shutdown [ -d ] [ -F ] [ -h ] [ -i ] [ -k ] [ -m ] [ -p ] [ -r ] [ -t mmddHHMM [ yy ] ] [ -v ] [ +Time [ Message ] ]
The shutdown command halts the operating system. Only a user with root user authority can run this command. During the default shutdown, users are notified (by a wall command) of the impending system shutdown with a message. However, shutdown is not complete until the user receives a shutdown completion message. Do not attempt to restart the system or turn off the system before the shutdown completion message is displayed; otherwise, file system damage can result.
Note: The halt completed message is not displayed on the tty from which shutdown is invoked if it is connected to the system through a multiport adapter.
As shutdown time approaches, warning messages are displayed on the terminals of all users on the system.
After the specified number of seconds (60 by default), the system stops the accounting and error logging processes and writes an entry to the error log. The shutdown command then runs the killall command to end any remaining processes and runs the sync command to flush all memory resident disk blocks. Finally, it unmounts the file systems and calls the halt command.
Note: Users who have files open on the node that is running the shutdown command, but who are not logged in to that node, are not notified about the shutdown.
If you request a complete halt to the operating system, the shutdown command stops all processes, unmounts all file systems, and calls the halt command.
The system administrator can place local customized shutdown procedures in a shell script named /etc/rc.shutdown. This script runs at the beginning of the shutdown if it exists. If the script runs but fails with a non-zero return code, the shutdown stops.
Attention: If you are bringing the system down to maintenance mode, you must run the shutdown command from the / (root) directory to ensure that it can cleanly unmount the file systems.
Note: By default, if issued on models having a power supply capable of software control, the shutdown command powers down the system.
If the -r flag is specified, the reboot command is run. The -m flag brings the system down to maintenance (single user) mode, and the -k flag avoids shutting down the system. The -i flag runs an interactive shutdown procedure.
To shut down the system quickly, use shutdown -F. This flag bypasses messages to users and brings the system down as quickly as possible. Use this option only if there are no other users logged in.
To schedule the system to restart at a specified future date, use the shutdown -t flag.
| +Time | Specifies the time at which the shutdown command stops the system. An immediate shutdown is indicated by the word now displayed on the screen. A future time can be specified in one of two formats: +number or hour:minute. The first form brings the system down in the specified number of minutes and the second brings the system down at the time of day indicated (as a 24-hour clock). If the Message parameter is specified, the Time parameter must also be specified. |
| Message | Specifies the message |
shutdownThis shuts down the system, waiting 1 minute before stopping the user processes and the init process.
shutdown -m +2This brings the system down from multiuser mode to maintenance mode after waiting 2 minutes.
| /usr/sbin/shutdown | Contains the shutdown command. |
The errpt command, init or telinit command, kill command, killall command, halt command, reboot command, and sync command.
The sigaction subroutine.