You have many Domain Controllers, and you want to prepare for quick replacement in case of a complete failure.
You are using the DCPROMO unattended option "AllowDomainControllerReinstall=1", so the promotion re-uses existing AD objects during the promotion.
You find that the promotion fails. In the DCPROMOUI.LOG you find:
dcpromoui 5C8.BA0 075E 12:02:29.856 OperationStatus : 0x4E2 !0 => error
dcpromoui 5C8.BA0 075F 12:02:29.856 DisplayString : Active Directory Domain Services could not determine if this directory server name CN=NTDS Settings,CN=DC2,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=contoso,DC=com is unique on the remote directory server DC1.contoso.com. If this name is not unique, rename this directory server.
The error is ERROR_DOMAIN_CONTROLLER_EXISTS.
Only after this it reads the option from the answer file:
dcpromoui 5C8.BA0 0780 12:02:31.200 Enter GetAnswerFileOption AllowDomainControllerReinstall
dcpromoui 5C8.BA0 0781 12:02:31.200 Enter AnswerFile::GetOption AllowDomainControllerReinstall
dcpromoui 5C8.BA0 0782 12:02:31.200 using value from cmdline
dcpromoui 5C8.BA0 0783 12:02:31.200 Yes
dcpromoui 5C8.BA0 0784 12:02:31.200 Enter State::SetDomainControllerReinstallFlag true
Currently there are two issues:
- Even though the domain join appears to work correctly, it would cause a problem later in promotion.
- The parameter "AllowDomainControllerReinstall" is not read properly during startup of DCPROMO.
To work around the issue, delete the Computer Account of the Domain Controller to be reinstalled, using Active Directory Users and Computers. In Windows Server 2008 R2, this will also clean out the NTDS Settings object of the DC.