Here we add a few additional repositories to Centos 5.
=== install yum priorities ===
First, install the Yum Priority package, which protect the base Centos 5 components from being overwritten.
yum install yum-priorities
Edit the /etc/yum.repos.d/CentOS-Base.repo file, add priority=1 to each of the sections [base], [addons], [updates], [extras]
Update the system and make sure the yum-priorities is working
Should see the output include “loading priorities plugin …… 99999 packages excluded due to repository priority protection”…