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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.\" $FreeBSD$ 30.\" 31.Dd September 18, 2015 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 45The 46.Fn reboot 47system call 48reboots the system. 49Only the super-user may reboot a machine on demand. 50However, a reboot is invoked 51automatically in the event of unrecoverable system failures. 52.Pp 53The 54.Fa howto 55argument 56is a mask of options; the system call interface allows the following 57options, defined in the include file 58.In sys/reboot.h , 59to be passed 60to the new kernel or the new bootstrap and init programs. 61.Bl -tag -width RB_INITNAMEA 62.It Dv RB_AUTOBOOT 63The default, causing the system to reboot in its usual fashion. 64.It Dv RB_ASKNAME 65Interpreted by the bootstrap program itself, causing it to 66prompt on the console as to what file should be booted. 67Normally, the system is booted from the file 68.Dq Ar xx Ns No (0,0)kernel , 69where 70.Ar xx 71is the default disk name, 72without prompting for the file name. 73.It Dv RB_DFLTROOT 74Use the compiled in root device. 75Normally, the system uses the device from which it was booted 76as the root device if possible. 77(The default behavior is dependent on the ability of the bootstrap program 78to determine the drive from which it was loaded, which is not possible 79on all systems.) 80.It Dv RB_DUMP 81Dump kernel memory before rebooting; see 82.Xr savecore 8 83for more information. 84.It Dv RB_HALT 85The processor is simply halted; no reboot takes place. 86This option should be used with caution. 87.It Dv RB_POWEROFF 88After halting, the shutdown code will do what it can to turn 89off the power. 90This requires hardware support. 91.It Dv RB_INITNAME 92An option allowing the specification of an init program (see 93.Xr init 8 ) 94other than 95.Pa /sbin/init 96to be run when the system reboots. 97This switch is not currently available. 98.It Dv RB_KDB 99Load the symbol table and enable a built-in debugger in the system. 100This option will have no useful function if the kernel is not configured 101for debugging. 102Several other options have different meaning if combined 103with this option, although their use may not be possible 104via the 105.Fn reboot 106system call. 107See 108.Xr ddb 4 109for more information. 110.It Dv RB_NOSYNC 111Normally, the disks are sync'd (see 112.Xr sync 8 ) 113before the processor is halted or rebooted. 114This option may be useful if file system changes have been made manually 115or if the processor is on fire. 116.It Dv RB_REROOT 117Instead of rebooting, unmount all filesystems except the one containing 118currently-running executable, and mount root filesystem using the same 119mechanism which is used during normal boot, based on 120vfs.root.mountfrom 121.Xr kenv 8 122variable. 123.It Dv RB_RDONLY 124Initially mount the root file system read-only. 125This is currently the default, and this option has been deprecated. 126.It Dv RB_SINGLE 127Normally, the reboot procedure involves an automatic disk consistency 128check and then multi-user operations. 129.Dv RB_SINGLE 130prevents this, booting the system with a single-user shell 131on the console. 132.Dv RB_SINGLE 133is actually interpreted by the 134.Xr init 8 135program in the newly booted system. 136.El 137.Pp 138When no options are given (i.e., 139.Dv RB_AUTOBOOT 140is used), the system is 141rebooted from file 142.Dq kernel 143in the root file system of unit 0 144of a disk chosen in a processor specific way. 145An automatic consistency check of the disks is normally performed 146(see 147.Xr fsck 8 ) . 148.Sh RETURN VALUES 149If successful, this call never returns. 150Otherwise, a -1 is returned and an error is returned in the global 151variable 152.Va errno . 153.Sh ERRORS 154.Bl -tag -width Er 155.It Bq Er EPERM 156The caller is not the super-user. 157.El 158.Sh SEE ALSO 159.Xr crash 8 , 160.Xr halt 8 , 161.Xr init 8 , 162.Xr reboot 8 , 163.Xr savecore 8 164.Sh HISTORY 165The 166.Fn reboot 167system call appeared in 168.Bx 4.0 . 169