libc/sys/reboot.2

.\"	$OpenBSD: reboot.2,v 1.16 2014/01/21 03:15:45 schwarze Exp $
.\"	$NetBSD: reboot.2,v 1.5 1995/02/27 12:36:02 cgd Exp $
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.\"     @(#)reboot.2	8.1 (Berkeley) 6/4/93
.\"
.Dd $Mdocdate: January 21 2014 $
.Dt REBOOT 2
.Os
.Sh NAME
.Nm reboot
.Nd reboot system or halt processor
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Fd #include <sys/reboot.h>
.Ft int
.Fn reboot "int howto"
.Sh DESCRIPTION
.Fn reboot
reboots the system.
Only the superuser may reboot a machine on demand.
However, a reboot is invoked
automatically in the event of unrecoverable system failures.
.Pp
.Fa howto
is a mask of options; the system call interface allows the following
options, defined in the include file
.In sys/reboot.h ,
to be passed
to the new kernel or the new bootstrap and init programs.
.Bl -tag -width RB_INITNAMEA
.It Dv RB_AUTOBOOT
The default, causing the system to reboot in its usual fashion.
.It Dv RB_ASKNAME
Interpreted by the bootstrap program itself, causing it to
prompt on the console as to what file should be booted.
Normally, the system is booted from the file
.Dq Em xx Ns (0,0)bsd ,
where
.Em xx
is the default disk name,
without prompting for the file name.
.It Dv RB_DFLTROOT
Use the compiled in root device.
Normally, the system uses the device from which it was booted
as the root device if possible.
(The default behavior is dependent on the ability of the bootstrap program
to determine the drive from which it was loaded, which is not possible
on all systems.)
.It Dv RB_DUMP
Dump kernel memory before rebooting; see
.Xr savecore 8
for more information.
.It Dv RB_HALT
The processor is simply halted; no reboot takes place.
.It Dv RB_POWERDOWN
If used in conjunction with
.Dv RB_HALT ,
and if the system hardware supports the function, the system will be
powered off.
.It Dv RB_USERREQ
By default, the system will halt if
.Fn reboot
is called during startup (before the system has finished autoconfiguration),
even if
.Dv RB_HALT
is not specified.
This is because
.Xr panic 9 Ns s
during startup will probably just repeat on the next boot.
Use of this option implies that the user has requested the action
specified (for example, using the
.Xr ddb 4
.Ic boot reboot
command),
so the system will reboot if a halt is not explicitly requested.
.It Dv RB_INITNAME
An option allowing the specification of an init program (see
.Xr init 8 )
other than
.Pa /sbin/init
to be run when the system reboots.
This switch is not currently available.
.It Dv RB_KDB
Load the symbol table and enable a built-in debugger in the system.
This option will have no useful function if the kernel is not configured
for debugging.
Several other options have different meaning if combined
with this option, although their use may not be possible via the
.Fn reboot
call.
See
.Xr ddb 4
for more information.
.It Dv RB_NOSYNC
Normally, the disks are sync'd (see
.Xr sync 8 )
before the processor is halted or rebooted.
This option may be useful if file system changes have been made manually
or if the processor is on fire.
.It Dv RB_RDONLY
Initially mount the root file system read-only.
This is currently the default, and this option has been deprecated.
.It Dv RB_SINGLE
Normally, the reboot procedure involves an automatic disk consistency
check and then multi-user operations.
.Dv RB_SINGLE
prevents this, booting the system with a single-user shell
on the console.
.Dv RB_SINGLE
is actually interpreted by the
.Xr init 8
program in the newly booted system.
.Pp
When no options are given (i.e.,
.Dv RB_AUTOBOOT
is used), the system is
rebooted from file ``bsd'' in the root file system of unit 0
of a disk chosen in a processor specific way.
An automatic consistency check of the disks is normally performed
(see
.Xr fsck 8 ) .
.El
.Sh RETURN VALUES
If successful, this call never returns.
Otherwise, a \-1 is returned and an error is returned in the global
variable
.Va errno .
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er EPERM
The caller is not the superuser.
.El
.Sh SEE ALSO
.Xr ddb 4 ,
.Xr crash 8 ,
.Xr halt 8 ,
.Xr init 8 ,
.Xr reboot 8 ,
.Xr savecore 8 ,
.Xr boot 9 ,
.Xr panic 9
.Sh HISTORY
The
.Fn reboot
system call finally appeared in
.Bx 4.0 .
.Sh BUGS
Not all platforms support all possible arguments.