working simple-minded (n^2 alg) tree version.

[unix-history] / usr / src / sbin / shutdown / shutdown.8

.\" Copyright (c) 1980 Regents of the University of California.
.\" All rights reserved.  The Berkeley software License Agreement
.\" specifies the terms and conditions for redistribution.
.\"
.\"	@(#)shutdown.8	6.5 (Berkeley) %G%
.\"
.TH SHUTDOWN 8 ""
.UC 4
.SH NAME
shutdown \- close down the system at a given time
.SH SYNOPSIS
.B /etc/shutdown
[
.B \-fhkrn
]
time [ warning-message ... ]
.SH DESCRIPTION
.I 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.
.PP
.I Time
is the time at which \fIshutdown\fP will bring the system down and
may be the word \fInow\fP (indicating an immediate shutdown) or
specify a future time in one of two formats: \fI+number\fP, or
\fIyymmddhhmm\fP, where the year, month, and day may be defaulted
to the current system values.  The first form brings the system down in
\fInumber\fP minutes and the second at the absolute time specified.
.PP
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.
.PP
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 \fI/etc/nologin\fP and copying the
warning message there.  If this file exists when a user attempts to
log in, \fIlogin\fP(1) prints its contents and exits.  The file is
removed just before \fIshutdown\fP exits.
.PP
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 \fIinit\fP to bring the system down to single-user state.
Alternatively, if
.B \-r,
.B \-h,
or
.B \-k
is used, then
.I shutdown
will exec
.IR reboot (8),
.IR halt (8),
or avoid shutting the system down (respectively).
(If it isn't obvious,
.B \-k
is to make people
.I think
the system is going down!)
.PP
With the
.B \-f
option,
.I shutdown
arranges, in the manner of
.IR fastboot (8),
that when the system is rebooted the file systems will not
be checked.  The
.B \-n
option prevents the normal
.IR sync (2)
before stopping.
.PP
The time of the shutdown and the warning message
are placed in \fI/etc/nologin\fP 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).
.SH FILES
.TP 15
/etc/nologin
tells login not to let anyone log in
.TP 15
/fastboot
tells /etc/rc not to run fsck when rebooting
.SH "SEE ALSO"
login(1), wall(1), fastboot(8), halt(8), reboot(8)
.SH "BACKWARD COMPATIBILITY"
The hours and minutes in the second time format may be separated by
a colon (``:'') for backward compatibility.