To ADPREP or not to ADPREP, and do we need the GPPREP switch
In our step-by-step Screencast, we demonstrate how to upgrade an existing Active Directory domain to windows server 2012, by adding an additional Windows 2012 Domain controller. As you will see, forest and domain preparation is performed automatically when you run the new Active Directory Domain Services configuration wizard.
So far so good. Veterans, with experience in Active Directory upgrades, remember the ADPREP tool which had to be run on legacy Domain Controllers. Microsoft provided two versions of the tool – ADPREP.EXE (x64 version) and ADPREP32.exe (x86 version). Finding and running the correct version definitely complicated the whole upgrade process.
You can still prepare manually an existing Active Directory domain, by running ADPREP and that approach makes sense in a large deployments, with specific requirements and security procedures, related to AD Schema Extensions. In this case, you need to keep in mind that:
- ADprep comes only as a 64 bit version in Server 2012 and is located under the “Support” folder on the installation disk.
Fig.1 ADPrep – available only as x64 version in Server 2012
- If you try to run ADPREP on a legacy Windows Server 2003/2003 R2, you will get the error message “adprep.exe is not a valid Win32 application”, even if the server is running x64 OS.
Fig.2 Error Message “adprep.exe is not a valid Win32 application”, when running ADPREP on Server 2003/2003 R2
- You can run ADPREP remotely from a Windows Server 2012 or Windows 8 (x64 version). The tool connects automatically to the corresponding DC – Schema Master for forestprep, and Infrastructure Master for domainprep. In our demo we perform this operation from our new Server 2012 Domain Controller
Fig.3 Running ADPREP remotely from Server 2012
And here comes the question – Do we need Group Policy Preparation?
This is performed with the GPPREP switch, where the whole command is “adprep.exe /domainprep /gprep”. It is important to note, that when you are using the GUI – Active Directory Domain Services Configuration Wizard:
- Group Policy preparation (GPPREP) is not performed automatically
- You will not get a warning, if you need GPPREP
So, when do we need Group Policy preparation and how do we check if it has been performed?
The short answer is: You don’t need Group Policy preparation, if you’ve never had Windows Server 2000 Domain Controllers in the Domain. Moreover, GPPREP needs to be run only once. If you’ve run GPPREP, when upgrading to Windows Server 2003 or 2008, you don;t need to repeat the process.
The last question is: How do we know, that GPPREP has been performed on the domain?
The rule of thumb here is: If you are not sure, just run the command again.
Fig.4 How to check whether GPPREP is required
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