SHUTDOWN(8) System Manager's Manual SHUTDOWN(8)
shutdown - close down the system at a given time
shutdown [ -k ] [ -r ] [ -h ] [ -f ] [ -n ] time [ warning-message ... ]
Shutdown provides an automated shutdown procedure which a super-user can use to notify users nicely when the system is shutting down, sav-
ing 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 sys-
tem. 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 in the system log, containing the time of shutdown, who ran shutdown and the reason. Then a termi-
nate signal is sent to 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
With the -f option, shutdown arranges, in the manner of fastboot(8), that when the system is rebooted the file systems will not be checked.
The -n option prevents the normal sync(2) before stopping.
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).
/etc/nologin tells login not to let anyone log in
login(1), reboot(8), fastboot(8)
Only allows you to kill the system between now and 23:59 if you use the absolute time for shutdown.
4th Berkeley Distribution November 16, 1996 SHUTDOWN(8)