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.\"     @(#)shutdown.8	8.1 (Berkeley) 6/5/93
.\"
.Dd June 5, 1993
.Dt SHUTDOWN 8
.Os BSD 4
.Sh NAME
.Nm shutdown
.Nd "close down the system at a given time"
.Sh SYNOPSIS
.Nm shutdown
.Op Fl 
.Op Fl hkrnx
.Ar time
.Op Ar warning-message ...
.Sh DESCRIPTION
.Nm Shutdown
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
Available friendlinesses:
.Bl -tag -width time
.It Fl h
The system is halted at the specified
.Ar time
when
.Nm shutdown
execs
.Xr halt 8 .
.It Fl k
Kick every body 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
Prevent the normal
.Xr sync 2
before stopping.
.It Fl r 
.Nm Shutdown
execs
.Xr reboot 8
at the specified
.Ar time .
.It Fl x
Halt the system at the specified
.Ar time
and turn off the power supply.
This option can be used when power-control supported.
.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
.Ql 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 /etc/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 shutdown
exits.
.Pp
At shutdown time a message is written in the system log, containing the
time of shutdown, who initiated the shutdown and the reason.
A terminate
signal is then sent to
.Xr init
to bring the system down to single-user state (depending on above
options).
The time of the shutdown and the warning message
are placed in
.Pa /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).
.Sh FILES
.Bl -tag -width /etc/nologin -compact
.It Pa /etc/nologin
tells login not to let anyone log in
.El
.Sh SEE ALSO
.Xr login 1 ,
.Xr wall 1 ,
.Xr nologin 5 ,
.Xr halt 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
command appeared in
.Bx 4.0 .