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1.3. Configuring Yum and Yum Repositories

This section shows you how to:
The /etc/yum.conf configuration file contains one mandatory [main] section under which you can set Yum options. The values that you define in the [main] section of yum.conf have global effect, and may override values set any individual [repository] sections. You can also add [repository] sections to /etc/yum.conf; however, best practice is to define individual repositories in new or existing .repo files in the /etc/yum.repos.d/directory. Refer to Section 1.3.2, “Setting [repository] Options” if you need to add or edit repository-specific information.

1.3.1. Setting [main] Options

The /etc/yum.conf configuration file contains exactly one [main] section. You can add many additional options under the [main] section heading in /etc/yum.conf. Some of the key-value pairs in the [main] section affect how yum operates; others affect how Yum treats repositories. The best source of information for all Yum options is in the [main] OPTIONS and [repository] OPTIONS sections of man yum.conf.
Here is a sample /etc/yum.conf configuration file: 
[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
Here is a list of the most commonly-used options in the [main] section, and descriptions for each:
assumeyes=<value>
...where <value> 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=/var/cache/yum/$basearch/$releasever
This option specifies the directory where Yum should store its cache and database files. By default, Yum's cache directory is /var/cache/yum/$basearch/$releasever. See Section 1.3.3, “Using Yum Variables” for descriptions of the $basearch and $releasever Yum variables.
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; i.e., you can enable GPG-checking on one repository while disabling it on another. Setting gpgcheck=<value> for an individual repository in its correpsonding .repo file overrides the default if it is present in /etc/yum.conf. Refer to Section 3.3, “Checking a Package's Signature” for further information on GPG signature-checking.
groupremove_leaf_only=<value>
...where <value> 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.
For more information on removing packages, refer to Smart package group removal.
installonlypkgs=<space> <separated> <list> <of> <packages>
Here you can provide a space-separated list of packages which yum can install, but will never update. Refer to man yum.conf 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 man yum.conf. 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. Refer to installonly_limit=<value> for details on the installonly_limit directive.
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=/var/log/yum.log
This option specifies where yum should send 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 i586 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 plugins globally.

Disabling plugins is not advised

Disabling all plugins is not advised because certain plugins provide important Yum services. In particular, rhnplugin enables connecting to Red Hat Network, and the security plugin allows system administrators to easily update the system with (sometimes critical) security updates. Disabling plugins globally is provided as a convenience option, and is generally only recommended when diagnosing a potential problem with Yum.
1 — Enable all Yum plugins globally. With plugins=1, you can still disable a specific Yum plugin by setting enabled=0 in that plugin's configuration file. Refer to Section 1.4, “Yum Plugins” for more information about various Yum plugins, or to Section 1.4.1, “Enabling, Configuring and Disabling Yum Plugins” for further information on controlling plugins.
reposdir=</absolute/path/to/directory/containing/repo/files>
This option allows you to specify a directory where .repo files are located. All .repo files contain repository information (similar to the [repository] section(s) 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. Refer to Section 1.3.2, “Setting [repository] Options” for more information about options you can use for both the [repository] section and .repo files. 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.