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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 cmd, 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-argument system call: */

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

       int reboot(int cmd);

DESCRIPTION
       The  reboot()  call reboots the system, or enables/disables the reboot keystroke (abbrevi-
       ated 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) and since 2.5.71 also LINUX_REBOOT_MAGIC2C (that
       is, 537993216) are permitted as value for magic2.  (The hexadecimal values of  these  con-
       stants are meaningful.)	The cmd argument can have the following values:

       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).

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

       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_KEXEC (since Linux 2.6.13)
	      Execute a kernel that has been loaded earlier with kexec_load(2).  This  option  is
	      available only if the kernel was configured with CONFIG_KEXEC.

       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_RESTART
	      (RB_AUTOBOOT,  0x1234567).   The	message  "Restarting  system."	is printed, and a
	      default restart is performed immediately.  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 immedi-
	      ately.  If not preceded by a sync(2), data will be lost.

       Only the superuser may call reboot().

       The  precise effect of the above actions depends on the architecture.  For the i386 archi-
       tecture, the additional argument does not do anything 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
       For the values of cmd that stop or restart the system, a successful call to reboot()  does
       not  return.   For the other cmd values, zero is returned on success.  In all cases, -1 is
       returned on failure, and errno is set appropriately.

ERRORS
       EFAULT Problem with getting user-space data under LINUX_REBOOT_CMD_RESTART2.

       EINVAL Bad magic numbers or cmd.

       EPERM  The calling process has insufficient privilege to call reboot();	the  CAP_SYS_BOOT
	      capability is required.

CONFORMING TO
       reboot() is Linux-specific, and should not be used in programs intended to be portable.

SEE ALSO
       sync(2), bootparam(7), capabilities(7), ctrlaltdel(8), halt(8), reboot(8)

COLOPHON
       This  page  is  part of release 3.53 of the Linux man-pages project.  A description of the
       project,    and	  information	 about	  reporting    bugs,	can    be    found     at
       http://www.kernel.org/doc/man-pages/.

Linux					    2010-10-31					REBOOT(2)
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