REBOOT(2) System Calls Manual REBOOT(2)
NAME
reboot – reboot system or halt processor
SYNOPSIS
#include <unistd.h>
#include <sys/reboot.h>
int
reboot(int howto);
DESCRIPTION
reboot() reboots the system. Only the super-user may reboot a machine on
demand. However, a reboot may be invoked automatically in the event of
unrecoverable system failures. Programs other than reboot(8) should not
call reboot(). Shutdown(8) or a higher-level API will shut the system
down cleanly.
Howto is a mask of options; the system call interface allows the
following options, defined in the include file ⟨sys/reboot.h⟩, to be
passed to the new kernel or the new bootstrap and init programs.
RB_AUTOBOOT The default, causing the system to reboot in its usual
fashion.
RB_ASKNAME Interpreted by the bootstrap program itself, causing it to
prompt on the console as to what file should be booted.
Normally, the system is booted from the file “xx(0,0)bsd”,
where xx is the default disk name, without prompting for
the file name.
RB_DFLTROOT Use the compiled in root device. Normally, the system uses
the device from which it was booted as the root device if
possible. (The default behavior is dependent on the
ability of the bootstrap program to determine the drive
from which it was loaded, which is not possible on all
systems.)
RB_DUMP Dump kernel memory before rebooting; see savecore(8) for
more information.
RB_HALT the processor is simply halted; no reboot takes place.
This option should be used with caution.
RB_INITNAME An option allowing the specification of an init program
(see launchd(8)) other than /sbin/launchd to be run when
the system reboots. This switch is not currently
available.
RB_KDB Load the symbol table and enable a built-in debugger in the
system. This option will have no useful function if the
kernel is not configured for debugging. Several other
options have different meaning if combined with this
option, although their use may not be possible via the
reboot() call. See kadb(4) for more information.
RB_NOSYNC Normally, the disks are sync'd (see sync(8)) before the
processor is halted or rebooted. This option may be useful
if file system changes have been made manually or if the
processor is on fire.
RB_RDONLY Initially mount the root file system read-only. This is
currently the default, and this option has been deprecated.
RB_SINGLE Normally, the reboot procedure involves an automatic disk
consistency check and then multi-user operations.
RB_SINGLE prevents this, booting the system with a single-
user shell on the console. RB_SINGLE is actually
interpreted by the launchd(8) program in the newly booted
system.
When no options are given (i.e., RB_AUTOBOOT is used), the
system is rebooted from file ``bsd'' in the root file
system of unit 0 of a disk chosen in a processor specific
way. An automatic consistency check of the disks is
normally performed (see fsck(8)).
RETURN VALUES
If successful, this call never returns. Otherwise, a -1 is returned and
an error is returned in the global variable errno.
ERRORS
[EPERM] The caller is not the super-user.
SEE ALSO
shutdown(8), halt(8), launchd(8), reboot(8)
BUGS
The HP300 implementation supports neither RB_DFLTROOT nor RB_KDB.
HISTORY
The reboot() function call appeared in 4.0BSD.
BSD 4 June 4, 1993 BSD 4