SHUTDOWN(8) System Manager's Manual SHUTDOWN(8)
shutdown - close down the system at a given time
/etc/shutdown [ -k ] [ -r ] [ -h ] 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, saving
them from system administrators, hackers, and gurus, who would other-
wise 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 sys-
tem down at the time of day indicated (as a 24-hour clock).
At intervals which get closer together as apocalypse approaches, warn-
ing 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 writ-
ing 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 file /usr/adm/shutdownlog,
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 time of the shutdown and the warning message are placed in
/etc/nologin and should be used to inform the users about when the sys-
tem will be back up and why it is going down (or anything else).
/etc/nologin tells login not to let anyone log in
/usr/adm/shutdownlog log file for successful shutdowns.
Only allows you to kill the system between now and 23:59 if you use the
absolute time for shutdown.
4th Berkeley Distribution 1 April 1981 SHUTDOWN(8)