The first time I tried to do this via the Windows Server Backup GUI, I was surprised that I couldn't backup just the system state on a Domain Controller.
Turns out you need to hit the command line (bit of a reoccurring theme in Windows 2008).
the command to use is :
Running it from the command line with no options gives us a bit of help:
So how do we backup the system state only?
WBADMIN START SYSTEMSTATEBACKUP -backuptarget:d:
Problem here is that C: is my System Drive and my DIT rests on my D: drive, which means I get the following error message
No extra disks to backup onto, no CDR/DVD drive to backup onto and out of the box WBADMIN will not allow a backup to a UNC path or mapped drive!
However all is not lost!
KB944530 points out that we can backup onto local volumes by tweaking the registry as follows:
Data type: DWORD
Value data: 1
Running the same command again works: