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 are identical,
10 and since kernel version 2.1.30 there are symbolic names LINUX_REBOOT_*
11 for the constants and a fourth argument to the call:
12 #include <unistd.h>
14 #include <linux/reboot.h>
15 int reboot(int magic, int magic2, int flag, void *arg);
17 Under glibc some of the constants involved have gotten symbolic names
19 RB_*, and the library call is a 1-argument wrapper around the 3-argu‐
20 ment system call:
21 #include <unistd.h>
23 #include <sys/reboot.h>
24 int reboot(int flag);
26
28 The reboot() call reboots the system, or enables/disables the reboot
29 keystroke (abbreviated CAD, since the default is Ctrl-Alt-Delete; it
30 can be changed using loadkeys(1)).
31 This system call will fail (with EINVAL) unless magic equals
33 LINUX_REBOOT_MAGIC1 (that is, 0xfee1dead) and magic2 equals
34 LINUX_REBOOT_MAGIC2 (that is, 672274793). However, since 2.1.17 also
35 LINUX_REBOOT_MAGIC2A (that is, 85072278) and since 2.1.97 also
36 LINUX_REBOOT_MAGIC2B (that is, 369367448) and since 2.5.71 also
37 LINUX_REBOOT_MAGIC2C (that is, 537993216) are permitted as value for
38 magic2. (The hexadecimal values of these constants are meaningful.)
39 The flag argument can have the following values:
40 LINUX_REBOOT_CMD_RESTART
42 (RB_AUTOBOOT, 0x1234567). The message `Restarting system.' is
43 printed, and a default restart is performed immediately. If not
44 preceded by a sync(2), data will be lost.
45 LINUX_REBOOT_CMD_HALT
47 (RB_HALT_SYSTEM, 0xcdef0123; since 1.1.76). The message `System
48 halted.' is printed, and the system is halted. Control is given
49 to the ROM monitor, if there is one. If not preceded by a
50 sync(2), data will be lost.
51 LINUX_REBOOT_CMD_POWER_OFF
53 (0x4321fedc; since 2.1.30). The message `Power down.' is
54 printed, the system is stopped, and all power is removed from
55 the system, if possible. If not preceded by a sync(2), data
56 will be lost.
57 LINUX_REBOOT_CMD_RESTART2
59 (0xa1b2c3d4; since 2.1.30). The message `Restarting system with
60 command '%s'' is printed, and a restart (using the command
61 string given in arg) is performed immediately. If not preceded
62 by a sync(2), data will be lost.
63 LINUX_REBOOT_CMD_CAD_ON
65 (RB_ENABLE_CAD, 0x89abcdef). CAD is enabled. This means that
66 the CAD keystroke will immediately cause the action associated
67 with LINUX_REBOOT_CMD_RESTART.
68 LINUX_REBOOT_CMD_CAD_OFF
70 (RB_DISABLE_CAD, 0). CAD is disabled. This means that the CAD
71 keystroke will cause a SIGINT signal to be sent to init (process
72 1), whereupon this process may decide upon a proper action
73 (maybe: kill all processes, sync, reboot).
74 Only the superuser may use this function.
76 The precise effect of the above actions depends on the architecture.
78 For the i386 architecture, the additional argument does not do anything
79 at present (2.1.122), but the type of reboot can be determined by ker‐
80 nel command line arguments (`reboot=...') to be either warm or cold,
81 and either hard or through the BIOS.
82
84 On success, zero is returned. On error, -1 is returned, and errno is
85 set appropriately.
86
88 EFAULT Problem with getting userspace data under
89 LINUX_REBOOT_CMD_RESTART2.
90 EINVAL Bad magic numbers or flag.
92 EPERM The calling process has insufficient privilege to call reboot();
94 the CAP_SYS_BOOT capability is required.
95
97 reboot() is Linux specific, and should not be used in programs intended
98 to be portable.
99
101 sync(2), bootparam(7), capabilities(7), ctrlaltdel(8), halt(8),
102 reboot(8)
103Linux 2.6.6 2004-05-27 REBOOT(2)