• SSH into the OS or use Terminal
  • Type date (time will be displayed as 17:30
  • Type sudo at 18:00 (this schedules the next command to run in 30 min from 17:30)
  • Type your password
  • Type shutdown -r now and press Enter (other commands typed will now be scheduled at 18:00, just a reboot is required for now)
  • Press CRTL+D

You'll see your task scheduled. You may want to use this when you are running updates on a system and want to automatically reboot.  To be on the safe side you will want to schedule the reboot well after updates have had time to run.