1.\" Copyright (c) 1980, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)reboot.2 8.1 (Berkeley) 6/4/93 29.\" $FreeBSD: src/lib/libc/sys/reboot.2,v 1.9.2.4 2001/12/14 18:34:01 ru Exp $ 30.\" 31.Dd November 23, 2017 32.Dt REBOOT 2 33.Os 34.Sh NAME 35.Nm reboot 36.Nd reboot system or halt processor 37.Sh LIBRARY 38.Lb libc 39.Sh SYNOPSIS 40.In unistd.h 41.In sys/reboot.h 42.Ft int 43.Fn reboot "int howto" 44.Sh DESCRIPTION 45.Fn Reboot 46reboots the system. 47Only the super-user may reboot a machine on demand. 48However, a reboot is invoked 49automatically in the event of unrecoverable system failures. 50.Pp 51.Fa Howto 52is a mask of options; the system call interface allows the following 53options, defined in the include file 54.In sys/reboot.h , 55to be passed 56to the new kernel or the new bootstrap and init programs. 57.Bl -tag -width RB_INITNAMEA 58.It Dv RB_AUTOBOOT 59The default, causing the system to reboot in its usual fashion. 60.It Dv RB_ASKNAME 61Interpreted by the bootstrap program itself, causing it to 62prompt on the console as to what file should be booted. 63Normally, the system is booted from the file 64.Dq Em xx Ns No (0,0)kernel , 65where 66.Em xx 67is the default disk name, 68without prompting for the file name. 69.It Dv RB_DFLTROOT 70Use the compiled in root device. 71Normally, the system uses the device from which it was booted 72as the root device if possible. 73(The default behavior is dependent on the ability of the bootstrap program 74to determine the drive from which it was loaded, which is not possible 75on all systems.) 76.It Dv RB_DUMP 77Dump kernel memory before rebooting; see 78.Xr savecore 8 79for more information. 80.It Dv RB_HALT 81the processor is simply halted; no reboot takes place. 82This option should be used with caution. 83.It Dv RB_POWEROFF 84After halting, the shutdown code will do what it can to turn 85off the power. 86This requires hardware support. 87.It Dv RB_INITNAME 88An option allowing the specification of an init program (see 89.Xr init 8 ) 90other than 91.Pa /sbin/init 92to be run when the system reboots. 93This switch is not currently available. 94.It Dv RB_KDB 95Load the symbol table and enable a built-in debugger in the system. 96This option will have no useful function if the kernel is not configured 97for debugging. 98Several other options have different meaning if combined 99with this option, although their use may not be possible 100via the 101.Fn reboot 102call. 103See 104.Xr ddb 4 105for more information. 106.It Dv RB_NOSYNC 107Normally, the disks are sync'd (see 108.Xr sync 8 ) 109before the processor is halted or rebooted. 110This option may be useful if file system changes have been made manually 111or if the processor is on fire. 112.It Dv RB_RDONLY 113Initially mount the root file system read-only. 114This is currently the default, and this option has been deprecated. 115.It Dv RB_SINGLE 116Normally, the reboot procedure involves an automatic disk consistency 117check and then multi-user operations. 118.Dv RB_SINGLE 119prevents this, booting the system with a single-user shell 120on the console. 121.Dv RB_SINGLE 122is actually interpreted by the 123.Xr init 8 124program in the newly booted system. 125.El 126.Pp 127When no options are given (i.e., 128.Dv RB_AUTOBOOT 129is used), the system is 130rebooted from file 131.Dq kernel 132in the root file system of unit 0 133of a disk chosen in a processor specific way. 134An automatic consistency check of the disks is normally performed 135(see 136.Xr fsck 8 ) . 137.Sh RETURN VALUES 138If successful, this call never returns. 139Otherwise, a -1 is returned and an error is returned in the global 140variable 141.Va errno . 142.Sh ERRORS 143.Bl -tag -width Er 144.It Bq Er EPERM 145The caller is not the super-user. 146.El 147.Sh SEE ALSO 148.Xr crash 8 , 149.Xr halt 8 , 150.Xr init 8 , 151.Xr reboot 8 , 152.Xr savecore 8 153.Sh HISTORY 154The 155.Fn reboot 156function call appeared in 157.Bx 4.0 . 158