Specifications

56 Chapter 4 Restarting or Shutting Down a Computer
Changing a Remote Computer’s Startup Disk
You can change a remote computer’s startup disk using SSH.
To change the startup disk:
Log in to the remote computer using SSH and enter:
$ bless -folder "/Volumes/
disk /System/Library/CoreServices" -setBoot
For information about using SSH to log in to a remote computer, see “Sending
Commands to a Remote Computer” on page 28.
Shutting Down a Computer
To shut down a computer at a specific time, use the shutdown tool. For more
information, see the shutdown man page.
To shut down a remote computer immediately:
$ ssh -l root computer shutdown -h now
To shut down the local computer in 30 minutes:
$ shutdown -h +30
Shutting Down While Leaving the Computer on and Powered
To support UPS restart after power failure, the shutdown tool provides the -u option.
This option halts system shutdown before the shutdown tool instructs the power
manager to turn off the power supply.
The -u option keeps the system halted and waits for 5 minutes before removing power
so an external UPS can forcibly remove power.
Using the -u option simulates a dirty shutdown, which allows a later automatic power
on. The operating system uses the -u option with supported UPS devices in emergency
shutdowns.
Parameter Description
disk The name of the disk that contains the startup volume
Parameter Description
computer The IP address or DNS name of the computer