We have two DC in our network. Both now work in 2008 R2 mode. I want to remove the one, that was created first. Is it safe just to turn it off or should I do something to promote replica DC to be main one?
How to promote Active Directory domain controller replica to replace the main domain controller?
You would need to run DCPROMO, as suggested, on the DC you want to remove, but first make sure both DCs are running DNS and if this was the first DC you installed, then it probably has your FSMO roles on it - move them first. The DCPROMO procedure may move them for you, but I would consider safer and wiser to manually move them. In addition, make sure the remaining DC is also configured to be a Global Catalog (GC).
Finally, why are you getting rid of it? In general, I recommend you have two DCs per major site and two DCs on your network so that if one fails, your Active Directory isn't completely lost.
It's pretty strange, but DCPROMO on first DC tells me, that it is a last DC in domain. Meanwhile second DC shows in ADUaC console and replicates successfully. Sep 6, 2009 at 22:50
I would suggest running dcdiag on both servers and checking for any failed tests. Sep 7, 2009 at 0:03
It TELLS you it's the last or it ASKS you if it is the last? Can you post a screen shot of the screen with the message? (I've seen people post screenshots - but I've no idea how they do it on this site). Sep 8, 2009 at 0:06
If you run DCPROMO on the first Dc, the DCPROMO process will take care of moving the FSMO roles to the other DC. Make sure that you're AD DNS is integrated and then run DCPROMO, nothing else should be needed.