I’m finally getting around to rebuilding my Server 2012 lab, having a mix of RC and Beta builds that will time bomb soon. A clean install of everything would be ideal but I’m feeling lazy and want to leave my existing settings and configurations in place. For my last lone 2012 Beta install, which is unfortunately my domain controller, I’ll have to rebuild, but for my RC installs I can upgrade. Although natively this process would fail and not officially supported by MSFT as an upgrade path, this can be done. Obviously this applies only to test environments as surely no one would run a non RTM OS build in production anyway.

The key is to edit the cversions.ini file in the sources folder of your installation media. Change the value of the “MinServer=” line to 8400.0 (the last RC build). This tells the upgrade installer that it’s ok to have at least the RC build for an in place upgrade. Otherwise the upgrade will fail.

To upgrade you must launch the installer from within the OS not via booting the media. If you forget and try the latter, the installer will kindly direct you to reboot and try again using the proper method. Unfortunately, this doesn’t work for Beta builds but you’ll probably want to upgrade those to fresher bits anyway.

For more info check out Ivo Beerens post here.