Windows Server 2008 systems with the Active Directory Domain Services role installed have an extra element of functionality (compared to previous versions of Windows Server) in the "stoppable" services for the domain.
This works by Active Directory Domain Services being explicitly enumerated in the Services applet of the Control Panel. One of my pet peeves in Windows is services that do not permit the processing of a stop and start command. Terminal Services is the holdout, as Active Directory can now be explicitly stopped.
Active Directory Domain Services is managed as NTDS in the Services applet. You would use NTDS if you were using the sc command to manage Active Directory. You can also manage these services interactively. Figure A shows Active Directory being stopped on a Windows Server 2008 domain controller.
Figure A
Click the image to enlarge.
Exercise caution
While this functionality is good for Windows administrators, you need to exercise caution. The first thing you should understand is what happens when Active Directory is stopped.
In environments with multiple domain controllers, the other systems would process logon requests. If there are any roles on the server with the stopped services, they will resume when Active Directory is resumed. If the outage will be for an extended period of time, it would be a good idea to transfer the role to another domain controller.
For normal maintenance, such as applying Windows updates or basic hardware maintenance, going without the role for a short amount of time is usually fine.
Also consider this question: Just because you can stop Active Directory, should you? I'm going to wait until Windows Server 2008 R2 before fully upgrading Active Directory because of some of the new features, and it will fit my timeline better.