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.\" Copyright (c) 1998 Andries Brouwer (aeb@cwi.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.\" manual page may be incorrect or out-of-date.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.
.\"
.TH REBOOT 2 "24 September 1998" "Linux 2.1.122" "Linux Programmer's Manual"
.SH NAME
reboot \- reboot or enable/disable Ctrl-Alt-Del
.SH 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:
.sp
.B #include <unistd.h>
.br
.B #include <linux/reboot.h>
.sp
.BI "int reboot (int " magic ", int " magic2 ", int " flag ", void *" arg );
.sp
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:
.sp
.B #include <unistd.h>
.br
.B #include <sys/reboot.h>
.sp
.BI "int reboot (int " flag );
.SH DESCRIPTION
The
.B 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
.BR loadkeys (1)).
.PP
This system call will fail (with EINVAL) unless
.I magic
equals LINUX_REBOOT_MAGIC1 (that is, 0xfee1dead) and
.I 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
.IR magic2 .
(The hexadecimal values of these constants are meaningful.)
The
.I flag
argument can have the following values:
.TP
.B 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
.BR sync (2),
data will be lost.
.TP
.B 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
.BR sync (2),
data will be lost.
.TP
.B 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
.BR sync (2),
data will be lost.
.TP
.B 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
.IR arg )
is performed immediately.
If not preceded by a
.BR sync (2),
data will be lost.
.TP
.B 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.
.TP
.B 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).
.LP
Only the super-user may use this function.
.LP
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.
.SH "RETURN VALUE"
On success, zero is returned. On error, \-1 is returned, and
.I errno
is set appropriately.
.SH ERRORS
.TP
.B EINVAL
Bad magic numbers or \fIflag\fP.
.TP
.B EPERM
A non-root user attempts to call
.BR reboot .
.SH "CONFORMING TO"
.B reboot
is Linux specific, and should not be used in programs intended to be portable.
.SH "SEE ALSO"
.BR sync (2),
.BR bootparam (7),
.BR ctrlaltdel (8),
.BR halt (8),
.BR reboot (8)
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