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NAME

     reboot — reboot system or halt processor

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <unistd.h>
     #include <sys/reboot.h>

     int
     reboot(int howto);

DESCRIPTION

     The reboot() system call reboots the system.  Only the super-user may reboot a machine on
     demand.  However, a reboot is invoked automatically in the event of unrecoverable system
     failures.

     The howto argument is a mask of options; the system call interface allows the following
     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)kernel”, 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 ability 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.  This option should be
                   used with caution.

     RB_POWEROFF   After halting, the shutdown code will do what it can to turn off the power.
                   This requires hardware support.

     RB_INITNAME   An option allowing the specification of an init program (see init(8)) other
                   than /sbin/init to be run when the system 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() system 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 interpreted 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
     “kernel” 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 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 super-user.

SEE ALSO

     crash(8), halt(8), init(8), reboot(8), savecore(8)

HISTORY

     The reboot() system call appeared in 4.0BSD.

BUGS

     The HP300 implementation supports neither RB_DFLTROOT nor RB_KDB.