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REBOOT(2)                   BSD System Calls Manual                  REBOOT(2)

NAME
     reboot -- reboot system or halt processor

SYNOPSIS
     #include <&lt;unistd.h>&gt;
     #include <&lt;sys/reboot.h>&gt;

     int
     reboot(int howto);

DESCRIPTION
     reboot() reboots the system.  Only the superuser may reboot a machine on
     demand.  However, a reboot is invoked automatically in the event of unre-
     coverable system failures.

     howto is a mask of options; the system call interface allows the follow-
     ing options, defined in the include file <sys/reboot.h>, to be passed to
     the new kernel or the new bootstrap and init programs.

     RB_AUTOBOOT   The default, causing the system to reboot in its usual
                   fashion.

     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
                   ``xx(0,0)bsd'', where xx is the default disk name, without
                   prompting for the file name.

     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 abil-
                   ity of the bootstrap program to determine the drive from
                   which it was loaded, which is not possible on all systems.)

     RB_DUMP       Dump kernel memory before rebooting; see savecore(8) for
                   more information.

     RB_HALT       The processor is simply halted; no reboot takes place.

     RB_POWERDOWN  If used in conjunction with RB_HALT, and if the system
                   hardware supports the function, the system will be powered
                   off.

     RB_USERREQ    By default, the system will halt if reboot() is called dur-
                   ing startup (before the system has finished autoconfigura-
                   tion), even if RB_HALT is not specified.  This is because
                   panic(9)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
                   ddb(4) boot reboot command), so the system will reboot if a
                   halt is not explicitly requested.

     RB_INITNAME   An option allowing the specification of an init program
                   (see init(8)) other than /sbin/init to be run when the sys-
                   tem reboots.  This switch is not currently available.

     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
                   reboot() call.  See ddb(4) for more information.

     RB_NOSYNC     Normally, the disks are sync'd (see 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.

     RB_RDONLY     Initially mount the root file system read-only.  This is
                   currently the default, and this option has been deprecated.

     RB_SINGLE     Normally, the reboot procedure involves an automatic disk
                   consistency check and then multi-user operations.
                   RB_SINGLE prevents this, booting the system with a single-
                   user shell on the console.  RB_SINGLE is actually inter-
                   preted by the init(8) program in the newly booted system.

                   When no options are given (i.e., 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 per-
                   formed (see fsck(8)).

RETURN VALUES
     If successful, this call never returns.  Otherwise, a -1 is returned and
     an error is returned in the global variable errno.

ERRORS
     [EPERM]            The caller is not the superuser.

SEE ALSO
     ddb(4), crash(8), halt(8), init(8), reboot(8), savecore(8), boot(9),
     panic(9)

HISTORY
     The reboot() system call finally appeared in 4.0BSD.

BUGS
     Not all platforms support all possible arguments.

BSD                             April 29, 2017                             BSD