system_cmds-671.10.3.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 shutdown
.Op Fl
.Oo
.Fl h 
.Op Fl u
|
.Fl r | Fl s | Fl k
.Oc
.Oo
.Fl o
.Op Fl n
.Oc
.Ar time
.Op Ar warning-message ...
.Sh DESCRIPTION
The
.Nm shutdown
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 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 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 o
If
.Fl h
or
.Fl r
is specified,
.Nm shutdown
will execute
.Xr halt 8
or
.Xr reboot 8
instead of sending a signal to
.Xr launchd 8 .
.It Fl r
The system is rebooted at the specified
.Ar time .
.It Fl s
The system is put to sleep at the specified
.Ar time .
.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 shutdown
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.
.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 launchd 8
to respectively halt, reboot or bring the system down to single-user state
(depending on the above options).
.Pp
A scheduled shutdown can be canceled by killing the
.Nm shutdown
process (a
.Dv SIGTERM
should suffice).
.Sh SIGTERM TO SIGKILL INTERVAL
Upon shutdown, all running processes are sent a SIGTERM followed by a SIGKILL.
The
.Dv SIGKILL
will follow the
.Dv SIGTERM
by an intentionally indeterminate period of time.
Programs are expected to take only enough time to flush all dirty data and exit.
Developers are encouraged to file a bug with the OS vendor, should they encounter an issue with this functionality.
.Sh SEE ALSO
.Xr kill 1 ,
.Xr login 1 ,
.Xr wall 1 ,
.Xr halt 8 ,
.Xr launchd 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 shutdown
utility appeared in
.Bx 4.0 .