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The configuration file for 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 can also contain one or more [repository] sections, which allow you to set repository-specific options. However, it is recommended to define individual repositories in new or existing .repo files in the /etc/yum.repos.d/ directory. The values you define in individual [repository] sections of the /etc/yum.conf file override values set in the [main] section.

This section shows you how to:

  • set global Yum options by editing the [main] section of the /etc/yum.conf configuration file;

  • set options for individual repositories by editing the [repository] sections in /etc/yum.conf and .repo files in the /etc/yum.repos.d/ directory;

  • use Yum variables in /etc/yum.conf and files in the /etc/yum.repos.d/ directory so that dynamic version and architecture values are handled correctly;

  • add, enable, and disable Yum repositories on the command line; and,

  • set up your own custom Yum repository.

8.4.1. Setting [main] Options

The /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.

A sample /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

The following are the most commonly-used options in the [main] section:

assumeyes=value

where value is one of:

0yum 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=directory

where directory 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.

debuglevel=value

where value 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=value

where value 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]

This option allows you to exclude packages by keyword during installation/updates. Listing multiple packages for exclusion can be accomplished by quoting a space-delimited list of packages. Shell globs using wildcards (for example, * and ?) are allowed.

gpgcheck=value

where value 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.

If this option is set in the [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=value

where value is one of:

0yum 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.

1yum should check the dependencies of each package when removing a package group, and remove only those packages which are not required by any other package or group.

installonlypkgs=space separated list of packages

Here you can provide a space-separated list of packages which yum can install, but will never update. See the yum.conf(5) manual page for the list of packages which are install-only by default.

If you add the 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=value

where value is an integer representing the maximum number of versions that can be installed simultaneously for any single package listed in the installonlypkgs directive.

The defaults for the 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=value

where value 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_name

where file_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=value

where value 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 i686 and AMD64 versions of a package, if both were available.

obsoletes=value

where value 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=value

where value is one of:

0 — Disable all Yum plug-ins globally.

Disabling all plug-ins is not advised because certain plug-ins provide important 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=directory

where directory 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=value

where value 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.

For a complete list of available [main] options, see the [main] OPTIONS section of the yum.conf(5) manual page.

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What is the conf t command?

Next, type config terminal (or config t) to go to global configuration mode (where the prompt looks like router(config)# ).

What is line console password?

1. Console Password : It is used to set the console port password, if no password has been set on the router's console, by default, the user can use the access user mode. The real encryption process ensues when a password is configured or the existing configuration is written.

What is in and out in access

In–when you are running traffic coming INTO the interface through an ACL. Out–when you are running traffic leaving the interface through an ACL. If you want to filter packets that is coming in, you want to use the in; and if you want to filter packets that is coming out then you use the out.

What is the use of line Vty 0 4?

By default five vty lines (0–4) are open. You can open additional lines using the line vty command. Once lines are open, login is enabled by default. Before users can access the lines, you must configure a password, disable login using the no login command, or configure AAA authentication on the lines.