Why CentOS?
CentOS (CentOS.org) is a rebuild/recompile of the Red Hat Enterprise Linux 3 code and is free to use. It is a great performer with cPanel, and as it is free, usually a much better alternative to RHEL.

The following tutorial is intructions on upgrading from just about any Red Hat release (below Fedora) to CentOS. This tutorial is specifically dealing with Red Hat 9 and CentOS 3.4.

As with any upgrade on a production server is is highly recommended to backup your data.

You will need to download and install Yum for this. You can download yum from: http://linux.duke.edu/projects/yum/download.ptml

You may also want to rebuild your RPM database:

rpm -vv --rebuilddb

You should update your /etc/yum.conf to look something like the following:

[main]
exclude=mod_ssl* httpd* perl mysql* php* #add this line for cpanel servers
cachedir=/var/cache/yum
debuglevel=2
logfile=/var/log/yum.log
pkgpolicy=newest
distroverpkg=redhat-release
tolerant=1
exactarch=1

[base]
name=CentOS-$releasever - Base
baseurl=http://beta.centos.org/centos/$releasever/os/$basearch/
gpgcheck=1

#released updates
[update]
name=CentOS-$releasever - Updates
baseurl=http://beta.centos.org/centos/$releasever/updates/$basearch/
gpgcheck=1

#packages used/produced in the build but not released
[addons]
name=CentOS-$releasever - Addons
baseurl=http://beta.centos.org/centos/$releasever/addons/$basearch/
gpgcheck=1

#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras
baseurl=http://beta.centos.org/centos/$releasever/extras/$basearch/
gpgcheck=1

#centosplus repo - updated packages that extend beyond rhel release versions
#run auto update with this repo enabled only if you know you want extended functonality
#[centosplus]
#name=CentOS-$releasever - CentOSplus
#baseurl=http://beta.centos.org/centos/$releasever/centosplus/$basearch/
#gpgcheck=1

#packages in testing
#[testing]
#name=CentOS-$releasever - Testing
#baseurl=http://beta.centos.org/centos/$releasever/testing/$basearch/
#gpgcheck=1

 

You may want to adjust the URLs to pickup from a mirror closest to you, mirrors are available at centos.org.

Import the GPG key for CentOS 3.4 rpms:

rpm --import http://mirror.centos.org/centos/3.4/os/i386/RPM-GPG-KEY-CentOS-3

Start the upgrade via yum:

yum upgrade

This will take a while, and time varies depending on your connection speed. Be sure to check on progress as you will be prompted several times if you wish to continue.

You will want to check if your kernel has been properly installed and added to your bootloader.

If all looks ok you can go ahead and restart your computer:

reboot

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