Provided you follow all the general procedures for upgrading your DCs to Server 2008, prepare your domain correctly using ADPrep and enable replication to take place fully between each of the major steps, you shouldn't have too many issues. The main problem I have is the transfer of data shares which are on the old server to the new server, as obviously the new server will need a different name on your network, and as such, shortcuts, network share paths and so on will no longer work once the shares are moved.
The general procedure for an Active Directory migration is below. My only piece of advice is to allow yourself enough time for the procedure to take place, and don't rush anything, and you'll be fine.
N.B. The procedure below does not include the migration of WINS. This has been demoted to a 'Feature' in Server 2008 - which you install from the 'Server Manager' > 'Features' > 'Add Feature' window. The majority of the other features, such as DNS, are still 'Roles' and are installed from the 'Add Roles' pane in the 'Roles' section of Server 2008's Server Manager applet.
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Install Windows Server 2008 onto the new server which is intended to be promoted as a Domain Controller. Ensure the new server is assigned a routable static IP address on your IP subnet. Ensure the IP address is not included in any of your existing DHCP scopes. The only DNS server entry at this stage should be the IP address of the existing domain controller on your network.
After installation, join the new machine to the existing domain as a member server. This procedure is exactly the same as joining a workstation to the domain.
Since you are upgrading the Operating System on the new Domain Controller, you will need to add some values to the existing Active Directory schema, in order for the new server to become a Domain Controller. Windows Server 2008 supports more functionality than before, so a schema upgrade for the domain and forest is required to facilitate this and make this new feature set fully functional on the domain. To make the necessary changes, you must be logged on as the built-in Administrator user account, or a user with Domain, Schema and Enterprise Admin privileges.
Insert the Windows Server 2008 media into your current server . Open a command prompt and browse to sources\adprep folder within the Windows Server 2008 DVD media. Execute the command adprep /forestprep.
Next, execute adprep /domainprep . You must be logged on as a Domain Admin user for these steps to work correctly. Once these commands have run your Active Directory schema will have been extended to support Windows Server 2008 as a Domain Controller.
Promote the new server as a Domain Controller for the domain. Enter dcpromo at a command prompt and follow the wizard. When prompted, select the option for an additional domain controller in an existing domain. After the wizard completes, the new server will be acting as a Domain Controller for your domain. It is necessary at this point to restart the server for these changes to be applied.
In a single-domain Active Directory forest, all servers should also be Global Catalog servers. The Global Catalog is a required component of Active Directory which is used during logins to establish universal group membership for a user account. To promote the new server as a Global Catalog, open Active Directory Sites and Services from the Administrative Tools container within Control Panel or on the Start Menu. Double-click Sites, then Servers, followed by the name of the new server. Next, right-click "NTDS Settings" and select Properties. On the General tab, check the Global Catalog checkbox. Restart the new Domain Controller for changes to take effect.
Since you intend on removing the old Domain Controller from the domain, you need to transfer all the Operations (FSMO) roles to the new Domain Controller.
The current FSMO role configuration for your network can be found by running the command "netdom query fsmo" at a command prompt on a Domain Controller.
To transfer these FSMO roles to the new domain controller, follow the information detailed in the following Microsoft Support article:
http://support.microsoft.com/kb/324801. Please ensure any other information you follow is information regarding the TRANSFER of FSMO roles. Seizing FSMO roles is an emergency operation which should not be performed during this procedure.
DNS is a critical component of your Active Directory network. The easiest way to install the DNS role onto the new server is to follow the instructions outlined at
http://technet2.microsoft.com/WindowsServer2008/en/library/3cf4d1b1-7a6e-4438-bf4f-22d9468c17321033.mspx You should be already using Active Directory-integrated DNS zones, which is the easiest method of allowing DNS replication to occur - DNS information is stored in Active Directory and replicates with Domain Controller replication traffic. To check if your DNS zones are AD-integrated (and convert them if not), please follow
http://support.microsoft.com/kb/227844.
You probably want to enable DNS forwarding in the DNS console on the server, too. This forwards lookups for external domains to a DNS server at your ISP, which allows the server to effectively resolve DNS for external domains. More information on forwarders can be found at
http://technet2.microsoft.com/WindowsServer/en/Library/ee992253-235e-4fd4-b4da-7e57e70ad3821033.mspx.
To move DHCP to the new server, you will need to first install the role. To install the role in Windows Server 2008, check the DHCP Server role option within the Add Roles wizard in the Server Manager. To correctly configure DHCP after the role is installed on your new server, you will need to ensure you configure it to distribute IP addresses which are in a different range to the IP scope defined on the other DHCP server. You should also ensure the correct DNS and WINS servers are entered into the scope options. Remember that the only DNS servers which should be configured on workstations are the Domain Controllers which are also acting as DNS servers - no ISP DNS server should ever be set through DHCP.
Once all of these steps have been completed, you should have successfully transferred all of the Active Directory roles to the new domain controller. At this stage, I would suggest you shut down the old domain controller and check to ensure all services on workstations and servers are working correctly - including logins. If they are, you should be safe to switch the old DC back on, run dcpromo and demote it from its Domain Controller role. This will remove the DC as a Domain Controller, leaving it as a member server on the network.
To completely remove the DC from the network, you will need to remember that any other data - including folder redirection folders and user profiles - should be replicated or otherwise transferred to either the new server or another location on the network.
-tigermatt
