SHUTDOWN(8)

NAME
shutdown - close down the system at a given time

SYNOPSIS
/usr/sbin/shutdown [ -fhknr ] time [ warning-message ... ]

DESCRIPTION
Shutdown provides an automated shutdown procedure which a super-user can use to notify users nicely when the system is shutting down, saving them from system administrators, hackers, and gurus, who would otherwise not bother with niceties.

Time is the time at which shutdown will bring the system down and may be the word now (indicating an immediate shutdown) or specify a future time in one of two formats: +number and hour:min. The first form brings the system down in number minutes and the second brings the system down at the time of day indicated (as a 24-hour clock).

At intervals which get closer together as apocalypse approaches, warning messages are displayed at the terminals of all users on the system. Five minutes before shutdown, or immediately if shutdown is in less than 5 minutes, logins are disabled by creating /etc/nologin and writing a message there. If this file exists when a user attempts to log in, login(1) prints its contents and exits. The file is removed just before shutdown exits.

At shutdown time a message is written to the system log daemon, syslogd(8), containing the time of shutdown, who ran shutdown and the reason. Then a terminate signal is sent at init to bring the system down to single-user state. Alternatively, if -r, -h, or -k was used, then shutdown will exec reboot(8), halt(8), or avoid shutting the system down (respectively). (If it isn't obvious, -k is to make people think the system is going down!) The -n option can be used with -h or -r to prevent reboot(8) or halt(8) performing a sync(2) prior to the system stopping. The -f option causes a fast recovery (ie no automatic fsck(8) of the discs) when the system restarts.

The time of the shutdown and the warning message are placed in /etc/nologin and should be used to inform the users about when the system will be back up and why it is going down (or anything else).

FILES
/etc/nologin    tells login not to let anyone log in

SEE ALSO
login(1), reboot(8), syslogd(8)

BUGS
Only allows you to kill the system between now and 23:59 if you use the absolute time for shutdown.