Is backup from CentOS 5.7 and restore on CentOS 6.x allowed?

Generally, that should be no problem. Virtualmin backups are intended to be OS independent, and surely independent from such a small version jump. Presuming of course the Virtualmin setup is not totally different, like storing user emails or databases elsewhere.

Of course, the devil is in the details (e.g. the new system might be missing some PHP features or so), so to better be safe than sorry you should do a test run with this before you do it on a live system.

Howdy,

Also, there's some docs that can walk you through performing a migration available here:

http://www.virtualmin.com/documentation/system/migrate

Yep, that migration guide Eric mentioned lists "reduce DNS zone TTL" as one step of the progress.

Normally that would be all valid, in case the migration includes a change of IP addresses. In your case though, where I assume the host and IP stays the same, that's not required.

Aside from that, the guide basically boils down to "take backups (make sure to include Virtualmin settings), install new OS, install Virtualmin, restore backups". :) So it should work this way. Testing is required though, like the guide also mentions.

Howdy,

Migrating CentOS 5 to CentOS 6 will work -- you'll just need to plan for some downtime so that you can troubleshoot any issues that come up.

I might suggest installing CentOS 6 into a Virtualbox instance on your desktop, before doing the actual migration... and then as a test, installing the backups into it. That would allow you to do some testing, before wiping out your setup on your live server.

-Eric