There is no specific document, procedure defined to perform this. Cloning DC's should be performed in a testing environment, and should not be tried with an ongoing DC. DC clonings are completely dependant on your DNS setup because of which, for some it works and for some, it doesn't.

I would suggest the below overview for cloning DC.

1. Initially setup a test-DC and perform cloning and look for the challenges you face in your environment.

2. For a production DC cloning, create an Additional DC (vm or physical) and transfer FSMO roles and GC as required.(For me this worked).

3. Try Physical to Virtual (using converter) or Virtual to Virtual (simple clone), depending on your setup.

4. If ADC (physical) is good and syn'c fine with PDC....Try performing a cloning for ADC using converter.

else

5. Setup a simple 2003 server vm, similar to your AD box...and perform a AD restore (directory services and registry hives) using softwares like (CA Arcserve Backup, Commvault Galaxy, Symantec Backupexec etc).

Note: for this you need to follow the pre-requisites for restoring AD specific to the product you want to use for restoring.