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 sym-
bolic 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
Under glibc some of the constants involved have gotten sym-
bolic 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 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 sys-
tem.' 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 mes-
sage `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 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
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)