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3.3. Updating Packages from the Command Line with yum

The foundation of the Package Updater is the Yum package manager, developed by Duke University to improve the installation of RPMs. yum searches supported repositories for packages and their dependencies so they may be installed together in an effort to alleviate dependency issues. Red Hat Enterprise Linux 5 uses yum to fetch packages and install packages.
up2date is not available on Red Hat Enterprise Linux 5, which uses Yum (Yellowdog Updater Modified). The entire stack of tools that installs and updates software in Red Hat Enterprise Linux 5 is now based on Yum. This includes everything from the initial installation via Anaconda installation program to host software management tools like pirut.

3.3.1. yum Commands

yum commands are typically typed as the following: 
yum command [package_name]
By default, Yum will automatically attempt to check all configured repositories to resolve all package dependencies during an installation or upgrade. The following is a list of the most commonly-used yum commands. For a complete list of available yum commands, refer to man yum.
yum install package_name
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 wildcard, and any matches are then installed.
yum update package_name
Used to update the specified packages to the latest available version. If no packages are specified, then yum will attempt to update all installed packages.
If the --obsoletes option is used (i.e. yum --obsoletes package_name), yum will process obsolete packages. As such, packages that are obsoleted across 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
Used to remove specified packages, along with any other packages dependent on the packages being removed.
yum provides package_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 supported repositories.
yum localinstall absolute path to filename
Used when using yum to install a package located locally in the machine.