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@(#)shutdown.8 6.5 (Berkeley) 09/18/88

C 4 shutdown - close down the system at a given time /etc/shutdown [ -fhkrn ] 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 otherwise not bother with such 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, or yymmddhhmm, where the year, month, and day may be defaulted to the current system values. The first form brings the system down in number minutes and the second at the absolute time specified.

Any other arguments comprise the warning message that is broadcast to users currently logged into the system; if no other arguments are provided, the warning message is read from the standard input.

At intervals, which get closer together as apocalypse approaches, starting at ten hours before shutdown, 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 copying the warning 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 terminate signal is sent to init to bring the system down to single-user state. Alternatively, if -r, -h, or -k is 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!)

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).

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

15 /fastboot tells /etc/rc not to run fsck when rebooting

login(1), wall(1), fastboot(8), halt(8), reboot(8) The hours and minutes in the second time format may be separated by a colon (``:'') for backward compatibility.