Specifications

Chapter 6 Accessing Apple Hardware from the Command Line 43
Parameter Description
seconds The number of seconds before the computer
starts after a power failure. This value must be
a multiple of 30.
Changing a Remote Computer’s Startup Disk
You can change a remote computer’s startup disk using SSH.
To determine available startup volumes:
Log in to the remote computer using SSH, and enter:
systemsetup -liststartupdisks
To change the startup disk:
Log in to the remote computer using SSH, and enter:
CodeLinesystemsetup -setstartupdisks /Volumes/SnowLeopardServerHD/System/
Library/CoreServices
For information about using SSH to log in to a remote computer, see “SSH” on page 27.
Shutting Down a Computer
To shut down a computer at a specic 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
Parameter Description
computer The IP address or DNS name of the computer
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 o 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.