selecting it from the menu item accessed by selecting → → → . If the desktop environment is not specified in the display manager, the /etc/X11/xdm/Xsession script checks the .xsession and .Xclients files in the user's home directory to decide which desktop environment to load. As a last resort, the /etc/X11/xinit/Xclients file is used to select a desktop environment or window manager to use in the same way as runlevel 3.
:0) and logs out, the /etc/X11/xdm/TakeConsole script runs and reassigns ownership of the console to the root user. The original display manager, which continues running after the user logged in, takes control by spawning a new display manager. This restarts the X server, displays a new login window, and starts the entire process over again.
/usr/share/doc/gdm-<version-number>/README, where <version-number> is the version number for the gdm package installed, or the xdm man page.
/usr/share/X11/doc/ — contains detailed documentation on the X Window System architecture, as well as how to get additional information about the Xorg project as a new user.
/usr/share/doc/gdm-<version-number>/README — contains information on how display managers control user authentication.
man xorg.conf — Contains information about the xorg.conf configuration files, including the meaning and syntax for the different sections within the files.
man Xorg — Describes the Xorg display server.
/etc/sysconfig/ directory, their function, and their contents. The information in this appendix is not intended to be complete, as many of these files have a variety of options that are only used in very specific or rare circumstances.
/etc/sysconfig/ directory depends on the programs you have installed on your machine. To find the name of the package the configuration file belongs to, type the following at a shell prompt:
~]$ yum provides /etc/sysconfig/filename /etc/sysconfig/ directory.
/etc/sysconfig/arpwatch file is used to pass arguments to the arpwatch daemon at boot time. By default, it contains the following option:
OPTIONS=value arpwatch daemon. For example:
OPTIONS="-u arpwatch -e root -s 'root (Arpwatch)'"
/etc/sysconfig/authconfig file sets the authorization to be used on the host. By default, it contains the following options:
USEMKHOMEDIR=boolean yes) or disable (no) creating a home directory for a user on the first login. For example:
USEMKHOMEDIR=no
USEPAMACCESS=boolean yes) or disable (no) the PAM authentication. For example:
USEPAMACCESS=no
USESSSDAUTH=boolean yes) or disable (no) the SSSD authentication. For example:
USESSSDAUTH=no
USESHADOW=boolean yes) or disable (no) shadow passwords. For example:
USESHADOW=yes
USEWINBIND=boolean yes) or disable (no) using Winbind for user account configuration. For example:
USEWINBIND=no
USEDB=boolean yes) or disable (no) the FAS authentication. For example:
USEDB=no
USEFPRINTD=boolean yes) or disable (no) the fingerprint authentication. For example:
USEFPRINTD=yes
FORCESMARTCARD=boolean yes) or disable (no) enforcing the smart card authentication. For example:
FORCESMARTCARD=no
PASSWDALGORITHM=value value can be bigcrypt, descrypt, md5, sha256, or sha512. For example:
PASSWDALGORITHM=sha512
USELDAPAUTH=boolean yes) or disable (no) the LDAP authentication. For example:
USELDAPAUTH=no
USELOCAUTHORIZE=boolean yes) or disable (no) the local authorization for local users. For example:
USELOCAUTHORIZE=yes
USECRACKLIB=boolean yes) or disable (no) using the CrackLib. For example:
USECRACKLIB=yes
USEWINBINDAUTH=boolean yes) or disable (no) the Winbind authentication. For example:
USEWINBINDAUTH=no
USESMARTCARD=boolean yes) or disable (no) the smart card authentication. For example:
USESMARTCARD=no
USELDAP=boolean yes) or disable (no) using LDAP for user account configuration. For example:
USELDAP=no
USENIS=boolean yes) or disable (no) using NIS for user account configuration. For example:
USENIS=no
USEKERBEROS=boolean yes) or disable (no) the Kerberos authentication. For example:
USEKERBEROS=no
USESYSNETAUTH=boolean yes) or disable (no) authenticating system accounts with network services. For example:
USESYSNETAUTH=no
USESMBAUTH=boolean yes) or disable (no) the SMB authentication. For example:
USESMBAUTH=no
USESSSD=boolean yes) or disable (no) using SSSD for obtaining user information. For example:
USESSSD=no
USEHESIOD=boolean yes) or disable (no) using the Hesoid name service. For example:
USEHESIOD=no
/etc/sysconfig/autofs file defines custom options for the automatic mounting of devices. This file controls the operation of the automount daemons, which automatically mount file systems when you use them and unmount them after a period of inactivity. File systems can include network file systems, CD-ROM drives, diskettes, and other media.
MASTER_MAP_NAME=value MASTER_MAP_NAME="auto.master"
TIMEOUT=value TIMEOUT=300
NEGATIVE_TIMEOUT=value NEGATIVE_TIMEOUT=60
MOUNT_WAIT=value mount. For example:
MOUNT_WAIT=-1
UMOUNT_WAIT=value umount. For example:
UMOUNT_WAIT=12
BROWSE_MODE=boolean yes) or disable (no) browsing the maps. For example:
BROWSE_MODE="no"
MOUNT_NFS_DEFAULT_PROTOCOL=value mount.nfs. For example:
MOUNT_NFS_DEFAULT_PROTOCOL=4
APPEND_OPTIONS=boolean yes) or disable (no) appending the global options instead of replacing them. For example:
APPEND_OPTIONS="yes"
LOGGING=value value has to be either none, verbose, or debug. For example:
LOGGING="none"
LDAP_URI=value protocol://serverLDAP_URI="ldaps://ldap.example.com/"
LDAP_TIMEOUT=value LDAP_TIMEOUT=-1
LDAP_NETWORK_TIMEOUT=value LDAP_NETWORK_TIMEOUT=8
SEARCH_BASE=value SEARCH_BASE=""
AUTH_CONF_FILE=value AUTH_CONF_FILE="/etc/autofs_ldap_auth.conf"
MAP_HASH_TABLE_SIZE=value MAP_HASH_TABLE_SIZE=1024
USE_MISC_DEVICE=boolean yes) or disable (no) using the autofs miscellaneous device. For example:
USE_MISC_DEVICE="yes"
OPTIONS=value OPTIONS=""
/etc/sysconfig/clock file controls the interpretation of values read from the system hardware clock. It is used by the Date/Time Properties tool, and should not be edited by hand. By default, it contains the following option:
ZONE=value /usr/share/zoneinfo that /etc/localtime is a copy of. For example:
ZONE="Europe/Prague"
/etc/sysconfig/dhcpd file is used to pass arguments to the dhcpd daemon at boot time. By default, it contains the following options:
DHCPDARGS=value dhcpd daemon. For example:
DHCPDARGS=
/etc/sysconfig/firstboot file defines whether to run the firstboot utility. By default, it contains the following option:
RUN_FIRSTBOOT=boolean YES) or disable (NO) running the firstboot program. For example:
RUN_FIRSTBOOT=NO
init program calls the /etc/rc.d/init.d/firstboot script, which looks for the /etc/sysconfig/firstboot file. If this file does not contain the RUN_FIRSTBOOT=NO option, the firstboot program is run, guiding a user through the initial configuration of the system.
firstboot program the next time the system boots, change the value of RUN_FIRSTBOOT option to YES, and type the following at a shell prompt:
~]# chkconfig firstboot on/etc/sysconfig/i18n configuration file defines the default language, any supported languages, and the default system font. By default, it contains the following options:
LANG=value LANG="en_US.UTF-8"
SUPPORTED=value SUPPORTED="en_US.UTF-8:en_US:en"
SYSFONT=value SYSFONT="latarcyrheb-sun16"
/etc/sysconfig/init file controls how the system appears and functions during the boot process. By default, it contains the following options:
BOOTUP=value color (the standard color boot display), verbose (an old style display which provides more information), or anything else for the new style display, but without ANSI formatting. For example:
BOOTUP=color
RES_COL=value RES_COL=60
MOVE_TO_COL=value RES_COL (see above). For example:
MOVE_TO_COL="echo -en \\033[${RES_COL}G"SETCOLOR_SUCCESS=value SETCOLOR_SUCCESS="echo -en \\033[0;32m"
SETCOLOR_FAILURE=value SETCOLOR_FAILURE="echo -en \\033[0;31m"
SETCOLOR_WARNING=value SETCOLOR_WARNING="echo -en \\033[0;33m"
SETCOLOR_NORMAL=value SETCOLOR_NORMAL="echo -en \\033[0;39m"
LOGLEVEL=value value has to be in the range from 1 (kernel panics only) to 8 (everything, including the debugging information). For example:
LOGLEVEL=3
PROMPT=boolean yes) or disable (no) the hotkey interactive startup. For example:
PROMPT=yes
AUTOSWAP=boolean yes) or disable (no) probing for devices with swap signatures. For example:
AUTOSWAP=no
ACTIVE_CONSOLES=value ACTIVE_CONSOLES=/dev/tty[1-6]
SINGLE=value value has to be either /sbin/sulogin (a user will be prompted for a password to log in), or /sbin/sushell (the user will be logged in directly). For example:
SINGLE=/sbin/sushell
/etc/sysconfig/ip6tables-config file stores information used by the kernel to set up IPv6 packet filtering at boot time or whenever the ip6tables service is started. Note that you should not modify it unless you are familiar with ip6tables rules. By default, it contains the following options:
IP6TABLES_MODULES=value IP6TABLES_MODULES="ip_nat_ftp ip_nat_irc"
IP6TABLES_MODULES_UNLOAD=boolean yes) or disable (no) module unloading when the firewall is stopped or restarted. For example:
IP6TABLES_MODULES_UNLOAD="yes"
IP6TABLES_SAVE_ON_STOP=boolean yes) or disable (no) saving the current firewall rules when the firewall is stopped. For example:
IP6TABLES_SAVE_ON_STOP="no"
IP6TABLES_SAVE_ON_RESTART=boolean yes) or disable (no) saving the current firewall rules when the firewall is restarted. For example:
IP6TABLES_SAVE_ON_RESTART="no"
IP6TABLES_SAVE_COUNTER=boolean yes) or disable (no) saving the rule and chain counters. For example:
IP6TABLES_SAVE_COUNTER="no"
IP6TABLES_STATUS_NUMERIC=boolean yes) or disable (no) printing IP addresses and port numbers in a numeric format in the status output. For example:
IP6TABLES_STATUS_NUMERIC="yes"
IP6TABLES_STATUS_VERBOSE=boolean yes) or disable (no) printing information about the number of packets and bytes in the status output. For example:
IP6TABLES_STATUS_VERBOSE="no"
IP6TABLES_STATUS_LINENUMBERS=boolean yes) or disable (no) printing line numbers in the status output. For example:
IP6TABLES_STATUS_LINENUMBERS="yes"
ip6tables command. Once created, type the following at a shell prompt:
~]# service ip6tables save/etc/sysconfig/ip6tables. Once this file exists, any firewall rules saved in it persist through a system reboot or a service restart.
/etc/sysconfig/keyboard file controls the behavior of the keyboard. By default, it contains the following options:
KEYTABLE=value /lib/kbd/keymaps/i386/ directory, and branch into different keyboard layouts from there, all labeled value.kmap.gzKEYTABLE setting is used. For example:
KEYTABLE="us"
MODEL=value MODEL="pc105+inet"
LAYOUT=value LAYOUT="us"
KEYBOARDTYPE=value pc (a PS/2 keyboard), or sun (a Sun keyboard). For example:
KEYBOARDTYPE="pc"
/etc/sysconfig/ldap file holds the basic configuration for the LDAP server. By default, it contains the following options:
SLAPD_OPTIONS=value slapd daemon. For example:
SLAPD_OPTIONS="-4"
SLURPD_OPTIONS=value slurpd daemon. For example:
SLURPD_OPTIONS=""
SLAPD_LDAP=boolean yes) or disable (no) using the LDAP over TCP (that is, ldap:///). For example:
SLAPD_LDAP="yes"
SLAPD_LDAPI=boolean yes) or disable (no) using the LDAP over IPC (that is, ldapi:///). For example:
SLAPD_LDAPI="no"
SLAPD_LDAPS=boolean yes) or disable (no) using the LDAP over TLS (that is, ldaps:///). For example:
SLAPD_LDAPS="no"
SLAPD_URLS=value SLAPD_URLS="ldapi:///var/lib/ldap_root/ldapi ldapi:/// ldaps:///"
SLAPD_SHUTDOWN_TIMEOUT=value slapd to shut down. For example:
SLAPD_SHUTDOWN_TIMEOUT=3
SLAPD_ULIMIT_SETTINGS=value ulimit before the slapd daemon is started. For example:
SLAPD_ULIMIT_SETTINGS=""
/etc/sysconfig/named file is used to pass arguments to the named daemon at boot time. By default, it contains the following options:
ROOTDIR=value named daemon runs. The value has to be a full directory path. For example:
ROOTDIR="/var/named/chroot"
info chroot at a shell prompt for more information).
OPTIONS=value named. For example:
OPTIONS="-6"
-t option. Instead, use ROOTDIR as described above.
KEYTAB_FILE=value KEYTAB_FILE="/etc/named.keytab"
/etc/sysconfig/network file is used to specify information about the desired network configuration. By default, it contains the following options:
NETWORKING=boolean yes) or disable (no) the networking. For example:
NETWORKING=yes
HOSTNAME=value HOSTNAME=penguin.example.com
GATEWAY=value GATEWAY=192.168.1.0
/etc/sysconfig/ntpd file is used to pass arguments to the ntpd daemon at boot time. By default, it contains the following option:
OPTIONS=value ntpd. For example:
OPTIONS="-u ntp:ntp -p /var/run/ntpd.pid -g"
ntpd daemon.
/etc/sysconfig/quagga file holds the basic configuration for Quagga daemons. By default, it contains the following options:
QCONFDIR=value QCONFDIR="/etc/quagga"
BGPD_OPTS=value bgpd daemon. For example:
BGPD_OPTS="-A 127.0.0.1 -f ${QCONFDIR}/bgpd.conf"OSPF6D_OPTS=value ospf6d daemon. For example:
OSPF6D_OPTS="-A ::1 -f ${QCONFDIR}/ospf6d.conf"OSPFD_OPTS=value ospfd daemon. For example:
OSPFD_OPTS="-A 127.0.0.1 -f ${QCONFDIR}/ospfd.conf"RIPD_OPTS=value ripd daemon. For example:
RIPD_OPTS="-A 127.0.0.1 -f ${QCONFDIR}/ripd.conf"RIPNGD_OPTS=value ripngd daemon. For example:
RIPNGD_OPTS="-A ::1 -f ${QCONFDIR}/ripngd.conf"ZEBRA_OPTS=value zebra daemon. For example:
ZEBRA_OPTS="-A 127.0.0.1 -f ${QCONFDIR}/zebra.conf"ISISD_OPTS=value isisd daemon. For example:
ISISD_OPTS="-A ::1 -f ${QCONFDIR}/isisd.conf"WATCH_OPTS=value watchquagga daemon. For example:
WATCH_OPTS="-Az -b_ -r/sbin/service_%s_restart -s/sbin/service_%s_start -k/sbin/service_%s_stop"
WATCH_DAEMONS=value WATCH_DAEMONS="zebra bgpd ospfd ospf6d ripd ripngd"
/etc/sysconfig/radvd file is used to pass arguments to the radvd daemon at boot time. By default, it contains the following option:
OPTIONS=value radvd daemon. For example:
OPTIONS="-u radvd"
/etc/sysconfig/samba file is used to pass arguments to the Samba daemons at boot time. By default, it contains the following options:
SMBDOPTIONS=value smbd. For example:
SMBDOPTIONS="-D"
NMBDOPTIONS=value nmbd. For example:
NMBDOPTIONS="-D"
WINBINDOPTIONS=value winbindd. For example:
WINBINDOPTIONS=""
/etc/sysconfig/selinux file contains the basic configuration options for SELinux. It is a symbolic link to /etc/selinux/config, and by default, it contains the following options:
SELINUX=value value can be either enforcing (the security policy is always enforced), permissive (instead of enforcing the policy, appropriate warnings are displayed), or disabled (no policy is used). For example:
SELINUX=enforcing
SELINUXTYPE=value value can be either targeted (the targeted processes are protected), or mls (the Multi Level Security protection). For example:
SELINUXTYPE=targeted
/etc/sysconfig/sendmail is used to set the default values for the Sendmail application. By default, it contains the following values:
DAEMON=boolean yes) or disable (no) running sendmail as a daemon. For example:
DAEMON=yes
QUEUE=value QUEUE=1h
/etc/sysconfig/spamassassin file is used to pass arguments to the spamd daemon (a daemonized version of Spamassassin) at boot time. By default, it contains the following option:
SPAMDOPTIONS=value spamd daemon. For example:
SPAMDOPTIONS="-d -c -m5 -H"
/etc/sysconfig/squid file is used to pass arguments to the squid daemon at boot time. By default, it contains the following options:
SQUID_OPTS=value squid daemon. For example:
SQUID_OPTS=""
SQUID_SHUTDOWN_TIMEOUT=value squid daemon to shut down. For example:
SQUID_SHUTDOWN_TIMEOUT=100
SQUID_CONF=value SQUID_CONF="/etc/squid/squid.conf"
/etc/sysconfig/system-config-users file is the configuration file for the User Manager utility, and should not be edited by hand. By default, it contains the following options:
FILTER=boolean true) or disable (false) filtering of system users. For example:
FILTER=true
ASSIGN_HIGHEST_UID=boolean true) or disable (false) assigning the highest available UID to newly added users. For example:
ASSIGN_HIGHEST_UID=true
ASSIGN_HIGHEST_GID=boolean true) or disable (false) assigning the highest available GID to newly added groups. For example:
ASSIGN_HIGHEST_GID=true
PREFER_SAME_UID_GID=boolean true) or disable (false) using the same UID and GID for newly added users when possible. For example:
PREFER_SAME_UID_GID=true
/etc/sysconfig/vncservers file configures the way the Virtual Network Computing (VNC) server starts up. By default, it contains the following options:
VNCSERVERS=value display:username VNCSERVERS="2:myusername"
VNCSERVERARGS[display]=value display. For example:
VNCSERVERARGS[2]="-geometry 800x600 -nolisten tcp -localhost"
/etc/sysconfig/xinetd file is used to pass arguments to the xinetd daemon at boot time. By default, it contains the following options:
EXTRAOPTIONS=value xinetd. For example:
EXTRAOPTIONS=""
XINETD_LANG=value xinetd. Note that to remove locale information from the xinetd environment, you can use an empty string ("") or none. For example:
XINETD_LANG="en_US"
xinetd services.
/etc/sysconfig/.
/etc/sysconfig/cbq/ /etc/sysconfig/networking/ system-config-network), and its contents should not be edited manually. For more information about configuring network interfaces using the Network Administration Tool, refer to Chapter 7, NetworkManager.
/etc/sysconfig/network-scripts/ ifcfg-eth0 for the eth0 Ethernet interface.
ifup and ifdown.
ifup-isdn and ifdown-isdn.
/etc/sysconfig/network-scripts/ directory, refer to Chapter 8, Network Interfaces.
/etc/sysconfig/rhn/ /proc/ directory (also called the proc file system) contains a hierarchy of special files which represent the current state of the kernel, allowing applications and users to peer into the kernel's view of the system.
/proc/ directory contains a wealth of information detailing system hardware and any running processes. In addition, some of the files within /proc/ can be manipulated by users and applications to communicate configuration changes to the kernel.
/proc/ide/ and /proc/pci/ directories obsolete. The /proc/ide/ file system is now superseded by files in sysfs; to retrieve information on PCI devices, use lspci instead. For more information on sysfs or lspci, refer to their respective man pages.
/proc/ directory contains another type of file called a virtual file. As such, /proc/ is often referred to as a virtual file system.
/proc/interrupts, /proc/meminfo, /proc/mounts, and /proc/partitions provide an up-to-the-moment glimpse of the system's hardware. Others, like the /proc/filesystems file and the /proc/sys/ directory provide system configuration information and interfaces.
/proc/ files operate similarly to text files, storing useful system and hardware data in human-readable text format. As such, you can use cat, more, or less to view them. For example, to display information about the system's CPU, run cat /proc/cpuinfo. This will return output similar to the following:
processor : 0 vendor_id : AuthenticAMD cpu family : 5 model : 9 model name : AMD-K6(tm) 3D+ Processor stepping : 1 cpu MHz : 400.919 cache size : 256 KB fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 1 wp : yes flags : fpu vme de pse tsc msr mce cx8 pge mmx syscall 3dnow k6_mtrr bogomips : 799.53
/proc/ contain information that is not human-readable. To retrieve information from such files, use tools such as lspci, apm, free, and top.
/proc/ directory are readable only by the root user.
/proc/ directory are read-only. However, some can be used to adjust settings in the kernel. This is especially true for files in the /proc/sys/ subdirectory.
echo value > /proc/file
echo www.example.com > /proc/sys/kernel/hostname
cat /proc/sys/net/ipv4/ip_forward returns either a 0 (off or false) or a 1 (on or true). A 0 indicates that the kernel is not forwarding network packets. To turn packet forwarding on, run echo 1 > /proc/sys/net/ipv4/ip_forward.
/proc/sys/ subdirectory is /sbin/sysctl. For more information on this command, refer to Section E.4, “Using the sysctl Command”
/proc/sys/ subdirectory, refer to Section E.3.9, “/proc/sys/”.
proc File System/proc/ directory.
DMA row references the first 16 MB on a system, the HighMem row references all memory greater than 4 GB on a system, and the Normal row references all memory in between.
/proc/buddyinfo:
Node 0, zone DMA 90 6 2 1 1 ... Node 0, zone Normal 1650 310 5 0 0 ... Node 0, zone HighMem 2 0 0 1 1 ...
/proc/cmdline file looks like the following:
ro root=/dev/VolGroup00/LogVol00 rhgb quiet 3
(ro)), located on the first logical volume (LogVol00) of the first volume group (/dev/VolGroup00). LogVol00 is the equivalent of a disk partition in a non-LVM system (Logical Volume Management), just as /dev/VolGroup00 is similar in concept to /dev/hda1, but much more extensible.
rhgb signals that the rhgb package has been installed, and graphical booting is supported, assuming /etc/inittab shows a default runlevel set to id:5:initdefault:.
quiet indicates all verbose kernel messages are suppressed at boot time.
/proc/cpuinfo:
processor : 0 vendor_id : GenuineIntel cpu family : 15 model : 2 model name : Intel(R) Xeon(TM) CPU 2.40GHz stepping : 7 cpu MHz : 2392.371 cache size : 512 KB physical id : 0 siblings : 2 runqueue : 0 fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 2 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm bogomips : 4771.02
processor — Provides each processor with an identifying number. On systems that have one processor, only a 0 is present.
cpu family — Authoritatively identifies the type of processor in the system. For an Intel-based system, place the number in front of "86" to determine the value. This is particularly helpful for those attempting to identify the architecture of an older system such as a 586, 486, or 386. Because some RPM packages are compiled for each of these particular architectures, this value also helps users determine which packages to install.
model name — Displays the common name of the processor, including its project name.
cpu MHz — Shows the precise speed in megahertz for the processor to the thousandths decimal place.
cache size — Displays the amount of level 2 memory cache available to the processor.
siblings — Displays the number of sibling CPUs on the same physical CPU for architectures which use hyper-threading.
flags — Defines a number of different qualities about the processor, such as the presence of a floating point unit (FPU) and the ability to process MMX instructions.
/proc/crypto file looks like the following:
name : sha1 module : kernel type : digest blocksize : 64 digestsize : 20 name : md5 module : md5 type : digest blocksize : 64 digestsize : 16
Character devices: 1 mem 4 /dev/vc/0 4 tty 4 ttyS 5 /dev/tty 5 /dev/console 5 /dev/ptmx 7 vcs 10 misc 13 input 29 fb 36 netlink 128 ptm 136 pts 180 usb Block devices: 1 ramdisk 3 ide0 9 md 22 ide1 253 device-mapper 254 mdp
/proc/devices includes the major number and name of the device, and is broken into two major sections: Character devices and Block devices.
/usr/share/doc/kernel-doc-<kernel_version>/Documentation/devices.txt/proc/dma files looks like the following:
4: cascade
0-0 Linux [kernel]
PER_LINUX execution domain, different personalities can be implemented as dynamically loadable modules.
/proc/fb for systems which contain frame buffer devices looks similar to the following:
0 VESA VGA
/proc/filesystems file looks similar to the following:
nodev sysfs nodev rootfs nodev bdev nodev proc nodev sockfs nodev binfmt_misc nodev usbfs nodev usbdevfs nodev futexfs nodev tmpfs nodev pipefs nodev eventpollfs nodev devpts ext2 nodev ramfs nodev hugetlbfs iso9660 nodev mqueue ext3 nodev rpc_pipefs nodev autofs
nodev are not mounted on a device. The second column lists the names of the file systems supported.
mount command cycles through the file systems listed here when one is not specified as an argument.
/proc/interrupts looks similar to the following:
CPU0 0: 80448940 XT-PIC timer 1: 174412 XT-PIC keyboard 2: 0 XT-PIC cascade 8: 1 XT-PIC rtc 10: 410964 XT-PIC eth0 12: 60330 XT-PIC PS/2 Mouse 14: 1314121 XT-PIC ide0 15: 5195422 XT-PIC ide1 NMI: 0 ERR: 0
CPU0 CPU1 0: 1366814704 0 XT-PIC timer 1: 128 340 IO-APIC-edge keyboard 2: 0 0 XT-PIC cascade 8: 0 1 IO-APIC-edge rtc 12: 5323 5793 IO-APIC-edge PS/2 Mouse 13: 1 0 XT-PIC fpu 16: 11184294 15940594 IO-APIC-level Intel EtherExpress Pro 10/100 Ethernet 20: 8450043 11120093 IO-APIC-level megaraid 30: 10432 10722 IO-APIC-level aic7xxx 31: 23 22 IO-APIC-level aic7xxx NMI: 0 ERR: 0
XT-PIC — This is the old AT computer interrupts.
IO-APIC-edge — The voltage signal on this interrupt transitions from low to high, creating an edge, where the interrupt occurs and is only signaled once. This kind of interrupt, as well as the IO-APIC-level interrupt, are only seen on systems with processors from the 586 family and higher.
IO-APIC-level — Generates interrupts when its voltage signal is high until the signal is low again.
00000000-0009fbff : System RAM 0009fc00-0009ffff : reserved 000a0000-000bffff : Video RAM area 000c0000-000c7fff : Video ROM 000f0000-000fffff : System ROM 00100000-07ffffff : System RAM 00100000-00291ba8 : Kernel code 00291ba9-002e09cb : Kernel data e0000000-e3ffffff : VIA Technologies, Inc. VT82C597 [Apollo VP3] e4000000-e7ffffff : PCI Bus #01 e4000000-e4003fff : Matrox Graphics, Inc. MGA G200 AGP e5000000-e57fffff : Matrox Graphics, Inc. MGA G200 AGP e8000000-e8ffffff : PCI Bus #01 e8000000-e8ffffff : Matrox Graphics, Inc. MGA G200 AGP ea000000-ea00007f : Digital Equipment Corporation DECchip 21140 [FasterNet] ea000000-ea00007f : tulip ffff0000-ffffffff : reserved
/proc/ioports provides a list of currently registered port regions used for input or output communication with a device. This file can be quite long. The following is a partial listing:
0000-001f : dma1 0020-003f : pic1 0040-005f : timer 0060-006f : keyboard 0070-007f : rtc 0080-008f : dma page reg 00a0-00bf : pic2 00c0-00df : dma2 00f0-00ff : fpu 0170-0177 : ide1 01f0-01f7 : ide0 02f8-02ff : serial(auto) 0376-0376 : ide1 03c0-03df : vga+ 03f6-03f6 : ide0 03f8-03ff : serial(auto) 0cf8-0cff : PCI conf1 d000-dfff : PCI Bus #01 e000-e00f : VIA Technologies, Inc. Bus Master IDE e000-e007 : ide0 e008-e00f : ide1 e800-e87f : Digital Equipment Corporation DECchip 21140 [FasterNet] e800-e87f : tulip
/proc/ files, kcore displays a size. This value is given in bytes and is equal to the size of the physical memory (RAM) used plus 4 KB.
gdb, and is not human readable.
/proc/kcore virtual file. The contents of the file scramble text output on the terminal. If this file is accidentally viewed, press Ctrl+C to stop the process and then type reset to bring back the command line prompt.
/sbin/klogd or /bin/dmesg.
uptime and other commands. A sample /proc/loadavg file looks similar to the following:
0.20 0.18 0.12 1/80 11206
/proc/locks file for a lightly loaded system looks similar to the following:
1: POSIX ADVISORY WRITE 3568 fd:00:2531452 0 EOF 2: FLOCK ADVISORY WRITE 3517 fd:00:2531448 0 EOF 3: POSIX ADVISORY WRITE 3452 fd:00:2531442 0 EOF 4: POSIX ADVISORY WRITE 3443 fd:00:2531440 0 EOF 5: POSIX ADVISORY WRITE 3326 fd:00:2531430 0 EOF 6: POSIX ADVISORY WRITE 3175 fd:00:2531425 0 EOF 7: POSIX ADVISORY WRITE 3056 fd:00:2548663 0 EOF
FLOCK signifying the older-style UNIX file locks from a flock system call and POSIX representing the newer POSIX locks from the lockf system call.
ADVISORY or MANDATORY. ADVISORY means that the lock does not prevent other people from accessing the data; it only prevents other attempts to lock it. MANDATORY means that no other access to the data is permitted while the lock is held. The fourth column reveals whether the lock is allowing the holder READ or WRITE access to the file. The fifth column shows the ID of the process holding the lock. The sixth column shows the ID of the file being locked, in the format of MAJOR-DEVICE:MINOR-DEVICE:INODE-NUMBER/proc/mdstat looks similar to the following:
Personalities : read_ahead not set unused devices: <none>
md device is present. In that case, view /proc/mdstat to find the current status of mdX RAID devices.
/proc/mdstat file below shows a system with its md0 configured as a RAID 1 device, while it is currently re-syncing the disks:
Personalities : [linear] [raid1] read_ahead 1024 sectors md0: active raid1 sda2[1] sdb2[0] 9940 blocks [2/2] [UU] resync=1% finish=12.3min algorithm 2 [3/3] [UUU] unused devices: <none>
/proc/ directory, as it reports a large amount of valuable information about the systems RAM usage.
/proc/meminfo virtual file is from a system with 256 MB of RAM and 512 MB of swap space:
MemTotal: 255908 kB MemFree: 69936 kB Buffers: 15812 kB Cached: 115124 kB SwapCached: 0 kB Active: 92700 kB Inactive: 63792 kB HighTotal: 0 kB HighFree: 0 kB LowTotal: 255908 kB LowFree: 69936 kB SwapTotal: 524280 kB SwapFree: 524280 kB Dirty: 4 kB Writeback: 0 kB Mapped: 42236 kB Slab: 25912 kB Committed_AS: 118680 kB PageTables: 1236 kB VmallocTotal: 3874808 kB VmallocUsed: 1416 kB VmallocChunk: 3872908 kB HugePages_Total: 0 HugePages_Free: 0 Hugepagesize: 4096 kB
free, top, and ps commands. In fact, the output of the free command is similar in appearance to the contents and structure of /proc/meminfo. But by looking directly at /proc/meminfo, more details are revealed:
MemTotal — Total amount of physical RAM, in kilobytes.
MemFree — The amount of physical RAM, in kilobytes, left unused by the system.
Buffers — The amount of physical RAM, in kilobytes, used for file buffers.
Cached — The amount of physical RAM, in kilobytes, used as cache memory.
SwapCached — The amount of swap, in kilobytes, used as cache memory.
Active — The total amount of buffer or page cache memory, in kilobytes, that is in active use. This is memory that has been recently used and is usually not reclaimed for other purposes.
Inactive — The total amount of buffer or page cache memory, in kilobytes, that are free and available. This is memory that has not been recently used and can be reclaimed for other purposes.
HighTotal and HighFree — The total and free amount of memory, in kilobytes, that is not directly mapped into kernel space. The HighTotal value can vary based on the type of kernel used.
LowTotal and LowFree — The total and free amount of memory, in kilobytes, that is directly mapped into kernel space. The LowTotal value can vary based on the type of kernel used.
SwapTotal — The total amount of swap available, in kilobytes.
SwapFree — The total amount of swap free, in kilobytes.
Dirty — The total amount of memory, in kilobytes, waiting to be written back to the disk.
Writeback — The total amount of memory, in kilobytes, actively being written back to the disk.
Mapped — The total amount of memory, in kilobytes, which have been used to map devices, files, or libraries using the mmap command.
Slab — The total amount of memory, in kilobytes, used by the kernel to cache data structures for its own use.
Committed_AS — The total amount of memory, in kilobytes, estimated to complete the workload. This value represents the worst case scenario value, and also includes swap memory.
PageTables — The total amount of memory, in kilobytes, dedicated to the lowest page table level.
VMallocTotal — The total amount of memory, in kilobytes, of total allocated virtual address space.
VMallocUsed — The total amount of memory, in kilobytes, of used virtual address space.
VMallocChunk — The largest contiguous block of memory, in kilobytes, of available virtual address space.
HugePages_Total — The total number of hugepages for the system. The number is derived by dividing Hugepagesize by the megabytes set aside for hugepages specified in /proc/sys/vm/hugetlb_pool. This statistic only appears on the x86, Itanium, and AMD64 architectures.
HugePages_Free — The total number of hugepages available for the system. This statistic only appears on the x86, Itanium, and AMD64 architectures.
Hugepagesize — The size for each hugepages unit in kilobytes. By default, the value is 4096 KB on uniprocessor kernels for 32 bit architectures. For SMP, hugemem kernels, and AMD64, the default is 2048 KB. For Itanium architectures, the default is 262144 KB. This statistic only appears on the x86, Itanium, and AMD64 architectures.
63 device-mapper 175 agpgart 135 rtc 134 apm_bios
/proc/modules file output:
/sbin/lsmod command.
nfs 170109 0 - Live 0x129b0000 lockd 51593 1 nfs, Live 0x128b0000 nls_utf8 1729 0 - Live 0x12830000 vfat 12097 0 - Live 0x12823000 fat 38881 1 vfat, Live 0x1287b000 autofs4 20293 2 - Live 0x1284f000 sunrpc 140453 3 nfs,lockd, Live 0x12954000 3c59x 33257 0 - Live 0x12871000 uhci_hcd 28377 0 - Live 0x12869000 md5 3777 1 - Live 0x1282c000 ipv6 211845 16 - Live 0x128de000 ext3 92585 2 - Live 0x12886000 jbd 65625 1 ext3, Live 0x12857000 dm_mod 46677 3 - Live 0x12833000
Live, Loading, or Unloading are the only possible values.
oprofile.
rootfs / rootfs rw 0 0 /proc /proc proc rw,nodiratime 0 0 none /dev ramfs rw 0 0 /dev/mapper/VolGroup00-LogVol00 / ext3 rw 0 0 none /dev ramfs rw 0 0 /proc /proc proc rw,nodiratime 0 0 /sys /sys sysfs rw 0 0 none /dev/pts devpts rw 0 0 usbdevfs /proc/bus/usb usbdevfs rw 0 0 /dev/hda1 /boot ext3 rw 0 0 none /dev/shm tmpfs rw 0 0 none /proc/sys/fs/binfmt_misc binfmt_misc rw 0 0 sunrpc /var/lib/nfs/rpc_pipefs rpc_pipefs rw 0 0
/etc/mtab, except that /proc/mounts is more up-to-date.
ro) or read-write (rw). The fifth and sixth columns are dummy values designed to match the format used in /etc/mtab.
/proc/mtrr file may look similar to the following:
reg00: base=0x00000000 ( 0MB), size= 256MB: write-back, count=1 reg01: base=0xe8000000 (3712MB), size= 32MB: write-combining, count=1
/proc/mtrr file can increase performance more than 150%.
/usr/share/doc/kernel-doc-<kernel_version>/Documentation/<arch>/mtrr.txt
major minor #blocks name 3 0 19531250 hda 3 1 104391 hda1 3 2 19422585 hda2 253 0 22708224 dm-0 253 1 524288 dm-1
major — The major number of the device with this partition. The major number in the /proc/partitions, (3), corresponds with the block device ide0, in /proc/devices.
minor — The minor number of the device with this partition. This serves to separate the partitions into different physical devices and relates to the number at the end of the name of the partition.
#blocks — Lists the number of physical disk blocks contained in a particular partition.
name — The name of the partition.
/proc/slabinfo file manually, the /usr/bin/slabtop program displays kernel slab cache information in real time. This program allows for custom configurations, including column sorting and screen refreshing.
/usr/bin/slabtop usually looks like the following example:
Active / Total Objects (% used) : 133629 / 147300 (90.7%) Active / Total Slabs (% used) : 11492 / 11493 (100.0%) Active / Total Caches (% used) : 77 / 121 (63.6%) Active / Total Size (% used) : 41739.83K / 44081.89K (94.7%) Minimum / Average / Maximum Object : 0.01K / 0.30K / 128.00K OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME 44814 43159 96% 0.62K 7469 6 29876K ext3_inode_cache 36900 34614 93% 0.05K 492 75 1968K buffer_head 35213 33124 94% 0.16K 1531 23 6124K dentry_cache 7364 6463 87% 0.27K 526 14 2104K radix_tree_node 2585 1781 68% 0.08K 55 47 220K vm_area_struct 2263 2116 93% 0.12K 73 31 292K size-128 1904 1125 59% 0.03K 16 119 64K size-32 1666 768 46% 0.03K 14 119 56K anon_vma 1512 1482 98% 0.44K 168 9 672K inode_cache 1464 1040 71% 0.06K 24 61 96K size-64 1320 820 62% 0.19K 66 20 264K filp 678 587 86% 0.02K 3 226 12K dm_io 678 587 86% 0.02K 3 226 12K dm_tio 576 574 99% 0.47K 72 8 288K proc_inode_cache 528 514 97% 0.50K 66 8 264K size-512 492 372 75% 0.09K 12 41 48K bio 465 314 67% 0.25K 31 15 124K size-256 452 331 73% 0.02K 2 226 8K biovec-1 420 420 100% 0.19K 21 20 84K skbuff_head_cache 305 256 83% 0.06K 5 61 20K biovec-4 290 4 1% 0.01K 1 290 4K revoke_table 264 264 100% 4.00K 264 1 1056K size-4096 260 256 98% 0.19K 13 20 52K biovec-16 260 256 98% 0.75K 52 5 208K biovec-64
/proc/slabinfo that are included into /usr/bin/slabtop include:
OBJS — The total number of objects (memory blocks), including those in use (allocated), and some spares not in use.
ACTIVE — The number of objects (memory blocks) that are in use (allocated).
USE — Percentage of total objects that are active. ((ACTIVE/OBJS)(100))
OBJ SIZE — The size of the objects.
SLABS — The total number of slabs.
OBJ/SLAB — The number of objects that fit into a slab.
CACHE SIZE — The cache size of the slab.
NAME — The name of the slab.
/usr/bin/slabtop program, refer to the slabtop man page.
/proc/stat, which can be quite long, usually begins like the following example:
cpu 259246 7001 60190 34250993 137517 772 0 cpu0 259246 7001 60190 34250993 137517 772 0 intr 354133732 347209999 2272 0 4 4 0 0 3 1 1249247 0 0 80143 0 422626 5169433 ctxt 12547729 btime 1093631447 processes 130523 procs_running 1 procs_blocked 0 preempt 5651840 cpu 209841 1554 21720 118519346 72939 154 27168 cpu0 42536 798 4841 14790880 14778 124 3117 cpu1 24184 569 3875 14794524 30209 29 3130 cpu2 28616 11 2182 14818198 4020 1 3493 cpu3 35350 6 2942 14811519 3045 0 3659 cpu4 18209 135 2263 14820076 12465 0 3373 cpu5 20795 35 1866 14825701 4508 0 3615 cpu6 21607 0 2201 14827053 2325 0 3334 cpu7 18544 0 1550 14831395 1589 0 3447 intr 15239682 14857833 6 0 6 6 0 5 0 1 0 0 0 29 0 2 0 0 0 0 0 0 0 94982 0 286812 ctxt 4209609 btime 1078711415 processes 21905 procs_running 1 procs_blocked 0
cpu — Measures the number of jiffies (1/100 of a second for x86 systems) that the system has been in user mode, user mode with low priority (nice), system mode, idle task, I/O wait, IRQ (hardirq), and softirq respectively. The IRQ (hardirq) is the direct response to a hardware event. The IRQ takes minimal work for queuing the "heavy" work up for the softirq to execute. The softirq runs at a lower priority than the IRQ and therefore may be interrupted more frequently. The total for all CPUs is given at the top, while each individual CPU is listed below with its own statistics. The following example is a 4-way Intel Pentium Xeon configuration with multi-threading enabled, therefore showing four physical processors and four virtual processors totaling eight processors.
page — The number of memory pages the system has written in and out to disk.
swap — The number of swap pages the system has brought in and out.
intr — The number of interrupts the system has experienced.
btime — The boot time, measured in the number of seconds since January 1, 1970, otherwise known as the epoch.
/proc/swaps may look similar to the following:
Filename Type Size Used Priority /dev/mapper/VolGroup00-LogVol01 partition 524280 0 -1
/proc/ directory, /proc/swap provides a snapshot of every swap file name, the type of swap space, the total size, and the amount of space in use (in kilobytes). The priority column is useful when multiple swap files are in use. The lower the priority, the more likely the swap file is to be used.
echo command to write to this file, a remote root user can execute most System Request Key commands remotely as if at the local terminal. To echo values to this file, the /proc/sys/kernel/sysrq must be set to a value other than 0. For more information about the System Request Key, refer to Section E.3.9.3, “/proc/sys/kernel/”.
/proc/uptime is quite minimal:
350735.47 234388.90
gcc used to compile the kernel, and the time of kernel compilation. It also contains the kernel compiler's user name (in parentheses).
Linux version 2.6.8-1.523 (user@foo.redhat.com) (gcc version 3.4.1 20040714 \ (Red Hat Enterprise Linux 3.4.1-7)) #1 Mon Aug 16 13:27:03 EDT 2004
/proc/ directory.
/proc/ directory contains a number of directories with numerical names. A listing of them may be similar to the following:
dr-xr-xr-x 3 root root 0 Feb 13 01:28 1 dr-xr-xr-x 3 root root 0 Feb 13 01:28 1010 dr-xr-xr-x 3 xfs xfs 0 Feb 13 01:28 1087 dr-xr-xr-x 3 daemon daemon 0 Feb 13 01:28 1123 dr-xr-xr-x 3 root root 0 Feb 13 01:28 11307 dr-xr-xr-x 3 apache apache 0 Feb 13 01:28 13660 dr-xr-xr-x 3 rpc rpc 0 Feb 13 01:28 637 dr-xr-xr-x 3 rpcuser rpcuser 0 Feb 13 01:28 666
/proc/ process directory vanishes.
cmdline — Contains the command issued when starting the process.
cwd — A symbolic link to the current working directory for the process.
environ — A list of the environment variables for the process. The environment variable is given in all upper-case characters, and the value is in lower-case characters.
exe — A symbolic link to the executable of this process.
fd — A directory containing all of the file descriptors for a particular process. These are given in numbered links:
total 0 lrwx------ 1 root root 64 May 8 11:31 0 -> /dev/null lrwx------ 1 root root 64 May 8 11:31 1 -> /dev/null lrwx------ 1 root root 64 May 8 11:31 2 -> /dev/null lrwx------ 1 root root 64 May 8 11:31 3 -> /dev/ptmx lrwx------ 1 root root 64 May 8 11:31 4 -> socket:[7774817] lrwx------ 1 root root 64 May 8 11:31 5 -> /dev/ptmx lrwx------ 1 root root 64 May 8 11:31 6 -> socket:[7774829] lrwx------ 1 root root 64 May 8 11:31 7 -> /dev/ptmx
maps — A list of memory maps to the various executables and library files associated with this process. This file can be rather long, depending upon the complexity of the process, but sample output from the sshd process begins like the following:
08048000-08086000 r-xp 00000000 03:03 391479 /usr/sbin/sshd 08086000-08088000 rw-p 0003e000 03:03 391479 /usr/sbin/sshd 08088000-08095000 rwxp 00000000 00:00 0 40000000-40013000 r-xp 0000000 03:03 293205 /lib/ld-2.2.5.so 40013000-40014000 rw-p 00013000 03:03 293205 /lib/ld-2.2.5.so 40031000-40038000 r-xp 00000000 03:03 293282 /lib/libpam.so.0.75 40038000-40039000 rw-p 00006000 03:03 293282 /lib/libpam.so.0.75 40039000-4003a000 rw-p 00000000 00:00 0 4003a000-4003c000 r-xp 00000000 03:03 293218 /lib/libdl-2.2.5.so 4003c000-4003d000 rw-p 00001000 03:03 293218 /lib/libdl-2.2.5.so
mem — The memory held by the process. This file cannot be read by the user.
root — A link to the root directory of the process.
stat — The status of the process.
statm — The status of the memory in use by the process. Below is a sample /proc/statm file:
263 210 210 5 0 205 0
status — The status of the process in a more readable form than stat or statm. Sample output for sshd looks similar to the following:
Name: sshd State: S (sleeping) Tgid: 797 Pid: 797 PPid: 1 TracerPid: 0 Uid: 0 0 0 0 Gid: 0 0 0 0 FDSize: 32 Groups: VmSize: 3072 kB VmLck: 0 kB VmRSS: 840 kB VmData: 104 kB VmStk: 12 kB VmExe: 300 kB VmLib: 2528 kB SigPnd: 0000000000000000 SigBlk: 0000000000000000 SigIgn: 8000000000001000 SigCgt: 0000000000014005 CapInh: 0000000000000000 CapPrm: 00000000fffffeff CapEff: 00000000fffffeff
S (sleeping) or R (running)), user/group ID running the process, and detailed data regarding memory usage.
/proc/self/ directory is a link to the currently running process. This allows a process to look at itself without having to know its process ID.
/proc/self/ directory produces the same contents as listing the process directory for that process.
/proc/bus/ by the same name, such as /proc/bus/pci/.
/proc/bus/ vary depending on the devices connected to the system. However, each bus type has at least one directory. Within these bus directories are normally at least one subdirectory with a numerical name, such as 001, which contain binary files.
/proc/bus/usb/ subdirectory contains files that track the various devices on any USB buses, as well as the drivers required for them. The following is a sample listing of a /proc/bus/usb/ directory:
total 0 dr-xr-xr-x 1 root root 0 May 3 16:25 001 -r--r--r-- 1 root root 0 May 3 16:25 devices -r--r--r-- 1 root root 0 May 3 16:25 drivers
/proc/bus/usb/001/ directory contains all devices on the first USB bus and the devices file identifies the USB root hub on the motherboard.
/proc/bus/usb/devices file:
T: Bus=01 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#= 1 Spd=12 MxCh= 2 B: Alloc= 0/900 us ( 0%), #Int= 0, #Iso= 0 D: Ver= 1.00 Cls=09(hub ) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1 P: Vendor=0000 ProdID=0000 Rev= 0.00 S: Product=USB UHCI Root Hub S: SerialNumber=d400 C:* #Ifs= 1 Cfg#= 1 Atr=40 MxPwr= 0mA I: If#= 0 Alt= 0 #EPs= 1 Cls=09(hub ) Sub=00 Prot=00 Driver=hub E: Ad=81(I) Atr=03(Int.) MxPS= 8 Ivl=255ms
/proc/pci directory in favor of the /proc/bus/pci directory. Although you can get a list of all PCI devices present on the system using the command cat /proc/bus/pci/devices, the output is difficult to read and interpret.
~]# /sbin/lspci -vb
00:00.0 Host bridge: Intel Corporation 82X38/X48 Express DRAM Controller
Subsystem: Hewlett-Packard Company Device 1308
Flags: bus master, fast devsel, latency 0
Capabilities: [e0] Vendor Specific Information <?>
Kernel driver in use: x38_edac
Kernel modules: x38_edac
00:01.0 PCI bridge: Intel Corporation 82X38/X48 Express Host-Primary PCI Express Bridge (prog-if 00 [Normal decode])
Flags: bus master, fast devsel, latency 0
Bus: primary=00, secondary=01, subordinate=01, sec-latency=0
I/O behind bridge: 00001000-00001fff
Memory behind bridge: f0000000-f2ffffff
Capabilities: [88] Subsystem: Hewlett-Packard Company Device 1308
Capabilities: [80] Power Management version 3
Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit-
Capabilities: [a0] Express Root Port (Slot+), MSI 00
Capabilities: [100] Virtual Channel <?>
Capabilities: [140] Root Complex Link <?>
Kernel driver in use: pcieport
Kernel modules: shpchp
00:1a.0 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #4 (rev 02) (prog-if 00 [UHCI])
Subsystem: Hewlett-Packard Company Device 1308
Flags: bus master, medium devsel, latency 0, IRQ 5
I/O ports at 2100
Capabilities: [50] PCI Advanced Features
Kernel driver in use: uhci_hcd
[output truncated]rtc which provides output from the driver for the system's Real Time Clock (RTC), the device that keeps the time while the system is switched off. Sample output from /proc/driver/rtc looks like the following:
rtc_time : 16:21:00 rtc_date : 2004-08-31 rtc_epoch : 1900 alarm : 21:16:27 DST_enable : no BCD : yes 24hr : yes square_wave : no alarm_IRQ : no update_IRQ : no periodic_IRQ : no periodic_freq : 1024 batt_status : okay
/usr/share/doc/kernel-doc-<kernel_version>/Documentation/rtc.txt.
cat /proc/fs/nfsd/exports displays the file systems being shared and the permissions granted for those file systems. For more on file system sharing with NFS, refer to the Network File System (NFS) chapter of the Storage Administration Guide.
/proc/irq/prof_cpu_mask file is a bitmask that contains the default values for the smp_affinity file in the IRQ directory. The values in smp_affinity specify which CPUs handle that particular IRQ.
/proc/irq/ directory, refer to the following installed documentation:
/usr/share/doc/kernel-doc-kernel_version/Documentation/filesystems/proc.txt
/proc/net/ directory:
arp — Lists the kernel's ARP table. This file is particularly useful for connecting a hardware address to an IP address on a system.
atm/ directory — The files within this directory contain Asynchronous Transfer Mode (ATM) settings and statistics. This directory is primarily used with ATM networking and ADSL cards.
dev — Lists the various network devices configured on the system, complete with transmit and receive statistics. This file displays the number of bytes each interface has sent and received, the number of packets inbound and outbound, the number of errors seen, the number of packets dropped, and more.
dev_mcast — Lists Layer2 multicast groups on which each device is listening.
igmp — Lists the IP multicast addresses which this system joined.
ip_conntrack — Lists tracked network connections for machines that are forwarding IP connections.
ip_tables_names — Lists the types of iptables in use. This file is only present if iptables is active on the system and contains one or more of the following values: filter, mangle, or nat.
ip_mr_cache — Lists the multicast routing cache.
ip_mr_vif — Lists multicast virtual interfaces.
netstat — Contains a broad yet detailed collection of networking statistics, including TCP timeouts, SYN cookies sent and received, and much more.
psched — Lists global packet scheduler parameters.
raw — Lists raw device statistics.
route — Lists the kernel's routing table.
rt_cache — Contains the current routing cache.
snmp — List of Simple Network Management Protocol (SNMP) data for various networking protocols in use.
sockstat — Provides socket statistics.
tcp — Contains detailed TCP socket information.
tr_rif — Lists the token ring RIF routing table.
udp — Contains detailed UDP socket information.
unix — Lists UNIX domain sockets currently in use.
wireless — Lists wireless interface data.
/proc/scsi/scsi, which contains a list of every recognized SCSI device. From this listing, the type of device, as well as the model name, vendor, SCSI channel and ID data is available.
Attached devices: Host: scsi1 Channel: 00 Id: 05 Lun: 00 Vendor: NEC Model: CD-ROM DRIVE:466 Rev: 1.06 Type: CD-ROM ANSI SCSI revision: 02 Host: scsi1 Channel: 00 Id: 06 Lun: 00 Vendor: ARCHIVE Model: Python 04106-XXX Rev: 7350 Type: Sequential-Access ANSI SCSI revision: 02 Host: scsi2 Channel: 00 Id: 06 Lun: 00 Vendor: DELL Model: 1x6 U2W SCSI BP Rev: 5.35 Type: Processor ANSI SCSI revision: 02 Host: scsi2 Channel: 02 Id: 00 Lun: 00 Vendor: MegaRAID Model: LD0 RAID5 34556R Rev: 1.01 Type: Direct-Access ANSI SCSI revision: 02
/proc/scsi/, which contains files specific to each SCSI controller using that driver. From the previous example, aic7xxx/ and megaraid/ directories are present, since two drivers are in use. The files in each of the directories typically contain an I/O address range, IRQ information, and statistics for the SCSI controller using that driver. Each controller can report a different type and amount of information. The Adaptec AIC-7880 Ultra SCSI host adapter's file in this example system produces the following output:
Adaptec AIC7xxx driver version: 5.1.20/3.2.4
Compile Options:
TCQ Enabled By Default : Disabled
AIC7XXX_PROC_STATS : Enabled
AIC7XXX_RESET_DELAY : 5
Adapter Configuration:
SCSI Adapter: Adaptec AIC-7880 Ultra SCSI host adapter
Ultra Narrow Controller PCI MMAPed
I/O Base: 0xfcffe000
Adapter SEEPROM Config: SEEPROM found and used.
Adaptec SCSI BIOS: Enabled
IRQ: 30
SCBs: Active 0, Max Active 1, Allocated 15, HW 16, Page 255
Interrupts: 33726
BIOS Control Word: 0x18a6
Adapter Control Word: 0x1c5f
Extended Translation: Enabled
Disconnect Enable Flags: 0x00ff
Ultra Enable Flags: 0x0020
Tag Queue Enable Flags: 0x0000
Ordered Queue Tag Flags: 0x0000
Default Tag Queue Depth: 8
Tagged Queue By Device array for aic7xxx
host instance 1: {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
Actual queue depth per device for aic7xxx host instance 1: {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
Statistics:
(scsi1:0:5:0) Device using Narrow/Sync transfers at 20.0 MByte/sec, offset 15
Transinfo settings: current(12/15/0/0), goal(12/15/0/0), user(12/15/0/0)
Total transfers 0 (0 reads and 0 writes)
< 2K 2K+ 4K+ 8K+ 16K+ 32K+ 64K+ 128K+
Reads: 0 0 0 0 0 0 0 0
Writes: 0 0 0 0 0 0 0 0
(scsi1:0:6:0) Device using Narrow/Sync transfers at 10.0 MByte/sec, offset 15
Transinfo settings: current(25/15/0/0), goal(12/15/0/0), user(12/15/0/0)
Total transfers 132 (0 reads and 132 writes)
< 2K 2K+ 4K+ 8K+ 16K+ 32K+ 64K+ 128K+
Reads: 0 0 0 0 0 0 0 0
Writes: 0 0 0 1 131 0 0 0
/proc/sys/ directory is different from others in /proc/ because it not only provides information about the system but also allows the system administrator to immediately enable and disable kernel features.
/proc/sys/ directory. Changing the wrong setting may render the kernel unstable, requiring a system reboot.
/proc/sys/.
-l option at the shell prompt. If the file is writable, it may be used to configure the kernel. For example, a partial listing of /proc/sys/fs looks like the following:
-r--r--r-- 1 root root 0 May 10 16:14 dentry-state -rw-r--r-- 1 root root 0 May 10 16:14 dir-notify-enable -rw-r--r-- 1 root root 0 May 10 16:14 file-max -r--r--r-- 1 root root 0 May 10 16:14 file-nr
dir-notify-enable and file-max can be written to and, therefore, can be used to configure the kernel. The other files only provide feedback on current settings.
/proc/sys/ file is done by echoing the new value into the file. For example, to enable the System Request Key on a running kernel, type the command:
echo 1 > /proc/sys/kernel/sysrq
sysrq from 0 (off) to 1 (on).
/proc/sys/ configuration files contain more than one value. To correctly send new values to them, place a space character between each value passed with the echo command, such as is done in this example:
echo 4 2 45 > /proc/sys/kernel/acct
echo command disappear when the system is restarted. To make configuration changes take effect after the system is rebooted, refer to Section E.4, “Using the sysctl Command”.
/proc/sys/ directory contains several subdirectories controlling different aspects of a running kernel.
cdrom/ and raid/. Customized kernels can have other directories, such as parport/, which provides the ability to share one parallel port between multiple device drivers.
cdrom/ directory contains a file called info, which reveals a number of important CD-ROM parameters:
CD-ROM information, Id: cdrom.c 3.20 2003/12/17 drive name: hdc drive speed: 48 drive # of slots: 1 Can close tray: 1 Can open tray: 1 Can lock tray: 1 Can change speed: 1 Can select disk: 0 Can read multisession: 1 Can read MCN: 1 Reports media changed: 1 Can play audio: 1 Can write CD-R: 0 Can write CD-RW: 0 Can read DVD: 0 Can write DVD-R: 0 Can write DVD-RAM: 0 Can read MRW: 0 Can write MRW: 0 Can write RAM: 0
/proc/sys/dev/cdrom, such as autoclose and checkmedia, can be used to control the system's CD-ROM. Use the echo command to enable or disable these features.
/proc/sys/dev/raid/ directory becomes available with at least two files in it: speed_limit_min and speed_limit_max. These settings determine the acceleration of RAID devices for I/O intensive tasks, such as resyncing the disks.
binfmt_misc/ directory is used to provide kernel support for miscellaneous binary formats.
/proc/sys/fs/ include:
dentry-state — Provides the status of the directory cache. The file looks similar to the following:
57411 52939 45 0 0 0
file-max — Lists the maximum number of file handles that the kernel allocates. Raising the value in this file can resolve errors caused by a lack of available file handles.
file-nr — Lists the number of allocated file handles, used file handles, and the maximum number of file handles.
overflowgid and overflowuid — Defines the fixed group ID and user ID, respectively, for use with file systems that only support 16-bit group and user IDs.
acct — Controls the suspension of process accounting based on the percentage of free space available on the file system containing the log. By default, the file looks like the following:
4 2 30
ctrl-alt-del — Controls whether Ctrl+Alt+Delete gracefully restarts the computer using init (0) or forces an immediate reboot without syncing the dirty buffers to disk (1).
domainname — Configures the system domain name, such as example.com.
exec-shield — Configures the Exec Shield feature of the kernel. Exec Shield provides protection against certain types of buffer overflow attacks.
0 — Disables Exec Shield.
1 — Enables Exec Shield. This is the default value.
hostname — Configures the system hostname, such as www.example.com.
hotplug — Configures the utility to be used when a configuration change is detected by the system. This is primarily used with USB and Cardbus PCI. The default value of /sbin/hotplug should not be changed unless testing a new program to fulfill this role.
modprobe — Sets the location of the program used to load kernel modules. The default value is /sbin/modprobe which means kmod calls it to load the module when a kernel thread calls kmod.
msgmax — Sets the maximum size of any message sent from one process to another and is set to 8192 bytes by default. Be careful when raising this value, as queued messages between processes are stored in non-swappable kernel memory. Any increase in msgmax would increase RAM requirements for the system.
msgmnb — Sets the maximum number of bytes in a single message queue. The default is 16384.
msgmni — Sets the maximum number of message queue identifiers. The default is 4008.
osrelease — Lists the Linux kernel release number. This file can only be altered by changing the kernel source and recompiling.
ostype — Displays the type of operating system. By default, this file is set to Linux, and this value can only be changed by changing the kernel source and recompiling.
overflowgid and overflowuid — Defines the fixed group ID and user ID, respectively, for use with system calls on architectures that only support 16-bit group and user IDs.
panic — Defines the number of seconds the kernel postpones rebooting when the system experiences a kernel panic. By default, the value is set to 0, which disables automatic rebooting after a panic.
printk — This file controls a variety of settings related to printing or logging error messages. Each error message reported by the kernel has a loglevel associated with it that defines the importance of the message. The loglevel values break down in this order:
0 — Kernel emergency. The system is unusable.
1 — Kernel alert. Action must be taken immediately.
2 — Condition of the kernel is considered critical.
3 — General kernel error condition.
4 — General kernel warning condition.
5 — Kernel notice of a normal but significant condition.
6 — Kernel informational message.
7 — Kernel debug-level messages.
printk file:
6 4 1 7
random/ directory — Lists a number of values related to generating random numbers for the kernel.
sem — Configures semaphore settings within the kernel. A semaphore is a System V IPC object that is used to control utilization of a particular process.
shmall — Sets the total amount of shared memory that can be used at one time on the system, in bytes. By default, this value is 2097152.
shmmax — Sets the largest shared memory segment size allowed by the kernel. By default, this value is 33554432. However, the kernel supports much larger values than this.
shmmni — Sets the maximum number of shared memory segments for the whole system. By default, this value is 4096.
sysrq — Activates the System Request Key, if this value is set to anything other than zero (0), the default.
system request code. Replace system request code with one of the following system request codes:
r — Disables raw mode for the keyboard and sets it to XLATE (a limited keyboard mode which does not recognize modifiers such as Alt, Ctrl, or Shift for all keys).
k — Kills all processes active in a virtual console. Also called Secure Access Key (SAK), it is often used to verify that the login prompt is spawned from init and not a trojan copy designed to capture usernames and passwords.
b — Reboots the kernel without first unmounting file systems or syncing disks attached to the system.
c — Crashes the system without first unmounting file systems or syncing disks attached to the system.
o — Shuts off the system.
s — Attempts to sync disks attached to the system.
u — Attempts to unmount and remount all file systems as read-only.
p — Outputs all flags and registers to the console.
t — Outputs a list of processes to the console.
m — Outputs memory statistics to the console.
0 through 9 — Sets the log level for the console.
e — Kills all processes except init using SIGTERM.
i — Kills all processes except init using SIGKILL.
l — Kills all processes using SIGKILL (including init). The system is unusable after issuing this System Request Key code.
h — Displays help text.
/usr/share/doc/kernel-doc-kernel_version/Documentation/sysrq.txt for more information about the System Request Key.
tainted — Indicates whether a non-GPL module is loaded.
0 — No non-GPL modules are loaded.
1 — At least one module without a GPL license (including modules with no license) is loaded.
2 — At least one module was force-loaded with the command insmod -f.
threads-max — Sets the maximum number of threads to be used by the kernel, with a default value of 2048.
version — Displays the date and time the kernel was last compiled. The first field in this file, such as #3, relates to the number of times a kernel was built from the source base.
ethernet/, ipv4/, ipx/, and ipv6/. By altering the files within these directories, system administrators are able to adjust the network configuration on a running system.
/proc/sys/net/ directories are discussed.
/proc/sys/net/core/ directory contains a variety of settings that control the interaction between the kernel and networking layers. The most important of these files are:
message_burst — Sets the amount of time in tenths of a second required to write a new warning message. This setting is used to mitigate Denial of Service (DoS) attacks. The default setting is 10.
message_cost — Sets a cost on every warning message. The higher the value of this file (default of 5), the more likely the warning message is ignored. This setting is used to mitigate DoS attacks.
message_burst and message_cost are designed to be modified based on the system's acceptable risk versus the need for comprehensive logging.
netdev_max_backlog — Sets the maximum number of packets allowed to queue when a particular interface receives packets faster than the kernel can process them. The default value for this file is 1000.
optmem_max — Configures the maximum ancillary buffer size allowed per socket.
rmem_default — Sets the receive socket buffer default size in bytes.
rmem_max — Sets the receive socket buffer maximum size in bytes.
wmem_default — Sets the send socket buffer default size in bytes.
wmem_max — Sets the send socket buffer maximum size in bytes.
/proc/sys/net/ipv4/ directory contains additional networking settings. Many of these settings, used in conjunction with one another, are useful in preventing attacks on the system or when using the system to act as a router.
/proc/sys/net/ipv4/ directory:
icmp_echo_ignore_all and icmp_echo_ignore_broadcasts — Allows the kernel to ignore ICMP ECHO packets from every host or only those originating from broadcast and multicast addresses, respectively. A value of 0 allows the kernel to respond, while a value of 1 ignores the packets.
ip_default_ttl — Sets the default Time To Live (TTL), which limits the number of hops a packet may make before reaching its destination. Increasing this value can diminish system performance.
ip_forward — Permits interfaces on the system to forward packets to one other. By default, this file is set to 0. Setting this file to 1 enables network packet forwarding.
ip_local_port_range — Specifies the range of ports to be used by TCP or UDP when a local port is needed. The first number is the lowest port to be used and the second number specifies the highest port. Any systems that expect to require more ports than the default 1024 to 4999 should use a range from 32768 to 61000.
tcp_syn_retries — Provides a limit on the number of times the system re-transmits a SYN packet when attempting to make a connection.
tcp_retries1 — Sets the number of permitted re-transmissions attempting to answer an incoming connection. Default of 3.
tcp_retries2 — Sets the number of permitted re-transmissions of TCP packets. Default of 15.
/usr/share/doc/kernel-doc-kernel_version/Documentation/networking/ip-sysctl.txt/proc/sys/net/ipv4/ directory.
/proc/sys/net/ipv4/ directory and each covers a different aspect of the network stack. The /proc/sys/net/ipv4/conf/ directory allows each system interface to be configured in different ways, including the use of default settings for unconfigured devices (in the /proc/sys/net/ipv4/conf/default/ subdirectory) and settings that override all special configurations (in the /proc/sys/net/ipv4/conf/all/ subdirectory).
/proc/sys/net/ipv4/neigh/ directory contains settings for communicating with a host directly connected to the system (called a network neighbor) and also contains different settings for systems more than one hop away.
/proc/sys/net/ipv4/route/. Unlike conf/ and neigh/, the /proc/sys/net/ipv4/route/ directory contains specifications that apply to routing with any interfaces on the system. Many of these settings, such as max_size, max_delay, and min_delay, relate to controlling the size of the routing cache. To clear the routing cache, write any value to the flush file.
/usr/share/doc/kernel-doc-kernel_version/Documentation/filesystems/proc.txt
/proc/sys/vm/ directory:
block_dump — Configures block I/O debugging when enabled. All read/write and block dirtying operations done to files are logged accordingly. This can be useful if diagnosing disk spin up and spin downs for laptop battery conservation. All output when block_dump is enabled can be retrieved via dmesg. The default value is 0.
block_dump is enabled at the same time as kernel debugging, it is prudent to stop the klogd daemon, as it generates erroneous disk activity caused by block_dump.
dirty_background_ratio — Starts background writeback of dirty data at this percentage of total memory, via a pdflush daemon. The default value is 10.
dirty_expire_centisecs — Defines when dirty in-memory data is old enough to be eligible for writeout. Data which has been dirty in-memory for longer than this interval is written out next time a pdflush daemon wakes up. The default value is 3000, expressed in hundredths of a second.
dirty_ratio — Starts active writeback of dirty data at this percentage of total memory for the generator of dirty data, via pdflush. The default value is 20.
dirty_writeback_centisecs — Defines the interval between pdflush daemon wakeups, which periodically writes dirty in-memory data out to disk. The default value is 500, expressed in hundredths of a second.
laptop_mode — Minimizes the number of times that a hard disk needs to spin up by keeping the disk spun down for as long as possible, therefore conserving battery power on laptops. This increases efficiency by combining all future I/O processes together, reducing the frequency of spin ups. The default value is 0, but is automatically enabled in case a battery on a laptop is used.
/usr/share/doc/kernel-doc-kernel_version/Documentation/laptop-mode.txt
max_map_count — Configures the maximum number of memory map areas a process may have. In most cases, the default value of 65536 is appropriate.
min_free_kbytes — Forces the Linux VM (virtual memory manager) to keep a minimum number of kilobytes free. The VM uses this number to compute a pages_min value for each lowmem zone in the system. The default value is in respect to the total memory on the machine.
nr_hugepages — Indicates the current number of configured hugetlb pages in the kernel.
/usr/share/doc/kernel-doc-kernel_version/Documentation/vm/hugetlbpage.txt
nr_pdflush_threads — Indicates the number of pdflush daemons that are currently running. This file is read-only, and should not be changed by the user. Under heavy I/O loads, the default value of two is increased by the kernel.
overcommit_memory — Configures the conditions under which a large memory request is accepted or denied. The following three modes are available:
0 — The kernel performs heuristic memory over commit handling by estimating the amount of memory available and failing requests that are blatantly invalid. Unfortunately, since memory is allocated using a heuristic rather than a precise algorithm, this setting can sometimes allow available memory on the system to be overloaded. This is the default setting.
1 — The kernel performs no memory over commit handling. Under this setting, the potential for memory overload is increased, but so is performance for memory intensive tasks (such as those executed by some scientific software).
2 — The kernel fails requests for memory that add up to all of swap plus the percent of physical RAM specified in /proc/sys/vm/overcommit_ratio. This setting is best for those who desire less risk of memory overcommitment.
overcommit_ratio — Specifies the percentage of physical RAM considered when /proc/sys/vm/overcommit_memory is set to 2. The default value is 50.
page-cluster — Sets the number of pages read in a single attempt. The default value of 3, which actually relates to 16 pages, is appropriate for most systems.
swappiness — Determines how much a machine should swap. The higher the value, the more swapping occurs. The default value, as a percentage, is set to 60.
/usr/share/doc/kernel-doc-kernel_version/Documentation/, which contains additional information.
msg), semaphores (sem), and shared memory (shm).
drivers file is a list of the current tty devices in use, as in the following example:
serial /dev/cua 5 64-127 serial:callout serial /dev/ttyS 4 64-127 serial pty_slave /dev/pts 136 0-255 pty:slave pty_master /dev/ptm 128 0-255 pty:master pty_slave /dev/ttyp 3 0-255 pty:slave pty_master /dev/pty 2 0-255 pty:master /dev/vc/0 /dev/vc/0 4 0 system:vtmaster /dev/ptmx /dev/ptmx 5 2 system /dev/console /dev/console 5 1 system:console /dev/tty /dev/tty 5 0 system:/dev/tty unknown /dev/vc/%d 4 1-63 console
/proc/tty/driver/serial file lists the usage statistics and status of each of the serial tty lines.
PID//proc/sys/vm/panic_on_oom. When set to 1 the kernel will panic on OOM. A setting of 0 instructs the kernel to call a function named oom_killer on an OOM. Usually, oom_killer can kill rogue processes and the system will survive.
/proc/sys/vm/panic_on_oom.
# cat /proc/sys/vm/panic_on_oom 1 # echo 0 > /proc/sys/vm/panic_on_oom # cat /proc/sys/vm/panic_on_oom 0
oom_killer score. In /proc/PID/ there are two tools labeled oom_adj and oom_score. Valid scores for oom_adj are in the range -16 to +15. To see the current oom_killer score, view the oom_score for the process. oom_killer will kill processes with the highest scores first.
PID of 12465 to make it less likely that oom_killer will kill it.
# cat /proc/12465/oom_score 79872 # echo -5 > /proc/12465/oom_adj # cat /proc/12465/oom_score 78
oom_killer for that process. In the example below, oom_score returns a value of 0, indicating that this process would not be killed.
# cat /proc/12465/oom_score 78 # echo -17 > /proc/12465/oom_adj # cat /proc/12465/oom_score 0
badness() is used to determine the actual score for each process. This is done by adding up 'points' for each examined process. The process scoring is done in the following way:
CAP_SYS_ADMIN and CAP_SYS_RAWIO capabilities have their scores reduced.
oom_adj file.
oom_score value will most probably be a non-priviliged, recently started process that, along with its children, uses a large amount of memory, has been 'niced', and handles no raw I/O.
/sbin/sysctl command is used to view, set, and automate kernel settings in the /proc/sys/ directory.
/proc/sys/ directory, type the /sbin/sysctl -a command as root. This creates a large, comprehensive list, a small portion of which looks something like the following:
net.ipv4.route.min_delay = 2 kernel.sysrq = 0 kernel.sem = 250 32000 32 128
/proc/sys/net/ipv4/route/min_delay file is listed as net.ipv4.route.min_delay, with the directory slashes replaced by dots and the proc.sys portion assumed.
sysctl command can be used in place of echo to assign values to writable files in the /proc/sys/ directory. For example, instead of using the command
echo 1 > /proc/sys/kernel/sysrq
sysctl command as follows:
sysctl -w kernel.sysrq="1" kernel.sysrq = 1
/proc/sys/ is helpful during testing, this method does not work as well on a production system as special settings within /proc/sys/ are lost when the machine is rebooted. To preserve custom settings, add them to the /etc/sysctl.conf file.
init program runs the /etc/rc.d/rc.sysinit script. This script contains a command to execute sysctl using /etc/sysctl.conf to determine the values passed to the kernel. Any values added to /etc/sysctl.conf therefore take effect each time the system boots.
proc file system.
proc file system is installed on the system by default.
/usr/share/doc/kernel-doc-kernel_version/Documentation/filesystems/proc.txt — Contains assorted, but limited, information about all aspects of the /proc/ directory.
/usr/share/doc/kernel-doc-kernel_version/Documentation/sysrq.txt — An overview of System Request Key options.
/usr/share/doc/kernel-doc-kernel_version/Documentation/sysctl/ — A directory containing a variety of sysctl tips, including modifying values that concern the kernel (kernel.txt), accessing file systems (fs.txt), and virtual memory use (vm.txt).
/usr/share/doc/kernel-doc-kernel_version/Documentation/networking/ip-sysctl.txt — A detailed overview of IP networking options.
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| Revision 4-1 | Tue Dec 6 2011 | ||
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| Revision 4-0 | Mon Oct 3 2011 | ||
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| Revision 3-1 | Wed May 19 2011 | ||
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| Revision 3-0 | Tue Mar 22 2011 | ||
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| Revision 2-0 | Tue Nov 09 2010 | ||
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| Revision 1-0 | Mon Nov 16 2009 | ||
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