yum is software installation tool for Red Hat Linux and Fedora Linux. yum commands are typically run as yum <command> <package name/s>. By default, yum will automatically attempt to check all configured repositories to resolve all package dependencies during an installation/upgrade.

Here is a list of the most common and used yum commands:

yum list all

To list all packages that are available to use the yum command.

yum install <package name/s>

Used to install the latest version of a package or group of packages. If no package matches the specified package name(s), they are assumed to be a shell glob, and any matches are then installed.

yum update <package name/s>

Used to update the specified packages to the latest available version. If no package name/s are specified, then yum will attempt to update all installed packages.

If the –obsoletes option is used (i.e. yum –obsoletes <package name/s>, yum will process obsolete packages. As such, packages that are obsoleted accross updates will be removed and replaced accordingly.

yum check-update

This command allows you to determine whether any updates are available for your installed packages. yum returns a list of all package updates from all repositories if any are available.

yum remove <package name/s>

Used to remove specified packages, along with any other packages dependent on the packages being removed.

yum provides <file name>

Used to determine which packages provide a specific file or feature.

yum search <keyword>

This command is used to find any packages containing the specified keyword in the description, summary, packager and package name fields of RPMs in all repositories.

yum localinstall <absolute path to package name/s>

Used when using yum to install a package located locally in the machine.

More info under:

http://www.centos.org/docs/5/html/5.1/Deployment_Guide/s1-yum-useful-commands.html

http://yum.baseurl.org/wiki/YumCommands