NetBoot service item is dimmed in Server Admin 10.4 and can‘t be administered

Issue or symptom

The Netboot or other service list items in Server Admin Computers & Services column may be dimmed ("grayed out"). Dimmed items cannot be administered in Server Admin.

Solution

1. On the affected server, quit Server Admin.
2. Delete the /var/servermgrd/ directory.
3. In Terminal, execute this command:
   
   sudo launchctl stop com.apple.servermgrd
   
4. Restart Server Admin.