"...yum is built on the Python programming language, which is a
building block for the Red Hat/Fedora distributions. While current
support is limited to the Red Hat/Fedora/Yellow Dog/Mandriva/Asp
distributions, per the latest available Netcraft survey, that's
over half the Linux market. If you want to learn patch management
for Linux, you need to know how to use yum and configure, or
'yummify,' associated repositories.
"The simplest way to configure a yum repository is to mirror one
that already exists. Most Fedora repositories already support yum.
But you do not have to mirror the entire repository, because much
of it is built from installation CDs. In addition, as packages
change, or if you combine packages from different mirrors, you may
prefer to create yum headers on your own system rather than
download them from a remote mirror..."