The software vendor that we used has always specified that we should load RHEL on servers we've bought to run their software however they did start to accept CentOS and even now prefer it on new installs.
Anyway we have some servers running Red Hat Enterprise Linux Server release 5.3 (Tikanga) that have never had a RHN subscription, so basically they're exactly the same as what they were the day we loaded it.
Is it possible to convert these straight over to a new CentOS?
Edit: Ok so from reading more, it seems RHEL 5 can only be migrated to CentOS 5 and then I would need to do the updates to a newer version. It seems pretty straight forward, not even requiring a reboot. Here is the instructions I've found:
# 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-5-8.el5.centos.i386.rpm \
http://mirror.centos.org/centos/5/os/i386/CentOS/centos-release-notes-5.8-0.i386.rpm \
http://mirror.centos.org/centos/5/os/i386/CentOS/redhat-logos-4.9.99-11.el5.centos.noarch.rpm
# yum update
Is it really that simple to switch from RHEL to CentOS?