/etc/yum.conf

The /etc/yum.conf file is the main configuration file for the YUM (Yellowdog Updater, Modified) package manager, used in Red Hat-based Linux distributions such as Fedora, CentOS, and RHEL. This file contains global configuration options that control the behavior of the YUM package manager.

Structure of /etc/yum.conf

The /etc/yum.conf file is a plain text file and is usually divided into sections, with each section containing key-value pairs. The most common section is [main], which defines global settings.

Example /etc/yum.conf

Here is an example of what the /etc/yum.conf file might look like:

[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

Key Directives in /etc/yum.conf

• cachedir: Specifies the directory where YUM stores downloaded packages and cache data. The $basearch and $releasever variables are automatically replaced with the appropriate architecture and release version of the distribution.

  cachedir=/var/cache/yum/$basearch/$releasever

• keepcache: Determines whether YUM should keep the cache of packages after installation. Set to 0 to remove cached packages after installation, and 1 to keep them.

  keepcache=0

• debuglevel: Sets the level of debugging information in the YUM output. Ranges from 0 (no debugging) to 10 (most verbose).

  debuglevel=2

• logfile: Specifies the path to the log file where YUM logs its actions.

  logfile=/var/log/yum.log

• exactarch: When set to 1, YUM will only install packages that match the system's architecture.

  exactarch=1

• obsoletes: When set to 1, YUM will allow obsoleting of packages. This is useful for distribution upgrades.

  obsoletes=1

• gpgcheck: When set to 1, YUM will perform a GPG signature check on packages to ensure their authenticity and integrity.

  gpgcheck=1

• plugins: When set to 1, YUM will enable the use of YUM plugins.

  plugins=1

• installonly_limit: Limits the number of versions of each package that can be installed simultaneously. This is particularly useful for limiting the number of kernel versions on the system.

  installonly_limit=3

Additional Configuration Options

• exclude: Excludes specific packages from being installed or updated.

  exclude=package1 package2

• includepkgs: Only includes specified packages for installation or updates.

  includepkgs=package1 package2

• proxy: Specifies a proxy server to use for HTTP and HTTPS connections.

  proxy=http://proxy.example.com:8080

• proxy_username and proxy_password: Credentials for the proxy server.

  proxy_username=myusername
  proxy_password=mypassword

Managing Repositories

In addition to the global configuration in /etc/yum.conf, YUM repositories are typically defined in separate .repo files located in the /etc/yum.repos.d/ directory. Each repository file contains configuration options specific to that repository.

Example Repository File

Here is an example of a repository configuration file /etc/yum.repos.d/example.repo:

[example-repo]
name=Example Repository
baseurl=http://repo.example.com/centos/$releasever/os/$basearch/
enabled=1
gpgcheck=1
gpgkey=http://repo.example.com/RPM-GPG-KEY-example

Conclusion

The /etc/yum.conf file is an essential configuration file for the YUM package manager, allowing you to control various global settings for package management on Red Hat-based systems. Understanding and configuring this file correctly can help optimize your system's package management processes.