Backup and restore a whole Red Hat Enterprise Linux system
Red Hat does not support in-place upgrades between major versions 5 and 6 of Red Hat Enterprise Linux. (A major version is denoted by a whole number version change.
For example, Red Hat Enterprise Linux 5 and Red Hat Enterprise Linux 6 are both major versions of Red Hat Enterprise Linux).
In-place upgrades across major releases do not preserve all system settings, services or custom configurations. Consequently, Red Hat strongly recommends fresh installations when upgrading from one major version to another.
You can refer the below knowledge base to backup and restore a whole Red Hat Enterprise Linux system with the dump/restore commands.
How to backup and restore a whole Red Hat Enterprise Linux system with the dump/restore commands?
Q] Also, do we need to get different licenses for this new server?
A] No, you do not need a different license as you are going to format the existing system. So you can use the same license to register the newly built machine.
Before formatting the old system execute the below commands to unregister and unsubscribe:
# subscription-manager remove --all
# subscription-manager unregister
# subscription-manager clean