reboot — reboot or enable/disable Ctrl-Alt-Del
/* 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); |
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 kernel command-line arguments ("reboot=...") to be either warm or cold, and either hard or through the BIOS.
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.
Problem with getting userspace data under
LINUX_REBOOT_CMD_RESTART2.
Bad magic numbers or cmd.
The calling process has insufficient privilege to
call reboot(); the
CAP_SYS_BOOT capability
is required.
reboot() is Linux-specific,
and should not be used in programs intended to be
portable.
This page is part of release 3.24 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/.
|
Copyright (c) 1998 Andries Brouwer (aebcwi.nl), 24 September 1998 Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. Modified, 27 May 2004, Michael Kerrisk <mtk.manpagesgmail.com> Added notes on capability requirements |