Change / Set Administrator Password
If your machine is configured as a Domain Master, then you will need an administrative user defined who can authorize new machines to logon to the domain. This is where you set the password for that user.

The username is root.

This option will show up as "Set Administrator Password" if you do not currently have an administrative password set. If you already have one set and you wish to change it, this option will show up as "Change Administrator Password."