luther@gliethttp:~$ vim /usr/include/sys/reboot.h /* Copyright (C) 1996, 1997, 1998, 1999 Free Software Foundation, Inc. This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License along with the GNU C Library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. */
/* This file should define RB_* macros to be used as flag bits in the argument to the `reboot' system call. */
#ifndef _SYS_REBOOT_H #define _SYS_REBOOT_H 1
#include
/* Perform a hard reset now. */ #define RB_AUTOBOOT 0x01234567
/* Halt the system. */ #define RB_HALT_SYSTEM 0xcdef0123
/* Enable reboot using Ctrl-Alt-Delete keystroke. */ #define RB_ENABLE_CAD 0x89abcdef
/* Disable reboot using Ctrl-Alt-Delete keystroke. */ #define RB_DISABLE_CAD 0
/* Stop system and switch power off if possible. */ #define RB_POWER_OFF 0x4321fedc
__BEGIN_DECLS
/* Reboot or halt the system. */ extern int reboot (int __howto) __THROW;
__END_DECLS
#endif /* _SYS_REBOOT_H */
luther@gliethttp:~$ man 2 reboot
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 #include
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 #include
int reboot(int cmd);
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) and since 2.5.71 also LINUX_REBOOT_MAGIC2C (that is, 537993216) are permitted as value for magic2. (The hexadecimal values of these constants are meaningful.) The cmd 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 preceded 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 with 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 superuser may call reboot().
The precise effect of the above actions depends on the architecture. For the i386 architecture, the additional argument does not do anything at present (2.1.122), but the type of reboot can be determined by ker‐ nel 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 userspace 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 3.01 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at
