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.Dd August 4, 2024
.Dt SHUTDOWN 8
.Os
.Sh NAME
.Nm shutdown ,
.Nm poweroff
.Nd "close down the system at a given time"
.Sh SYNOPSIS
.Nm
.Op Fl
.Oo
.Fl c | Fl h | Fl p |
.Fl r | Fl k
.Oc
.Oo
.Fl o
.Op Fl n
.Oc
.Op Fl q
.Ar time
.Op Ar warning-message ...
.Nm poweroff
.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.
In order to use the
.Nm
command, the user must have root privileges or be a member of the
operator group.
.Pp
The following options are available:
.Bl -tag -width indent
.It Fl c
The system is power cycled (power turned off and then back on)
at the specified time.
If the hardware doesn't support power cycle, the system will be
rebooted.
At the present time, only systems with BMC supported by the
.Xr ipmi 4
driver that implement this functionality support this flag.
The amount of time the system is off is dependent on the device
that implements this feature.
.It Fl h
The system is halted at the specified
.Ar time .
.It Fl p
The system is halted and the power is turned off
(hardware support required, otherwise 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 one of the
.Fl c ,
.Fl h ,
.Fl p
or
.Fl r
options are specified,
.Nm
will execute
.Xr halt 8
or
.Xr reboot 8
instead of sending a signal to
.Xr init 8 .
.It Fl n
If the
.Fl o
option is specified, prevent the file system cache from being flushed by passing
.Fl n
to
.Xr halt 8
or
.Xr reboot 8 .
This option should probably not be used.
.It Fl q
Shut down quietly.
Suppress the warning message to all logged in users about system shutdown.
It is an error to supply a
.Ar warning-message
when warnings are suppressed.
.It Ar time
.Ar Time
is the time at which
.Nm
will bring the system down and
may be the case-insensitive word
.Ar now
(indicating an immediate shutdown) or
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.
.Ar +number
may be specified in units other than minutes by appending the corresponding
suffix:
.Dq Li s ,
.Dq Li sec ,
.Dq Li m ,
.Dq Li min ,
.Dq Li h ,
.Dq Li hour .
.Pp
If an absolute time is specified, but not a date,
and that time today has already passed,
.Nm
will assume that the same time tomorrow was meant.
(If a complete date is specified which has already passed,
.Nm
will print an error and exit without shutting the system down.)
.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.
The 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.
.Pp
When run without options, the
.Nm
utility will place the system into single user mode at the
.Ar time
specified.
.Pp
Calling
.Dq Nm poweroff
is equivalent to running:
.Bd -literal -offset indent
shutdown -p now
.Ed
.Sh FILES
.Bl -tag -width /var/run/nologin -compact
.It Pa /var/run/nologin
tells
.Xr login 1
not to let anyone log in
.El
.Sh EXAMPLES
Reboot the system in 30 minutes and display a warning message on the terminals
of all users currently logged in:
.Pp
.Dl # shutdown -r +30 \&"System will reboot\&"
.Sh COMPATIBILITY
The hours and minutes in the second time format may be separated by
a colon (``:'') for backward compatibility.
.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 HISTORY
A
.Nm
command was originally written by Ian Johnstone for UNSW's modified
.At "6th Edn" .
It was modified and then incorporated in
.Bx 4.1 .