1REBOOT(2) Linux Programmer's Manual REBOOT(2)
2
6 reboot - reboot or enable/disable Ctrl-Alt-Del
7
9 /* For libc4 and libc5 the library call and the system call
10 are identical, and since kernel version 2.1.30 there are
11 symbolic names LINUX_REBOOT_* for the constants and a
12 fourth argument to the call: */
13 #include <unistd.h>
15 #include <linux/reboot.h>
16 int reboot(int magic, int magic2, int cmd, void *arg);
18 /* Under glibc some of the constants involved have gotten
20 symbolic names RB_*, and the library call is a 1-argument
21 wrapper around the 3-argument system call: */
22 #include <unistd.h>
24 #include <sys/reboot.h>
25 int reboot(int cmd);
27
29 The reboot() call reboots the system, or enables/disables the reboot
30 keystroke (abbreviated CAD, since the default is Ctrl-Alt-Delete; it
31 can be changed using loadkeys(1)).
32 This system call will fail (with EINVAL) unless magic equals
34 LINUX_REBOOT_MAGIC1 (that is, 0xfee1dead) and magic2 equals
35 LINUX_REBOOT_MAGIC2 (that is, 672274793). However, since 2.1.17 also
36 LINUX_REBOOT_MAGIC2A (that is, 85072278) and since 2.1.97 also
37 LINUX_REBOOT_MAGIC2B (that is, 369367448) and since 2.5.71 also
38 LINUX_REBOOT_MAGIC2C (that is, 537993216) are permitted as value for
39 magic2. (The hexadecimal values of these constants are meaningful.)
40 The cmd argument can have the following values:
41 LINUX_REBOOT_CMD_RESTART
43 (RB_AUTOBOOT, 0x1234567). The message "Restarting system." is
44 printed, and a default restart is performed immediately. If not
45 preceded by a sync(2), data will be lost.
46 LINUX_REBOOT_CMD_HALT
48 (RB_HALT_SYSTEM, 0xcdef0123; since 1.1.76). The message "System
49 halted." is printed, and the system is halted. Control is given
50 to the ROM monitor, if there is one. If not preceded by a
51 sync(2), data will be lost.
52 LINUX_REBOOT_CMD_POWER_OFF
54 (0x4321fedc; since 2.1.30). The message "Power down." is
55 printed, the system is stopped, and all power is removed from
56 the system, if possible. If not preceded by a sync(2), data
57 will be lost.
58 LINUX_REBOOT_CMD_RESTART2
60 (0xa1b2c3d4; since 2.1.30). The message "Restarting system with
61 command '%s'" is printed, and a restart (using the command
62 string given in arg) is performed immediately. If not preceded
63 by a sync(2), data will be lost.
64 LINUX_REBOOT_CMD_CAD_ON
66 (RB_ENABLE_CAD, 0x89abcdef). CAD is enabled. This means that
67 the CAD keystroke will immediately cause the action associated
68 with LINUX_REBOOT_CMD_RESTART.
69 LINUX_REBOOT_CMD_CAD_OFF
71 (RB_DISABLE_CAD, 0). CAD is disabled. This means that the CAD
72 keystroke will cause a SIGINT signal to be sent to init (process
73 1), whereupon this process may decide upon a proper action
74 (maybe: kill all processes, sync, reboot).
75 Only the superuser may call reboot().
77 The precise effect of the above actions depends on the architecture.
79 For the i386 architecture, the additional argument does not do anything
80 at present (2.1.122), but the type of reboot can be determined by ker‐
81 nel command-line arguments ("reboot=...") to be either warm or cold,
82 and either hard or through the BIOS.
83
85 For the values of cmd that stop or restart the system, a successful
86 call to reboot() does not return. For the other cmd values, zero is
87 returned on success. In all cases, -1 is returned on failure, and
88 errno is set appropriately.
89
91 EFAULT Problem with getting userspace data under
92 LINUX_REBOOT_CMD_RESTART2.
93 EINVAL Bad magic numbers or cmd.
95 EPERM The calling process has insufficient privilege to call reboot();
97 the CAP_SYS_BOOT capability is required.
98
100 reboot() is Linux-specific, and should not be used in programs intended
101 to be portable.
102
104 sync(2), bootparam(7), capabilities(7), ctrlaltdel(8), halt(8),
105 reboot(8)
106
108 This page is part of release 3.22 of the Linux man-pages project. A
109 description of the project, and information about reporting bugs, can
110 be found at http://www.kernel.org/doc/man-pages/.
111Linux 2008-02-11 REBOOT(2)