REBOOT(2)						     Linux Programmer's Manual							 REBOOT(2)

NAME

       reboot - reboot or enable/disable Ctrl-Alt-Del

SYNOPSIS

       For  libc4  and	libc5  the  library  call  and	the  system  call  are identical, and since kernel version 2.1.30 there are symbolic names
       LINUX_REBOOT_* for the constants and a fourth argument to the call:

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

       int reboot(int magic, int magic2, int flag, void *arg);

       Under glibc some of the constants involved have gotten symbolic names RB_*, and the library call is a 1-argument wrapper around the 3-argu-
       ment system call:

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

       int reboot(int flag);

DESCRIPTION

       The reboot call reboots the system, or enables/disables the reboot keystroke (abbreviated CAD, since the default is Ctrl-Alt-Delete; it can
       be changed using loadkeys(1)).

       This  system  call  will  fail  (with  EINVAL)  unless  magic  equals  LINUX_REBOOT_MAGIC1  (that  is,  0xfee1dead)   and   magic2   equals
       LINUX_REBOOT_MAGIC2  (that  is,	672274793).   However,	since  2.1.17  also LINUX_REBOOT_MAGIC2A (that is, 85072278) and since 2.1.97 also
       LINUX_REBOOT_MAGIC2B (that is, 369367448) are permitted as value for magic2.  (The hexadecimal values of these constants  are  meaningful.)
       The flag argument can have the following values:

       LINUX_REBOOT_CMD_RESTART
	      (RB_AUTOBOOT, 0x1234567).  The message `Restarting system.' is printed, and a default restart is performed immediately.  If not pre-
	      ceded by a sync(2), data will be lost.

       LINUX_REBOOT_CMD_HALT
	      (RB_HALT_SYSTEM, 0xcdef0123; since 1.1.76).  The message `System halted.' is printed, and the system is halted.  Control is given to
	      the ROM monitor, if there is one.  If not preceded by a sync(2), data will be lost.

       LINUX_REBOOT_CMD_POWER_OFF
	      (0x4321fedc;  since 2.1.30).  The message `Power down.' is printed, the system is stopped, and all power is removed from the system,
	      if possible.  If not preceded by a sync(2), data will be lost.

       LINUX_REBOOT_CMD_RESTART2
	      (0xa1b2c3d4; since 2.1.30).  The message `Restarting system with command '%s'' is printed, and a restart (using the  command  string
	      given in arg) is performed immediately.  If not preceded by a sync(2), data will be lost.

       LINUX_REBOOT_CMD_CAD_ON
	      (RB_ENABLE_CAD,  0x89abcdef).   CAD  is  enabled.  This means that the CAD keystroke will immediately cause the action associated to
	      LINUX_REBOOT_CMD_RESTART.

       LINUX_REBOOT_CMD_CAD_OFF
	      (RB_DISABLE_CAD, 0).  CAD is disabled.  This means that the CAD keystroke will cause a SIGINT signal to be sent to init (process 1),
	      whereupon this process may decide upon a proper action (maybe: kill all processes, sync, reboot).

       Only the super-user may use this function.

       The  precise  effect of the above actions depends on the architecture.  For the i386 architecture, the additional argument does not do any-
       thing at present (2.1.122), but the type of reboot can be determined by kernel command line arguments (`reboot=...') to be either  warm	or
       cold, and either hard or through the BIOS.

RETURN VALUE

       On success, zero is returned.  On error, -1 is returned, and errno is set appropriately.

ERRORS

       EINVAL Bad magic numbers or flag.

       EPERM  A non-root user attempts to call reboot.

CONFORMING TO

       reboot is Linux specific, and should not be used in programs intended to be portable.

SEE ALSO

       sync(2), bootparam(7), ctrlaltdel(8), halt(8), reboot(8)

Linux 2.1.122							    1998-09-24								 REBOOT(2)