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.\"	@(#)reboot.8	8.1 (Berkeley) 6/9/93
.\"
.Dd September 12, 2016
.Dt REBOOT 8
.Os
.Sh NAME
.Nm reboot ,
.Nm poweroff ,
.Nm halt
.Nd restarting, powering down and stopping the system
.Sh SYNOPSIS
.Nm halt
.Op Fl dlnpqvxz
.Nm poweroff
.Op Fl dlnqvxz
.Nm
.Op Fl dlnqvxz
.Op Ar arg ...
.Sh DESCRIPTION
The
.Nm poweroff ,
.Nm halt
and
.Nm
utilities flush the file system cache to disk, send all running processes
a
.Dv SIGTERM ,
wait for up to 30 seconds for them to die, send a
.Dv SIGKILL
to the survivors and, respectively, power down, halt or restart the system.
The action is logged, including entering a shutdown record into the login
accounting file and sending a message via
.Xr syslog 3 .
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl d
Create a dump before halting or restarting.
This option is useful for debugging system dump procedures or
capturing the state of a corrupted or misbehaving system.
.It Fl l
Suppress sending a message via
.Xr syslog 3
before halting or restarting.
.It Fl n
Do not flush the file system cache.
This option should be used with extreme caution.
It can be used if a disk or a processor is on fire.
.It Fl p
Attempt to powerdown the system.
If the powerdown fails, or the system does not support
software powerdown, the system will halt.
This option is only valid for
.Nm halt .
.It Fl v
To enable verbose messages on the console, pass the
.Xr boothowto 9
flag
.Dv AB_VERBOSE
to
.Xr reboot 2 .
.It Fl x
To enable debugging messages on the console, pass the
.Xr boothowto 9
flag
.Dv AB_DEBUG
to
.Xr reboot 2 .
.It Fl z
To silence some shutdown messages on the console, pass the
.Xr boothowto 9
flag
.Dv AB_SILENT
to
.Xr reboot 2 .
.It Fl q
Do not give processes a chance to shut down before halting or restarting.
This option should not normally be used.
.El
.Pp
If there are any arguments passed to
.Nm reboot
they are concatenated with spaces and passed as
.Fa bootstr
to the
.Xr reboot 2
system call.
The string is passed to the firmware on platforms that support it.
.Pp
Normally, the
.Xr shutdown 8
utility is used when the system needs to be halted or restarted, giving
users advance warning of their impending doom.
.Sh SEE ALSO
.Xr reboot 2 ,
.Xr syslog 3 ,
.Xr utmp 5 ,
.Xr boot 8 ,
.Xr init 8 ,
.Xr rescue 8 ,
.Xr shutdown 8 ,
.Xr sync 8
.Sh HISTORY
A
.Nm
command appeared in
.Bx 4.0 .
.Pp
The
.Nm poweroff
command first appeared in
.Nx 1.5 .
.Sh CAVEATS
Once the command has begun its work, stopping it before it completes
will probably result in a system so crippled it must be
physically reset.
To prevent premature termination, the command
blocks many signals early in its execution.
However, nothing can defend against deliberate attempts to evade this.
.Pp
This command will stop the system without running any
.Xr shutdown 8
scripts.
Amongst other things, this means that swapping will not be
disabled so that
.Xr raid 4
can shutdown cleanly.
You should normally use
.Xr shutdown 8
unless you are running in single user mode.
.Sh BUGS
The single user shell will ignore the
.Dv SIGTERM
signal.
To avoid waiting for the timeout when
rebooting or halting from the single user shell, you have to
.Ic exec reboot
or
.Ic exec halt .