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1 | .\" Copyright (c) 1998 Andries Brouwer (aeb@cwi.nl), 24 September 1998 |
2 | .\" | |
93015253 | 3 | .\" %%%LICENSE_START(VERBATIM) |
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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. | |
7 | .\" | |
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. | |
c13182ef | 12 | .\" |
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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14 | .\" manual page may be incorrect or out-of-date.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 | |
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 | |
19 | .\" professionally. | |
c13182ef | 20 | .\" |
fea681da MK |
21 | .\" Formatted or processed versions of this manual, if unaccompanied by |
22 | .\" the source, must acknowledge the copyright and authors of this work. | |
4b72fb64 | 23 | .\" %%%LICENSE_END |
7822805d | 24 | .\" |
c11b1abf | 25 | .\" Modified, 27 May 2004, Michael Kerrisk <mtk.manpages@gmail.com> |
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26 | .\" Added notes on capability requirements |
27 | .\" | |
b8efb414 | 28 | .TH REBOOT 2 2016-10-08 "Linux" "Linux Programmer's Manual" |
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29 | .SH NAME |
30 | reboot \- reboot or enable/disable Ctrl-Alt-Del | |
31 | .SH SYNOPSIS | |
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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: */ | |
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36 | .sp |
37 | .B #include <unistd.h> | |
38 | .br | |
39 | .B #include <linux/reboot.h> | |
40 | .sp | |
350d584d | 41 | .BI "int reboot(int " magic ", int " magic2 ", int " cmd ", void *" arg ); |
fea681da | 42 | .sp |
25fe5693 CTV |
43 | /* Under glibc and most alternative libc's (including uclibc, dietlibc, |
44 | musl and a few others), some of the constants involved have gotten | |
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45 | symbolic names RB_*, and the library call is a 1-argument |
46 | wrapper around the 3-argument system call: */ | |
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47 | .sp |
48 | .B #include <unistd.h> | |
49 | .br | |
50 | .B #include <sys/reboot.h> | |
51 | .sp | |
350d584d | 52 | .BI "int reboot(int " cmd ); |
fea681da | 53 | .SH DESCRIPTION |
c13182ef | 54 | The |
e511ffb6 | 55 | .BR reboot () |
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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 | |
59 | .BR loadkeys (1)). | |
60 | .PP | |
682edefb MK |
61 | This system call will fail (with |
62 | .BR EINVAL ) | |
63 | unless | |
fea681da | 64 | .I magic |
682edefb | 65 | equals |
0daa9e92 | 66 | .B LINUX_REBOOT_MAGIC1 |
682edefb | 67 | (that is, 0xfee1dead) and |
fea681da | 68 | .I magic2 |
682edefb | 69 | equals |
0daa9e92 | 70 | .B LINUX_REBOOT_MAGIC2 |
682edefb MK |
71 | (that is, 672274793). |
72 | However, since 2.1.17 also | |
0daa9e92 | 73 | .B LINUX_REBOOT_MAGIC2A |
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74 | (that is, 85072278) |
75 | and since 2.1.97 also | |
0daa9e92 | 76 | .B LINUX_REBOOT_MAGIC2B |
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77 | (that is, 369367448) |
78 | and since 2.5.71 also | |
0daa9e92 | 79 | .B LINUX_REBOOT_MAGIC2C |
682edefb | 80 | (that is, 537993216) |
2b91ac79 | 81 | are permitted as values for |
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82 | .IR magic2 . |
83 | (The hexadecimal values of these constants are meaningful.) | |
352e737d | 84 | |
fea681da | 85 | The |
350d584d | 86 | .I cmd |
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87 | argument can have the following values: |
88 | .TP | |
939fd8db | 89 | .B LINUX_REBOOT_CMD_CAD_OFF |
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90 | .RB ( RB_DISABLE_CAD , |
91 | 0). | |
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92 | CAD is disabled. |
93 | This means that the CAD keystroke will cause a | |
94 | .B SIGINT | |
95 | signal to be | |
96 | sent to init (process 1), whereupon this process may decide upon a | |
97 | proper action (maybe: kill all processes, sync, reboot). | |
98 | .TP | |
99 | .B LINUX_REBOOT_CMD_CAD_ON | |
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100 | .RB ( RB_ENABLE_CAD , |
101 | 0x89abcdef). | |
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102 | CAD is enabled. |
103 | This means that the CAD keystroke will immediately cause | |
104 | the action associated with | |
105 | .BR LINUX_REBOOT_CMD_RESTART . | |
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106 | .TP |
107 | .B LINUX_REBOOT_CMD_HALT | |
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108 | .RB ( RB_HALT_SYSTEM , |
109 | 0xcdef0123; since Linux 1.1.76). | |
2d986c92 | 110 | The message "System halted." is printed, and the system is halted. |
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111 | Control is given to the ROM monitor, if there is one. |
112 | If not preceded by a | |
113 | .BR sync (2), | |
114 | data will be lost. | |
115 | .TP | |
d1d5d51c | 116 | .BR LINUX_REBOOT_CMD_KEXEC |
4cead6db | 117 | .RB ( RB_KEXEC , |
fd00f12c | 118 | 0x45584543, since Linux 2.6.13). |
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119 | Execute a kernel that has been loaded earlier with |
120 | .BR kexec_load (2). | |
33a0ccb2 | 121 | This option is available only if the kernel was configured with |
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122 | .BR CONFIG_KEXEC . |
123 | .TP | |
fea681da | 124 | .B LINUX_REBOOT_CMD_POWER_OFF |
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125 | .RB ( RB_POWER_OFF , |
126 | 0x4321fedc; since Linux 2.1.30). | |
2d986c92 | 127 | The message "Power down." is printed, the system is stopped, |
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128 | and all power is removed from the system, if possible. |
129 | If not preceded by a | |
130 | .BR sync (2), | |
131 | data will be lost. | |
132 | .TP | |
939fd8db | 133 | .B LINUX_REBOOT_CMD_RESTART |
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134 | .RB ( RB_AUTOBOOT , |
135 | 0x1234567). | |
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136 | The message "Restarting system." is printed, and a default |
137 | restart is performed immediately. | |
138 | If not preceded by a | |
139 | .BR sync (2), | |
140 | data will be lost. | |
141 | .TP | |
fea681da | 142 | .B LINUX_REBOOT_CMD_RESTART2 |
0b23bb07 | 143 | (0xa1b2c3d4; since Linux 2.1.30). |
9708eb37 | 144 | The message "Restarting system with command \(aq%s\(aq" is printed, |
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145 | and a restart (using the command string given in |
146 | .IR arg ) | |
147 | is performed immediately. | |
148 | If not preceded by a | |
149 | .BR sync (2), | |
150 | data will be lost. | |
2d37a960 | 151 | .TP |
d3532647 | 152 | .BR LINUX_REBOOT_CMD_SW_SUSPEND |
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153 | .RB ( RB_SW_SUSPEND , |
154 | 0xd000fce1; since Linux 2.5.18). | |
2d37a960 EDB |
155 | The system is suspended (hibernated) to disk. |
156 | This option is available only if the kernel was configured with | |
157 | .BR CONFIG_HIBERNATION . | |
fea681da | 158 | .LP |
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159 | Only the superuser may call |
160 | .BR reboot (). | |
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161 | .LP |
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 | |
84c517a4 | 165 | determined by kernel command-line arguments ("reboot=...") to be |
fea681da | 166 | either warm or cold, and either hard or through the BIOS. |
50f31881 | 167 | .SS Behavior inside PID namespaces |
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168 | .\" commit cf3f89214ef6a33fad60856bc5ffd7bb2fc4709b |
169 | .\" see also commit 923c7538236564c46ee80c253a416705321f13e3 | |
170 | Since Linux 3.4, when | |
50f31881 MK |
171 | .BR reboot () |
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. | |
176 | .BR LINUX_REBOOT_CMD_RESTART | |
177 | and | |
178 | .BR LINUX_REBOOT_CMD_RESTART2 | |
179 | cause a | |
180 | .BR SIGHUP | |
181 | signal to be sent. | |
182 | .BR LINUX_REBOOT_CMD_POWER_OFF | |
183 | and | |
184 | .BR LINUX_REBOOT_CMD_HALT | |
185 | cause a | |
186 | .B SIGINT | |
187 | signal to be sent. | |
90e072b6 WL |
188 | For the other |
189 | .I cmd | |
190 | values, \-1 is returned and | |
191 | .I errno | |
192 | is set to | |
193 | .BR EINVAL . | |
47297adb | 194 | .SH RETURN VALUE |
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195 | For the values of |
196 | .I cmd | |
197 | that stop or restart the system, | |
198 | a successful call to | |
199 | .BR reboot () | |
200 | does not return. | |
201 | For the other | |
202 | .I cmd | |
203 | values, zero is returned on success. | |
204 | In all cases, \-1 is returned on failure, and | |
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205 | .I errno |
206 | is set appropriately. | |
207 | .SH ERRORS | |
208 | .TP | |
209 | .B EFAULT | |
7fac88a9 | 210 | Problem with getting user-space data under |
682edefb | 211 | .BR LINUX_REBOOT_CMD_RESTART2 . |
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212 | .TP |
213 | .B EINVAL | |
350d584d | 214 | Bad magic numbers or \fIcmd\fP. |
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215 | .TP |
216 | .B EPERM | |
c13182ef | 217 | The calling process has insufficient privilege to call |
e511ffb6 | 218 | .BR reboot (); |
a0b4ac2c | 219 | the caller must have the |
fea681da | 220 | .B CAP_SYS_BOOT |
a0b4ac2c | 221 | inside its user namespace. |
47297adb | 222 | .SH CONFORMING TO |
e511ffb6 | 223 | .BR reboot () |
8382f16d | 224 | is Linux-specific, |
97c1eac8 | 225 | and should not be used in programs intended to be portable. |
47297adb | 226 | .SH SEE ALSO |
260be1fe | 227 | .BR kexec_load (2), |
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228 | .BR sync (2), |
229 | .BR bootparam (7), | |
230 | .BR capabilities (7), | |
231 | .BR ctrlaltdel (8), | |
232 | .BR halt (8), | |
233 | .BR reboot (8) |