Upgrading a Domain Controller from Windows Server 2008 to 2012

When upgrading an Active Directory Domain Controller from Windows Server 2008 (or 2008 R2) to Windows Server 2012, the AD Forest must be upgraded first.  This has to be manually done, as it is not part of the setup process.

To upgrade the AD Forest, right-click on the Command Prompt icon and select “Run as Administrator”.  Insert the Windows Server 2012 DVD (or mount the ISO using a virtual drive) and switch to that drive inside Command Prompt: “cd [Drive letter]: <ENTER>“.

At the command prompt, type “[Drive letter]:supportadprep /forestprep <ENTER>“.  You will be given a warning about how this is not a reversible operation.  Type “C” and hit <ENTER> to continue.  Once this is done, type “[Drive letter]:supportadprep /domainprep <ENTER>“.

After this step is complete, you may proceed with the upgrade to Windows Server 2012.

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8 Replies to “Upgrading a Domain Controller from Windows Server 2008 to 2012”

  1. From what I’m reading on a number of tutorial sites, Windows 2012 updates the schema automatically as needed, and doesn’t require doing so manually. Can you confirm, or elaborate on your information?

      1. Thanks, David. In our case, our 2008 DCs were 32-bit, so in-place upgrades were not an opton. We built a new virtual machine with 2012, which automatically extended the AD schema as part of the promotion processes. Once all FSMOs and services are migrated from the legacy DCs, we’ll demote them and raise the forest and domain functional levels.


  2. By the way at least for me the pathways above were incorrect, adprep is a folder but inside that folder adprep the application is there so I used:
    “[Drive letter]:supportadprepadprep /forestprep “
    “[Drive letter]:supportadprepadprep /domainprep “

  3. I have 2 Active Directory Servers, both 2008 R2. From your instructions I would preform the command line tasks on my primary AD server and then I could reboot that server and upgrade from Server 2008 R2 to 2012 and then once it is booted up and running do I just repeat the process on my other server or do I just reboot it and upgrade?

    1. My understanding is that it would be the latter, as the forest would already be upgraded. I have not done this in a production environment where there are multiple DCs, but it seems that it would be unnecessary to upgrade the forest more than once. However, running the command on the secondary DC shouldn’t cause any problems, since the forest will already be prepared.

      1. Okay so after I run the Schema updater on my server I would update the operating system its self like I would upgrade from Windows XP to Windows 7?

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