How do I install the EPEL repo?
 
CentOS v5.3 assumed.
  1. First uninstall yum-protectbase: yum remove yum-protectbase.
  2. Make sure yum-priorities is enabled. Check /etc/yum/pluginconf.d/priorities.conf to see if Enabled=1.
  3. Set the priorities on each repo in /etc/yum.repos.d. The CentOS-Base should have priority 1, rpmforge 2, EPEL and other repos 20-50.
  4. Add the repo: see http://www.cyberciti.biz/faq/rhel-fedora-centos-linux-enable-epel-repo/.