Upgrade Red Hat 4 to CentOS 4

1) Download necessary packages from centos vault repository
wget http://vault.centos.org/4.9/os/x86_64/centos-release-4-8.x86_64.rpm
wget http://vault.centos.org/4.9/os/x86_64/python-elementtree-1.2.6-5.el4.centos.x86_64.rpm
wget http://vault.centos.org/4.9/os/x86_64/python-sqlite-1.1.7-1.2.1.x86_64.rpm
wget http://vault.centos.org/4.9/os/x86_64/python-urlgrabber-2.9.8-2.noarch.rpm
wget http://vault.centos.org/4.9/os/x86_64/sqlite-3.3.6-2.x86_64.rpm
wget http://vault.centos.org/4.9/os/x86_64/yum-2.4.3-4.el4.centos.noarch.rpm
wget http://vault.centos.org/4.9/os/x86_64/yum-metadata-parser-1.0-8.el4.centos.x86_64.rpm

2) import gpg-keys
rpm --import http://vault.centos.org/4.9/os/x86_64/RPM-GPG-KEY
rpm --import http://vault.centos.org/4.9/os/x86_64/RPM-GPG-KEY-centos4

3) remove redhat-release package with nodeps option
rpm -e --nodeps redhat-release

4) upgrade packages
rpm -Uvh *.rpm

5) replace CentOS-Base.repo file in /etc/yum.repos.d
wget http://vault.centos.org/4.9/CentOS-Base.repo -O /etc/yum.repos.d/CentOS-Base.repo

6) upgrade to centos 4.9
yum update