A. Server 2008 R2 introduces some new Active Directory (AD) functionality, and you must prepare both the domain and forest before you introduce a Server 2008 R2 DC.
If you already have Server 2008 DCs, you just need to run the commands
adprep /domainprep
and
adprep /forestprep
If you're running Windows 2003 DCs, you also need to run command
adprep /domainprep /gpprep
If you want to introduce RODC's (Server 2008 or 2008 R2), you also need to run
adprep /rodcprep
You can find adprep in the support\adprep folder of the 2008 R2 media. You should copy this folder to the C: drive of the local computer and execute adprep from the local folder. Remember that you must be a schema admin to run the forestprep update and you should run it on the schema master DC. You must be a domain admin to run domainprep, which should be run on the infrastructure master of the domain.
Related Reading:
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