Please note this tutorial has not been tested, but in theory should work.

The following tutorial provides the few steps to upgrade Red Hat 9 to CentOS 4:

1. Make a full backup of your data.

2. Import GPG keys:
Code: 
rpm --import http://beta.centos.org/centos/4.0beta/os/i386/RPM-GPG-KEY
rpm --import http://beta.centos.org/centos/4.0beta/os/i386/RPM-GPG-KEY-centos4.0beta
3. Install/Upgrade yum:
Code: 
rpm -Uvh --nodeps http://beta.centos.org/centos/4.0beta/os/i386/CentOS/RPMS/yum-2.1.13-2.centos4.noarch.rpm
4. Upgrade the release:
Code: 
rpm -i http://beta.centos.org/centos/4.0beta/os/i386/CentOS/RPMS/centos-release-4.0beta-5.i386.rpm
5. Have yum update your OS:
Code: 
yum upgrade

The following tutorial provides the few steps to upgrade Red Hat 9 to CentOS 3.4:

1. Make a full backup of all your data

2. Import GPG Keys:
Code: 
rpm --import http://beta.centos.org/centos/3.4/os/i386/RPM-GPG-KEY-CentOS-3
3. Install/Upgrade yum:
Code: 
rpm -Uvh --nodeps http://beta.centos.org/centos/3.4/os/i386/RedHat/RPMS/yum-2.0.8-1.centos.7.noarch.rpm
rpm -Uvh --nodeps http://beta.centos.org/centos/3.4/os/i386/RedHat/RPMS/centos-yumconf-1-11.noarch.rpm
rpm -Uvh --nodeps http://beta.centos.org/centos/3.4/os/i386/RedHat/RPMS/centos-yumcache-3.1-0.20050105.3.noarch.rpm
4. Upgrade the release:
Code: 
rpm -i http://beta.centos.org/centos/3.4/os/i386/RedHat/RPMS/centos-release-3-4.2.i386.rpm
5. Have yum update your OS:
Code: 
yum upgrade
Areon Reviewed by Areon on . Upgrading Red Hat 9 to CentOS 3.4 or 4 Please note this tutorial has not been tested, but in theory should work. The following tutorial provides the few steps to upgrade Red Hat 9 to CentOS 4: 1. Make a full backup of your data. 2. Import GPG keys: rpm --import http://beta.centos.org/centos/4.0beta/os/i386/RPM-GPG-KEY rpm --import http://beta.centos.org/centos/4.0beta/os/i386/RPM-GPG-KEY-centos4.0beta Rating: 5