Migration of CentOS-3 to CentOS-5

1. Direct Upgrades Are Not Supported

As of 2007-04-12, an anaconda or yum upgrade is completely unsupported. As time progresses we will see what can be done.. but currently the best way to do migrate from CentOS-3 to CentOS-5 is the following:

1.1. Safest Migration

• Bring up a second system with CentOS-5
• Port over applications and data from CentOS-3 to CentOS-5 looking for application syntax and operational differences.
• Take down old system and move to new system

1.2. Riskier Migration

• Backup the system to alternative media (USB diskdrive, etc).
• Do a fresh install of CentOS-5
• Find out which applications work from old data.

1.3. Living on the Edge

Anaconda has an option which can be used to force the installer to recognize and try to upgrade an existing installation. In order to use it, you must pass the option upgradeany to the installer. Several known issues (not necessarily all of them !) when using this method to migrate from CentOS-3 to CentOS-5:

• SELinux will be activated, but the mandatory policy module is not installed. This will cause the first attempt to boot the freshly installed Centos-5 to fail. Solution:
  1. boot with selinux disabled (add selinux=0 to the kernel command line)
  2. install the selinux-policy-targeted module:

     yum install selinux-policy-targeted 

• A major upgrade of the X Window System has been implemented between Centos-3 and Centos-5. Unfortunately the installer of Centos-5 needs a bit of help in order to perform the transition:
  1. remove the older drivers:

           yum -y remove XFree86\* 

  2. install the newer drivers:

           yum -y install xorg-x11-drivers