The reboot call reboots the system, or enables/disables the reboot
keystroke (abbreviated CAD, since the default is Ctrl-Alt-Delete; it can be
changed using loadkeys(1)).
This system call will fail (with EINVAL) unless magic equals
LINUX_REBOOT_MAGIC1 (that is, 0xfee1dead) and magic2 equals
LINUX_REBOOT_MAGIC2 (that is, 672274793). However, since 2.1.17 also
LINUX_REBOOT_MAGIC2A (that is, 85072278) and since 2.1.97 also
LINUX_REBOOT_MAGIC2B (that is, 369367448) and since 2.5.71 also
LINUX_REBOOT_MAGIC2C (that is, 537993216) are permitted as value for
magic2. (The hexadecimal values of these constants are meaningful.) The
flag argument can have the following values:
(RB_AUTOBOOT, 0x1234567). The message `Restarting system.'
is printed, and a default restart is performed immediately. If not
preceded by a sync(2), data will be lost.
(RB_HALT_SYSTEM, 0xcdef0123; since 1.1.76). The message
`System halted.' is printed, and the system is halted. Control is given to
the ROM monitor, if there is one. If not preceded by a sync(2),
data will be lost.
(0x4321fedc; since 2.1.30). The message `Power down.' is
printed, the system is stopped, and all power is removed from the system,
if possible. If not preceded by a sync(2), data will be lost.
(0xa1b2c3d4; since 2.1.30). The message `Restarting system
with command '%s'' is printed, and a restart (using the command string
given in arg) is performed immediately. If not preceded by a
sync(2), data will be lost.
(RB_ENABLE_CAD, 0x89abcdef). CAD is enabled. This means
that the CAD keystroke will immediately cause the action associated to
(RB_DISABLE_CAD, 0). CAD is disabled. This means that the
CAD keystroke will cause a SIGINT signal to be sent to init (process 1),
whereupon this process may decide upon a proper action (maybe: kill all
processes, sync, reboot).
Only the super-user may use this function.
The precise effect of the above actions depends on the architecture. For the
i386 architecture, the additional argument does not do anything at present
(2.1.122), but the type of reboot can be determined by kernel command line
arguments (`reboot=...') to be either warm or cold, and either hard or through