Move Active Directory from 2003 to 2008
The quick answer is to use dcpromo to add the 2008 server as a domain controller in the same domain that the 2003 server is in. Once the 2008 server is a DC, you can run dcpromo on the 2003 server to remove it as a domain controller. This will allow you to keep your Active Directory intact, but move the services to another server.
Also, as a general rule, it's highly recommended to have 2 servers be domain controllers (and global catalog servers) for your domain. That way your Active Directory stays up in the event of a failure (or reboot!)
There are lots of good articles from Microsoft and bloggers that describe this process. Here are some links:
2003 to 2008 Active Directory
Upgrading to Windows 2008 Active Directory
Here is a TechNet guide. Probably a good place to start.
Planning to Upgrade Active Directory Domains to Windows Server 2008 AD DS Domains
I have done this many times. There are quite a few things that you need to keep in mind. If you currently only have one DC it might be in your best interest to have two DC's.
Also if you want to have just one instead you will need to install the services that you run on the current DC onto the 2008 DC. These are services such as DNS, and DHCP.
If you currently only run one single 2003 server, then that server also serves as your FSMO role holding server. You will first need to move your FSMO roles to the 2008 server before demoting the 2003 server. If you do not you will have severe problems.
Another service to move will be the Global Catalog. You will need to make the new 2008 server a Global Catalog and make sure the replictation has taken place before demoting the 2003 server.
The steps:
- Install 2008 on the new server.
- DCpromo the new server. Make sure AD is replicating.
- Install DNS, DHCP or any other services that you need.
- Make sure DNS is replicating. Move DHCP to the other server. Make sure it is working.
- Move the FSMO roles to the new 2008 server.
- Once you are sure that all roles and services that the 2003 server is using have been moved and are working properly on 2008 then you can proceed with the DCPromo (demote) of the 2003 server.
Will you be keeping both servers after the domain upgrade? If so, your best bet is to leave the new box as a member server and upgrade the current DC instead. You can use the technet guide at http://technet.microsoft.com/en-us/library/cc731314.aspx for assistance.