How to Migrate from RHEL5 to CentOS5...

# cp /etc/redhat-release /etc/redhat-release-saved
# rpm -e --nodeps redhat-release-notes redhat-release \
yum-rhn-plugin redhat-logos
# rpm -ivh \
http://mirror.centos.org/centos/5/os/i386/\
CentOS/centos-release-5-5.el5.centos.1.i386.rpm  \
http://mirror.centos.org/centos/5/os/i386/\
CentOS/centos-release-notes-5.5-0.i386.rpm \
http://mirror.centos.org/centos/5/os/i386/\
CentOS/redhat-logos-4.9.99-11.el5.centos.noarch.rpm
# yum update