mirror of https://github.com/mkerrisk/man-pages
172 lines
5.0 KiB
Groff
172 lines
5.0 KiB
Groff
.\" Copyright (c) 1998 Andries Brouwer (aeb@cwi.nl), 24 September 1998
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" Modified, 27 May 2004, Michael Kerrisk <mtk.manpages@gmail.com>
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.\" Added notes on capability requirements
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.\"
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.TH REBOOT 2 2004-05-27 "Linux" "Linux Programmer's Manual"
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.SH NAME
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reboot \- reboot or enable/disable Ctrl-Alt-Del
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.SH SYNOPSIS
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/* For libc4 and libc5 the library call and the system call
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are identical, and since kernel version 2.1.30 there are
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symbolic names LINUX_REBOOT_* for the constants and a
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fourth argument to the call: */
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.sp
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.B #include <unistd.h>
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.br
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.B #include <linux/reboot.h>
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.sp
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.BI "int reboot(int " magic ", int " magic2 ", int " flag ", void *" arg );
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.sp
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/* Under glibc some of the constants involved have gotten
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symbolic names RB_*, and the library call is a 1-argument
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wrapper around the 3-argument system call: */
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.sp
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.B #include <unistd.h>
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.br
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.B #include <sys/reboot.h>
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.sp
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.BI "int reboot(int " flag );
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.SH DESCRIPTION
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The
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.BR reboot ()
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call reboots the system, or enables/disables the reboot keystroke
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(abbreviated CAD, since the default is Ctrl-Alt-Delete;
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it can be changed using
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.BR loadkeys (1)).
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.PP
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This system call will fail (with
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.BR EINVAL )
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unless
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.I magic
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equals
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.BR LINUX_REBOOT_MAGIC1
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(that is, 0xfee1dead) and
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.I magic2
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equals
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.BR LINUX_REBOOT_MAGIC2
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(that is, 672274793).
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However, since 2.1.17 also
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.BR LINUX_REBOOT_MAGIC2A
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(that is, 85072278)
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and since 2.1.97 also
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.BR LINUX_REBOOT_MAGIC2B
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(that is, 369367448)
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and since 2.5.71 also
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.BR LINUX_REBOOT_MAGIC2C
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(that is, 537993216)
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are permitted as value for
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.IR magic2 .
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(The hexadecimal values of these constants are meaningful.)
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The
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.I flag
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argument can have the following values:
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.TP
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.B LINUX_REBOOT_CMD_RESTART
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(RB_AUTOBOOT, 0x1234567).
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The message `Restarting system.' is printed, and a default
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restart is performed immediately.
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If not preceded by a
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.BR sync (2),
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data will be lost.
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.TP
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.B LINUX_REBOOT_CMD_HALT
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(RB_HALT_SYSTEM, 0xcdef0123; since 1.1.76).
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The message `System halted.' is printed, and the system is halted.
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Control is given to the ROM monitor, if there is one.
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If not preceded by a
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.BR sync (2),
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data will be lost.
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.TP
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.B LINUX_REBOOT_CMD_POWER_OFF
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(0x4321fedc; since 2.1.30).
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The message `Power down.' is printed, the system is stopped,
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and all power is removed from the system, if possible.
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If not preceded by a
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.BR sync (2),
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data will be lost.
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.TP
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.B LINUX_REBOOT_CMD_RESTART2
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(0xa1b2c3d4; since 2.1.30).
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The message `Restarting system with command '%s'' is printed,
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and a restart (using the command string given in
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.IR arg )
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is performed immediately.
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If not preceded by a
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.BR sync (2),
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data will be lost.
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.TP
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.B LINUX_REBOOT_CMD_CAD_ON
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(RB_ENABLE_CAD, 0x89abcdef).
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CAD is enabled.
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This means that the CAD keystroke will immediately cause
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the action associated with
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.BR LINUX_REBOOT_CMD_RESTART .
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.TP
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.B LINUX_REBOOT_CMD_CAD_OFF
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(RB_DISABLE_CAD, 0).
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CAD is disabled.
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This means that the CAD keystroke will cause a
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.B SIGINT
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signal to be
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sent to init (process 1), whereupon this process may decide upon a
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proper action (maybe: kill all processes, sync, reboot).
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.LP
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Only the superuser may use this function.
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.LP
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The precise effect of the above actions depends on the architecture.
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For the i386 architecture, the additional argument does not do
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anything at present (2.1.122), but the type of reboot can be
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determined by kernel command line arguments (`reboot=...') to be
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either warm or cold, and either hard or through the BIOS.
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.SH "RETURN VALUE"
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On success, zero is returned.
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On error, \-1 is returned, and
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.I errno
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is set appropriately.
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.SH ERRORS
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.TP
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.B EFAULT
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Problem with getting userspace data under
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.BR LINUX_REBOOT_CMD_RESTART2 .
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.TP
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.B EINVAL
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Bad magic numbers or \fIflag\fP.
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.TP
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.B EPERM
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The calling process has insufficient privilege to call
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.BR reboot ();
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the
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.B CAP_SYS_BOOT
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capability is required.
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.SH "CONFORMING TO"
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.BR reboot ()
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is Linux specific,
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and should not be used in programs intended to be portable.
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.SH "SEE ALSO"
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.BR sync (2),
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.BR bootparam (7),
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.BR capabilities (7),
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.BR ctrlaltdel (8),
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.BR halt (8),
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.BR reboot (8)
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