Hi,

I am having three servers
1. Centos 5.5
2. OpenSUSE 11.1
3. Fedora 12

I want to migrate the servers to RedHat 6, please let me know the process i follow to migrate them to Redhat6.

Regards
ViVek

You don't. You save any valuable data on them and reinstall. Whilst is it *possible* to migrate from centos5 to rhel6, you still should NOT do this if you are serious about administering these systems responsibly and appropriately.

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Agree with acid_kewpie. Back up your data, build new servers, and put your data back on them. But since you're using RHEL 6, you're paying for support, with your RHEL subscription, right? Give RedHat support a call...they may have some ways to make it easier.

In addition to the other comments: there's really not enough info here to provide useful guidance. Are these each standalone servers that only access local disk, or are they mounting SAN / NAS volumes? Do you have new servers that you'll be migrating to, or are you expected to reuse the existing hardware? Are these running high-activity production services, or are these a bunch of tinkering boxes in your garage?

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i am using servers with two 6 core xeon servers with 32 GB RAM on each server.
once the servers are migrated we are going to implement HA on them with al the running infrastructure services like Samba(LDAP),Apache, Tomcat, DNS, svn, git, IP, FTP and other services with Master and slave LDAP.

Concur with acid_kewpie & TB0ne: start afresh or you'll regret it

There is one exception to install a new OS, while it won’t safe you a backup in case something goes wrong: in case you have all your valuable data in one dedicated partition like /home, you can reformat and install any new Linux in the other partitions you use for the OS. Care must be taken not to reformat the wrong partiton during installation though, but when it succeeds you just mount the old /home afterwards again and continue.

Ok...then I'd definitely contact RedHat support, and see what tips they have for you, to make sure things work correctly.

If the servers are currently in use, the safest/easiest way to do it would be to shut them down, pull the hard drives, and put in new, blank ones. Build the new systems on them, and go forward. If something goes wrong, you put the old drives back in, and power up. Hard drives are cheap, you KNOW your old data is in pristine condition, and you can easily spend another $30 or so on an external drive enclosure, to make those drives become USB attachable, for later use.