REBOOT(2)                 FreeBSD System Calls Manual                REBOOT(2)

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     Normally the system only prompts the user if the loader
                    specified root file system has an error.  This flag forces
                    it to always prompt the user for the root partition.

     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_POWERCYCLE  After halting, the shutdown code will do what it can to
                    turn off the power and then turn the power back on.  This
                    requires hardware support, usually an auxiliary
                    microprocessor that can sequence the power supply.  At
                    present only the ipmi(4) driver implements this feature.

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

     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_REROOT      Instead of rebooting, unmount all filesystems except the
                    one containing currently-running executable, and mount
                    root filesystem using the same mechanism which is used
                    during normal boot, based on vfs.root.mountfrom kenv(1)
                    variable.

     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.

FreeBSD 13.1-RELEASE-p6          July 10, 2018         FreeBSD 13.1-RELEASE-p6