RHEL to CentOS Migration

Migration from RHEL5 to CentOS5

Copied from: Migration Guide

     "All that you should need to do is install centos-release, remove redhat-release rpms 
     and just yum update the machine, which should bring in all packages changed by 
     CentOS ( since they will have a slightly higher E-V-R )." - per KaranbirSingh on centos-list
         You may also wish to remove the "rhnplugin" from yum (not necessary but gives an error msg) 
   
     OR - per Craig White on centos-list Mon, 29 Oct 2007 (updated for 5.4)...

     # 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-5-4.el5.centos.1.i386.rpm  \
       http://mirror.centos.org/centos/5/os/i386/CentOS/centos-release-notes-5.4-4.i386.rpm \
       http://mirror.centos.org/centos/5/os/i386/CentOS/redhat-logos-4.9.99-11.el5.centos.noarch.rpm 
     # yum update

   * Sometime the rpm install using a URL may be problematic. In that case use wget or lftpget to 
     get local copies of the files and install with "rpm -ivh ...". 

 Note: It is only possible to pull the lastest 'point release' packages directory from the 
         host: mirror.centos.org Older point release packages are relocated to: vault.centos.org 
         and so for the foregoing example, we would use:

     # cp /etc/redhat-release /etc/redhat-release-saved
     # rpm -e --nodeps redhat-release-notes redhat-release yum-rhn-plugin redhat-logos
     # rpm -ivh \
       http://vault.centos.org/5.0/os/i386/CentOS/centos-release-5-0.0.el5.centos.2.i386.rpm  \
       http://vault.centos.org/5.0/os/i386/CentOS/centos-release-notes-5.0.0-2.i386.rpm

Installing yum

Copied from: CentOS Tips and Tricks

Okay, okay -- I get it -- it is not CentOS. But, I still want yum, or to try to remove and repair a crippled set of yum configurations.

First, take full backups and make sure they may be read. This may not work.

Then, you need the following package to get a working yum - all of which can be downloaded from any CentOS mirror:

   * centos-release 

You should already have this package installed. You can check that with

 rpm -q centos-release
 centos-release-4-4.3.i386

If it is already on your system, please check that the yum configuration hasn't been pulled and is available on your system:

 ls -l /etc/yum.repos.d/

This directory should contain only the files: CentOS-Base.repo and CentOS-Media.repo. If those aren't there, you should make a directory: 'attic' there, and 'mv' a backup of the current content into that attic, to prepare for the reinstall of the centos-release package:

 rpm -Uvh --replacepkgs centos-release.*.rpm

If centos-release isn't installed on your machine, you can drop the --replacepkgs from the command above. Make a backup directory ./attic/ and move any other files present into it, so that you can back out of this proccess later, if you decide you are in 'over your head'.

Then you need the following packages:

CentOS 4 (available from where you also got the centos-release package):

   * yum
   * sqlite
   * python-sqlite
   * python-elementtree
   * python-urlgrabber 

CentOS 5 (available from where you also got the centos-release package):

   * m2crypto
   * python-elementtree
   * python-sqlite
   * python-urlgrabber
   * rpm-python
   * yum 

Download those into a separate directory and install them with

 rpm -Uvh *.rpm

from that directory. As before, take a backup of /etc/yum.conf so that you might back out any changes.