Using Ntdsutil.exe to transfer FSMO roles to a domain controller

When you are going to migrate AD to new machine, you must need to transfer FSMO role to become new server as primary.
so that u can demote old server from AD forest.

See below how to transfer FSMO roles using ntdsutil.

Transfer FSMO roles

To transfer the FSMO roles by using the Ntdsutil utility, follow these steps:

1. Log on to a Windows 2000 Server-based or Windows Server 2003-based member computer or domain controller that is located in the forest where FSMO roles are being transferred. We recommend that you log on to the domain controller that you are assigning FSMO roles to. The logged-on user should be a member of the Enterprise Administrators group to transfer Schema master or Domain naming master roles, or a member of the Domain Administrators group of the domain where the PDC emulator, RID master and the Infrastructure master roles are being transferred.

2. Click Start, click Run, type ntdsutil in the Open box, and then click OK.

3. Type roles, and then press ENTER.
Note To see a list of available commands at any one of the prompts in the Ntdsutil utility, type ?, and then press ENTER.

4. Type connections, and then press ENTER.

5. Type connect to server servername, and then press ENTER, where servername is the name of the domain controller you want to assign the FSMO role to.

6. At the server connections prompt, type q, and then press ENTER.
7. Type transfer role, where role is the role that you want to transfer. For a list of roles that you can transfer, type ? at the fsmo maintenance prompt, and then press ENTER, or see the list of roles at the start of this article. For example, to transfer the RID master role, type transfer rid master. The one exception is for the PDC emulator role, whose syntax is transfer pdc, not transfer pdc emulator.

8. At the fsmo maintenance prompt, type q, and then press ENTER to gain access to the ntdsutil prompt. Type q, and then press ENTER to quit the Ntdsutil utility.