1 .\" Copyright (c) 1998 Andries Brouwer (aeb@cwi.nl), 24 September 1998
3 .\" %%%LICENSE_START(VERBATIM)
4 .\" Permission is granted to make and distribute verbatim copies of this
5 .\" manual provided the copyright notice and this permission notice are
6 .\" preserved on all copies.
8 .\" Permission is granted to copy and distribute modified versions of this
9 .\" manual under the conditions for verbatim copying, provided that the
10 .\" entire resulting derived work is distributed under the terms of a
11 .\" permission notice identical to this one.
13 .\" Since the Linux kernel and libraries are constantly changing, this
14 .\" manual page may be incorrect or out-of-date. The author(s) assume no
15 .\" responsibility for errors or omissions, or for damages resulting from
16 .\" the use of the information contained herein. The author(s) may not
17 .\" have taken the same level of care in the production of this manual,
18 .\" which is licensed free of charge, as they might when working
21 .\" Formatted or processed versions of this manual, if unaccompanied by
22 .\" the source, must acknowledge the copyright and authors of this work.
25 .\" Modified, 27 May 2004, Michael Kerrisk <mtk.manpages@gmail.com>
26 .\" Added notes on capability requirements
28 .TH REBOOT 2 2016-10-08 "Linux" "Linux Programmer's Manual"
30 reboot \- reboot or enable/disable Ctrl-Alt-Del
32 /* For libc4 and libc5 the library call and the system call
33 are identical, and since kernel version 2.1.30 there are
34 symbolic names LINUX_REBOOT_* for the constants and a
35 fourth argument to the call: */
37 .B #include <unistd.h>
39 .B #include <linux/reboot.h>
41 .BI "int reboot(int " magic ", int " magic2 ", int " cmd ", void *" arg );
43 /* Under glibc and most alternative libc's (including uclibc, dietlibc,
44 musl and a few others), some of the constants involved have gotten
45 symbolic names RB_*, and the library call is a 1-argument
46 wrapper around the 3-argument system call: */
48 .B #include <unistd.h>
50 .B #include <sys/reboot.h>
52 .BI "int reboot(int " cmd );
56 call reboots the system, or enables/disables the reboot keystroke
57 (abbreviated CAD, since the default is Ctrl-Alt-Delete;
58 it can be changed using
61 This system call will fail (with
66 .B LINUX_REBOOT_MAGIC1
67 (that is, 0xfee1dead) and
70 .B LINUX_REBOOT_MAGIC2
72 However, since 2.1.17 also
73 .B LINUX_REBOOT_MAGIC2A
76 .B LINUX_REBOOT_MAGIC2B
79 .B LINUX_REBOOT_MAGIC2C
81 are permitted as values for
83 (The hexadecimal values of these constants are meaningful.)
87 argument can have the following values:
89 .B LINUX_REBOOT_CMD_CAD_OFF
90 .RB ( RB_DISABLE_CAD ,
93 This means that the CAD keystroke will cause a
96 sent to init (process 1), whereupon this process may decide upon a
97 proper action (maybe: kill all processes, sync, reboot).
99 .B LINUX_REBOOT_CMD_CAD_ON
100 .RB ( RB_ENABLE_CAD ,
103 This means that the CAD keystroke will immediately cause
104 the action associated with
105 .BR LINUX_REBOOT_CMD_RESTART .
107 .B LINUX_REBOOT_CMD_HALT
108 .RB ( RB_HALT_SYSTEM ,
109 0xcdef0123; since Linux 1.1.76).
110 The message "System halted." is printed, and the system is halted.
111 Control is given to the ROM monitor, if there is one.
116 .BR LINUX_REBOOT_CMD_KEXEC
118 0x45584543, since Linux 2.6.13).
119 Execute a kernel that has been loaded earlier with
121 This option is available only if the kernel was configured with
124 .B LINUX_REBOOT_CMD_POWER_OFF
126 0x4321fedc; since Linux 2.1.30).
127 The message "Power down." is printed, the system is stopped,
128 and all power is removed from the system, if possible.
133 .B LINUX_REBOOT_CMD_RESTART
136 The message "Restarting system." is printed, and a default
137 restart is performed immediately.
142 .B LINUX_REBOOT_CMD_RESTART2
143 (0xa1b2c3d4; since Linux 2.1.30).
144 The message "Restarting system with command \(aq%s\(aq" is printed,
145 and a restart (using the command string given in
147 is performed immediately.
152 .BR LINUX_REBOOT_CMD_SW_SUSPEND
153 .RB ( RB_SW_SUSPEND ,
154 0xd000fce1; since Linux 2.5.18).
155 The system is suspended (hibernated) to disk.
156 This option is available only if the kernel was configured with
157 .BR CONFIG_HIBERNATION .
159 Only the superuser may call
162 The precise effect of the above actions depends on the architecture.
163 For the i386 architecture, the additional argument does not do
164 anything at present (2.1.122), but the type of reboot can be
165 determined by kernel command-line arguments ("reboot=...") to be
166 either warm or cold, and either hard or through the BIOS.
167 .SS Behavior inside PID namespaces
168 .\" commit cf3f89214ef6a33fad60856bc5ffd7bb2fc4709b
169 .\" see also commit 923c7538236564c46ee80c253a416705321f13e3
170 Since Linux 3.4, when
172 is called from a PID namespace (see
173 .BR pid_namespaces (7))
174 other than the initial PID namespace,
175 the effect of the call is to send a signal to the namespace "init" process.
177 .BR LINUX_REBOOT_CMD_RESTART
179 .BR LINUX_REBOOT_CMD_RESTART2
185 .BR LINUX_REBOOT_CMD_POWER_OFF
187 .BR LINUX_REBOOT_CMD_HALT
194 values, \-1 is returned and
201 that stop or restart the system,
207 values, zero is returned on success.
208 In all cases, \-1 is returned on failure, and
210 is set appropriately.
214 Problem with getting user-space data under
215 .BR LINUX_REBOOT_CMD_RESTART2 .
218 Bad magic numbers or \fIcmd\fP.
221 The calling process has insufficient privilege to call
223 the caller must have the
225 inside its user namespace.
229 and should not be used in programs intended to be portable.
234 .BR capabilities (7),