.Dd October 14, 2024
.Dt SUHTDOWN 8
.Os
.Sh NAME
.Nm shutdown
.Nd shut down the computer
.Sh SYNOPSIS
.Nm
.Op Fl Dhikpr
.Op Ar time
.Op Ar messages ...
.Sh DESCRIPTION
.Nm
gracefully powers off the computer at the specified
.Ar time
by waiting in the background and sending a request to the appropriate
.Xr init 8
process.
.Pp
The system is shut down immediately unless another
.Ar time
is specified:
.Pp
.Bl -tag -width "YYYY-mm-dd HH:MM:SS" -compact
.It Sy now
Shutdown immediately.
.It Sy + Ns Ar minutes Ns Op Ar unit
Shutdown after this many
.Ar minutes .
Optionally another unit can be specified with a
.Sy s ,
.Sy sec ,
.Sy m ,
.Sy min ,
.Sy h ,
or
.Sy hour
suffix.
.It Sy HH:MM
Shutdown at this time today, or tomorrow if in the past.
.It Sy HH:MM:SS
Shutdown at this time today, or tomorrow if in the past.
.It Sy YYYY-mm-dd HH:MM:SS
Shutdown at this time.
.El
.Pp
Countdown messages are broadcast using
.Xr wall 1
with increasing frequency to warn users of the impending shutdown.
Additional
.Ar messages
are included if specified, joined by spaces.
.Pp
Further logins by non-privileged users are prohibited when 5 minutes or less
remain by creating the
.Pa /var/run/nologin
file with the broadcast messages and an explanation.
.Pp
The options are as follows:
.Bl -tag -width "12345678"
.It Fl D
Run in the foreground rather than detaching a child process.
.It Fl h
Halt the operating system.
.It Fl i
Reinitialize the operating system.
.It Fl k
Broadcast the warning messages and create
.Pa nologin
but don't actually shut down.
.It Fl p
Power off the system.
This is the default behavior.
.It Fl r
Reboot the system.
.El
.Sh FILES
.Bl -tag -width "/var/run/nologin"
.It Pa /var/run/nologin
Further non-privileged logins are prohibited if this file exists and users
attempting to log in are shown the contents of this file.
.El
.Sh ASYNCHRONOUS EVENTS
.Bl -tag -width "12345678"
.It Dv SIGINT
Cancels the pending shutdown and deletes the
.Pa nologin
file.
.It Dv SIGTERM
Cancels the pending shutdown and deletes the
.Pa nologin
file.
.It Dv SIGQUIT
Cancels the pending shutdown and deletes the
.Pa nologin
file.
.El
.Sh EXIT STATUS
.Nm
will exit 0 on success and non-zero otherwise.
A child process continues running in the background as it waits for
the scheduled shutdown.
.Pp
The system will always shut down when the time comes if the parent process has
exited successfully even if further errors occur while warning users.
.Sh SEE ALSO
.Xr wall 1 ,
.Xr halt 8 ,
.Xr init 8 ,
.Xr login 8 ,
.Xr poweroff 8 ,
.Xr reboot 8