path: root/static/freebsd/man8/reboot.8

.\" Copyright (c) 1990, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.Dd December 8, 2025
.Dt REBOOT 8
.Os
.Sh NAME
.Nm reboot ,
.Nm halt ,
.Nm fastboot ,
.Nm fasthalt
.Nd stopping and restarting the system
.Sh SYNOPSIS
.Nm halt
.Op Fl DflNnpq
.Op Fl e Ar variable=value
.Op Fl k Ar kernel
.Op Fl o Ar options
.Nm
.Op Fl cDdflNnpqr
.Op Fl e Ar variable=value
.Op Fl k Ar kernel
.Op Fl o Ar options
.Nm fasthalt
.Op Fl DflNnpq
.Op Fl e Ar variable=value
.Op Fl k Ar kernel
.Op Fl o Ar options
.Nm fastboot
.Op Fl dDflNnpq
.Op Fl e Ar variable=value
.Op Fl k Ar kernel
.Op Fl o Ar options
.Sh DESCRIPTION
The
.Nm halt
and
.Nm
utilities stop and restart the system, respectively.
.Pp
Both utilities have two distinct modes of operation.
In normal mode, they send a signal to the
.Xr init 8
process, which shuts down running services and stops or restarts the
system.
In fast mode, they flush the file system cache to disk, send all
running processes a
.Dv SIGTERM
(and subsequently a
.Dv SIGKILL )
and stop or restart the system themselves.
Services are killed, not shut down, which may result in data loss.
.Pp
In either mode, the action is logged, including entering a shutdown
record into the user accounting database.
.Pp
The following options are available:
.Bl -tag -width indent
.It Fl c
The system will turn off the power and then turn it back on if it can.
If the power down action fails, the system
will halt or reboot normally, depending on whether
.Nm halt
or
.Nm
was called.
At the present time, only the
.Xr ipmi 4
driver implements the power cycle functionality and only on hardware
with a BMC that supports power cycling.
Unlike power off, the amount of hardware that supports power cycling
is small.
.It Fl D
Delete existing
.Nm nextboot
configuration and exit.
.It Fl d
The system is requested to create a crash dump.
This option is
supported only when rebooting, and it has no effect unless a dump
device has previously been specified with
.Xr dumpon 8 .
.It Fl e Ar variable=value
Sets
.Va variable
to
.Va value
in the loader's and kernel's environment.
If
.Va value
is not already enclosed in double quotes, they will be added before writing to the
.Nm nextboot
configuration.
Care should be taken if
.Va value
contains any characters that are special to the shell or loader's configuration
parsing code.
.It Fl f
Forced mode.
Normally,
.Nm halt
or
.Nm
checks for the presence of the next kernel,
and absence of the
.Pa /var/run/noshutdown
file.
Without this flag, the operation is rejected if one of these checks
fails.
.It Fl k Ar kname
Boot the specified kernel
.Ar kname
on the next system boot.
This is a one-shot option, the
.Em default
kernel will be booted on successive boots.
No
.Nm reboot
or
.Nm halt
will be performed if
.Em /boot/kname/kernel
does not exist unless the
.Fl f
flag is specified.
.It Fl l
The halt or reboot is
.Em not
logged to the system log.
This option is intended for applications such as
.Xr shutdown 8 ,
that call
.Nm
or
.Nm halt
and log this themselves.
.It Fl N
The file system cache is not flushed during the initial process clean-up,
however the kernel level
.Xr reboot 2
is still processed with a sync.
This option can be useful for performing a
.Dq best-effort
reboot when devices might be unavailable.
This can happen when devices have been disconnected, such as with
.Xr iscsi 4 .
.It Fl n
The file system cache is not flushed.
This option should probably not be used.
.It Fl o Ar options
This option
allows the passing of kernel flags for the next boot.
.It Fl p
The system will turn off the power if it can.
If the power down action fails, the system
will halt or reboot normally, depending on whether
.Nm halt
or
.Nm
was called.
.It Fl q
The system is halted or restarted quickly and ungracefully, and only
the flushing of the file system cache is performed (if the
.Fl n
option is not specified).
This option should probably not be used.
.It Fl r
The system kills all processes, unmounts all filesystems, mounts the new
root filesystem, and begins the usual startup sequence.
After changing vfs.root.mountfrom with
.Xr kenv 1 ,
.Nm Fl r
can be used to change the root filesystem while preserving kernel state.
This requires the
.Xr tmpfs 4
kernel module to be loaded because
.Xr init 8
needs a place to store itself after the old root is unmounted, but
before the new root is in place.
.El
.Pp
The
.Nm fasthalt
and
.Nm fastboot
utilities invoke
.Nm halt
and
.Nm ,
respectively, in fast mode.
.Pp
The
.Xr shutdown 8
utility can be used to not only stop or restart the system right away,
but also schedule a stop or restart in the future, and will, unlike
.Nm halt
and
.Nm ,
give users advance warning of their impending doom.
.Sh EXAMPLES
Replace current root filesystem with UFS mounted from
.Pa /dev/ada0s1a :
.Bd -literal -offset indent
kenv vfs.root.mountfrom=ufs:/dev/ada0s1a
reboot -r
.Ed
.Pp
This mechanism can also be used with NFS, with a caveat that
it only works with NFSv4, and requires a numeric IPv4 address:
.Bd -literal -offset indent
kenv vfs.root.mountfrom=nfs:192.168.1.1:/share/name
reboot -r
.Ed
.Sh SEE ALSO
.Xr kenv 1 ,
.Xr reboot 2 ,
.Xr getutxent 3 ,
.Xr ipmi 4 ,
.Xr boot 8 ,
.Xr dumpon 8 ,
.Xr nextboot 8 ,
.Xr savecore 8 ,
.Xr shutdown 8 ,
.Xr sync 8
.Sh HISTORY
A
.Nm
utility appeared in
.Bx 4.0 .
.Pp
Historically, the
.Xr shutdown 8
utility was used when the system needed to be halted or restarted
cleanly in the normal course of operations, and the
.Nm halt
and
.Nm
utilities were blunt instruments used only in single-user mode or if
exceptional circumstances made a normal shutdown impractical.
As other operating systems did away with this distinction, and it
became clear that many users were unaware of it and were using
.Nm
in the belief that it performed a clean shutdown, it was rewritten to
conform to that expectation.