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.

Debian                                            July 10, 2018                                        REBOOT(2)