The domain rename is performed using the Rendom tool, which is installed with Active Directory when running dcpromo. Once this process is started, you must ensure that no changes are made to the forest configuration until complete. The steps are as follows.
1. Run "rendom /list" to generate a state file named Domainlist.xml. This file contains the current forest configuration.
2. Edit the state file, changing the <DNSname> and <NetBiosName> fields to the desired values for the new domain name.
3. Run "rendom /showforest" to show the potential changes; this step does not actually make any changes.
4. Run "rendom /upload" to upload the rename instructions to the configuration directory partition on the domain controller holding the domain naming operations master role. The instructions are then replicated to all other DC's in the forest. Once replicated to all DC's, the rename instructions are ready to be carried out. You can force replication by running the "repadmin /syncall" command.
5. Run "rendom /prepare" to verify the readiness of each domain controller in the forest to carry out the rename instructions. This should contact all DC's successfully and return no errors before proceeding.
6. Run "rendom /execute", this verifies readiness of all DC's, then performs the rename action on each one. There will be a service interruption during this period. Upon completion domain controllers will be rebooted. If an error occurs on a DC during this phase, the entire transaction is rolled back. Any DC's that don't complete successfully after this phase must be demoted and removed from service.
7. Run "gpfixup" to refresh all intradomain references and links to group policy objects.
8. Reboot client computers and member servers twice to obtain new domain name. Because the GUID's of the domain remain the same during the rename process, domain membership is not affected. The DNS suffix of the client machines will also be updated assuming the default option of "Change primary DNS suffix when domain membership changes" is enabled.
9. Run "rendom /clean" to remove references of the old domain name from Active Directory.
10. Run "rendom /end" to unfreeze the forest configuration and allow further changes. This was frozen during the rendom /upload step.
Should you have any problems with clients recognizing the new domain name, you can remove them by running "netdom remove <machine-name> /Domain:<old-domain> /Force", rebooting, and then rejoining the new domain. Once the rename is complete, there is one final change required on domain controllers. The DNS suffix of a DC is not changed as part of this process. This must be changed manually or the DC's will have a DNS suffix that differs from the AD domain name.