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I've got a rather weird situation. I recently virtualized one of our main servers in the company that had our DNS and Active Directory on it. We've recently found out that an old program on the newly virtualized server isn't functioning as normal so we'd like to revirtualize that server and just that drive to its own VM. We are nervous about reconnecting that server to the network since it had DNS and AD on it. We've uninstalled DNS from the server, renamed the server, and removed its static IP address, so it would get one dynamically.

My assumption would be, at this point reconnecting it to our network couldn't cause any major problems, but I wanted to get everyone's thoughts on that. Are there any other precautions I should take to make sure it doesn't cause any conflicts with our network or our current AD?

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up vote 3 down vote accepted

If I'm understanding your question correctly, you:

  • Had a physical server
  • Made a virtual clone of it using some P2V conversion tool
  • Turned off the physical server and left the virtual one running
  • Found some problems in the virtualized server
  • Now want to turn on again the physical server

If this is your situation, then DON'T DO IT.

If you turn on again what is for all intents and purposes an old copy of a domain controller, then you're going to incur in a USN rollback, which is one of the most unpleasant things that can happen to an Active Directory.

You should turn it on in an isolated network, run dcpromo to remove AD from it, change its name and IP address, and only then connect it again to your network. Unfortunately, you can't be sure your application is going to suvive such massive changes on the server...

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+1 - Don't plug an old DC that's been disconnected back into the LAN until you get Active Directory off of it. Having said that, you're probably going to have a tough time getting AD off of it. You can't just re-join the domain as a member server, so you're going to have to connect the machine to an isolated network, reinstall DNS and "point" it at itself, seize all the FSMO roles, use DCPROMO to demote it as the last domain controller in its domain (which will put the machine in a "workgroup") and then, finally, you'll be able to attach it to the production LAN and re-join it to the domain. – Evan Anderson Jun 29 '11 at 21:37

If you clone a server, which is essentially what you're doing, you need to sysprep it other wise bad things will happen. You should also remove Active Directory from it as well, along with everything else that isn't that application.

All of that being said, I still wouldn't recommend this. You should probably contact the vendor of that program and find out the recommended migration path from them.

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And don't run it on a DC, if you can help it. – mfinni Jun 29 '11 at 21:10

DNS doesn't worry me unless some client decides to point to it for DNS (which you can control). You should run dcpromo to demote the server from acting as an AD server BEFORE connecting it to the network.

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