system_cmds-336.20.tar.gz

[apple/system_cmds.git] / shutdown.tproj / shutdown.8

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.\"     @(#)shutdown.8	8.2 (Berkeley) 4/27/95
.\" $FreeBSD: src/sbin/shutdown/shutdown.8,v 1.21 2002/12/23 16:04:50 ru Exp $
.\"
.Dd December 11, 1998
.Dt SHUTDOWN 8
.Os
.Sh NAME
.Nm shutdown
.Nd "close down the system at a given time"
.Sh SYNOPSIS
.Nm
.Op Fl
.Oo
.Fl h 
.Op Fl u
|
.Fl r | Fl k
.Oc
.Oo
.Fl o
.Op Fl n
.Oc
.Ar time
.Op Ar warning-message ...
.Sh DESCRIPTION
The
.Nm
utility provides an automated shutdown procedure for super-users
to nicely notify users when the system is shutting down,
saving them from system administrators, hackers, and gurus, who
would otherwise not bother with such niceties.
.Pp
The following options are available:
.Bl -tag -width indent
.It Fl h
The system is halted at the specified
.Ar time .
.It Fl r
The system is rebooted at the specified
.Ar time .
.It Fl k
Kick everybody off.
The
.Fl k
option
does not actually halt the system, but leaves the
system multi-user with logins disabled (for all but super-user).
.It Fl o
If 
.Fl h
or
.Fl r
is specified,
.Nm
will execute
.Xr halt 8
or
.Xr reboot 8
instead of sending signal to
.Xr init 8 .
.It Fl n
If the
.Fl o
is specified, prevent the file system cache from being flushed by passing
.Fl n
option to
.Xr halt 8
or
.Xr reboot 8 .
This option should probably not be used.
.It Fl u
The system is halted up until the point of removing system power, but waits 
before removing power for 5 minutes so that an external UPS 
(uninterruptible power supply) can forcibly remove power. 
This simulates a dirty shutdown to permit a later automatic power on. OS X uses
this mode automatically with supported UPSs in emergency shutdowns.
.It Ar time
.Ar Time
is the time at which
.Nm
will bring the system down and
may be the word
.Ar now
(indicating an immediate shutdown) or
specify a future time in one of two formats:
.Ar +number ,
or
.Ar yymmddhhmm ,
where the year, month, and day may be defaulted
to the current system values.  The first form brings the system down in
.Ar number
minutes and the second at the absolute time specified.
.It Ar warning-message
Any other arguments comprise the warning message that is broadcast
to users currently logged into the system.
.It Fl
If
.Sq Fl
is supplied as an option, the warning message is read from the standard
input.
.El
.Pp
At intervals, becoming more frequent as apocalypse approaches
and starting at ten hours before shutdown, warning messages are displayed
on the terminals of all users logged in.  Five minutes before
shutdown, or immediately if shutdown is in less than 5 minutes,
logins are disabled by creating
.Pa /var/run/nologin
and copying the
warning message there.  If this file exists when a user attempts to
log in,
.Xr login 1
prints its contents and exits.  The file is
removed just before
.Nm
exits.
.Pp
At shutdown time a message is written to the system log, containing the
time of shutdown, the person who initiated the shutdown and the reason.
Corresponding signal is then sent to
.Xr init 8
to respectively halt, reboot or bring the system down to single-user state
(depending on the above options).
The time of the shutdown and the warning message
are placed in
.Pa /var/run/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).
.Pp
A scheduled shutdown can be canceled by killing the
.Nm
process (a
.Dv SIGTERM
should suffice).
The
.Pa /var/run/nologin
file that
.Nm
created will be removed automatically.
.Sh FILES
.Bl -tag -width /var/run/nologin -compact
.It Pa /var/run/nologin
tells login not to let anyone log in
.El
.Sh SEE ALSO
.Xr kill 1 ,
.Xr login 1 ,
.Xr wall 1 ,
.Xr nologin 5 ,
.Xr halt 8 ,
.Xr init 8 ,
.Xr reboot 8
.Sh BACKWARD COMPATIBILITY
The hours and minutes in the second time format may be separated by
a colon (``:'') for backward compatibility.
.Sh HISTORY
The
.Nm
utility appeared in
.Bx 4.0 .