First candidates: my 2 Domain Controllers. There are good reasons for upgrading your Domain Controllers. I have been presenting about this multiple times over the last couple of months. One of the great features of Domain Controllers on Windows Server 2012 is of course the virtualization-safe features of this version: on a supported hypervisor (read: Windows Server 2012), you can now safely virtualize your DCs without having to be afraid that some uninformed system administrator is going to snapshot the machine, or, even worse, apply the snapshot. Doing so might cause nasty things like USN bubbles, inconsistent passwords, duplicate SIDs and the like.
Both machines run Windows Server 2008 R2 Server Core. A quick look at TechNet didn't reveal anything prohibiting the upgrade so I went along after making a quick last backup before the upgrade.
After being greeted by the installation wizard and indicating all my choices (realizing that upgrading won't allow you at install time to move from server core to GUI), the compatibility wizard ran. This was the result:
As you can see, unsurprisingly the necessary support files for preparing schema etc. are not available on the Domain Controller. To overcome this, head over to the Windows Server 2012 DVD and navigate to the "support" folder. In here you will find good old trusted adprep.exe. Note that in this version, adprep is now actually a PowerShell wrapper that will perform the same pre-requisites tests and checks as the new DCPromo that is now rolled into Server Manager. This means e.g. that you no longer need to worry from which DC you are actually running adprep (or DCPromo); this is all being taken care of for you.
(to be continued ...)