Promote 2008 Server Core to a Domain Controller

To promote the server to be a DC in your domain, enter the following command:

Dcpromo /unattend /replicaOrnewDomain:replica
/replicaDomainDNSName:mydomain.local /ConfirmGC:yes
/username:mydomain\administrator /Password:*
/safeModeAdminPassword:LetmeIn123

This will run dcpromo adding the server as a global catalog server to the mydomain.local domain. The Domain restore Mode password will be set to LetMeIn123. You will be asked to enter the domain administrator password when the command is run (by way of the /password:* command)

Allow the process to complete.  Once it does the server will automatically reboot and will be a domain controller.