1 .\" Copyright (c) 1998 Andries Brouwer (aeb@cwi.nl), 24 September 1998
3 .\" %%%LICENSE_START(VERBATIM)
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9 .\" manual under the conditions for verbatim copying, provided that the
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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14 .\" manual page may be incorrect or out-of-date.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
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18 .\" which is licensed free of charge, as they might when working
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25 .\" Modified, 27 May 2004, Michael Kerrisk <mtk.manpages@gmail.com>
26 .\" Added notes on capability requirements
28 .TH REBOOT 2 2015-02-01 "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 some of the constants involved have gotten
44 symbolic names RB_*, and the library call is a 1-argument
45 wrapper around the 3-argument system call: */
47 .B #include <unistd.h>
49 .B #include <sys/reboot.h>
51 .BI "int reboot(int " cmd );
55 call reboots the system, or enables/disables the reboot keystroke
56 (abbreviated CAD, since the default is Ctrl-Alt-Delete;
57 it can be changed using
60 This system call will fail (with
65 .B LINUX_REBOOT_MAGIC1
66 (that is, 0xfee1dead) and
69 .B LINUX_REBOOT_MAGIC2
71 However, since 2.1.17 also
72 .B LINUX_REBOOT_MAGIC2A
75 .B LINUX_REBOOT_MAGIC2B
78 .B LINUX_REBOOT_MAGIC2C
80 are permitted as values for
82 (The hexadecimal values of these constants are meaningful.)
86 argument can have the following values:
88 .B LINUX_REBOOT_CMD_CAD_OFF
89 .RB ( RB_DISABLE_CAD ,
92 This means that the CAD keystroke will cause a
95 sent to init (process 1), whereupon this process may decide upon a
96 proper action (maybe: kill all processes, sync, reboot).
98 .B LINUX_REBOOT_CMD_CAD_ON
102 This means that the CAD keystroke will immediately cause
103 the action associated with
104 .BR LINUX_REBOOT_CMD_RESTART .
106 .B LINUX_REBOOT_CMD_HALT
107 .RB ( RB_HALT_SYSTEM ,
108 0xcdef0123; since Linux 1.1.76).
109 The message "System halted." is printed, and the system is halted.
110 Control is given to the ROM monitor, if there is one.
115 .BR LINUX_REBOOT_CMD_KEXEC
117 0x45584543, since Linux 2.6.13).
118 Execute a kernel that has been loaded earlier with
120 This option is available only if the kernel was configured with
123 .B LINUX_REBOOT_CMD_POWER_OFF
125 0x4321fedc; since Linux 2.1.30).
126 The message "Power down." is printed, the system is stopped,
127 and all power is removed from the system, if possible.
132 .B LINUX_REBOOT_CMD_RESTART
135 The message "Restarting system." is printed, and a default
136 restart is performed immediately.
141 .B LINUX_REBOOT_CMD_RESTART2
142 (0xa1b2c3d4; since Linux 2.1.30).
143 The message "Restarting system with command \(aq%s\(aq" is printed,
144 and a restart (using the command string given in
146 is performed immediately.
151 .BR LINUX_REBOOT_CMD_SW_SUSPEND
152 .RB ( RB_SW_SUSPEND ,
153 0xd000fce1; since Linux 2.5.18).
154 The system is suspended (hibernated) to disk.
155 This option is available only if the kernel was configured with
156 .BR CONFIG_HIBERNATION .
158 Only the superuser may call
161 The precise effect of the above actions depends on the architecture.
162 For the i386 architecture, the additional argument does not do
163 anything at present (2.1.122), but the type of reboot can be
164 determined by kernel command-line arguments ("reboot=...") to be
165 either warm or cold, and either hard or through the BIOS.
166 .SS Behavior inside PID namespaces
167 .\" commit cf3f89214ef6a33fad60856bc5ffd7bb2fc4709b
168 .\" see also commit 923c7538236564c46ee80c253a416705321f13e3
169 Since Linux 3.4, when
171 is called from a PID namespace (see
172 .BR pid_namespaces (7))
173 other than the initial PID namespace,
174 the effect of the call is to send a signal to the namespace "init" process.
175 .BR LINUX_REBOOT_CMD_RESTART
177 .BR LINUX_REBOOT_CMD_RESTART2
181 .BR LINUX_REBOOT_CMD_POWER_OFF
183 .BR LINUX_REBOOT_CMD_HALT
190 that stop or restart the system,
196 values, zero is returned on success.
197 In all cases, \-1 is returned on failure, and
199 is set appropriately.
203 Problem with getting user-space data under
204 .BR LINUX_REBOOT_CMD_RESTART2 .
207 Bad magic numbers or \fIcmd\fP.
210 The calling process has insufficient privilege to call
214 capability is required.
218 and should not be used in programs intended to be portable.
223 .BR capabilities (7),
228 This page is part of release 3.79 of the Linux
231 A description of the project,
232 information about reporting bugs,
233 and the latest version of this page,
235 \%http://www.kernel.org/doc/man\-pages/.