REBOOT(2) BSD System Calls Manual REBOOT(2)
reboot -- reboot system or halt processor
reboot() reboots the system. Only the superuser may reboot a machine on
demand. However, a reboot is invoked automatically in the event of unre-
coverable system failures.
howto is a mask of options; the system call interface allows the follow-
ing 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
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 abil-
ity 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
RB_HALT The processor is simply halted; no reboot takes place.
RB_POWERDOWN If used in conjunction with RB_HALT, and if the system
hardware supports the function, the system will be powered
RB_USERREQ By default, the system will halt if reboot() is called dur-
ing startup (before the system has finished autoconfigura-
tion), even if RB_HALT is not specified. This is because
panic(9)s during startup will probably just repeat on the
next boot. Use of this option implies that the user has
requested the action specified (for example, using the
ddb(4) boot reboot command), so the system will reboot if a
halt is not explicitly requested.
RB_INITNAME An option allowing the specification of an init program
(see init(8)) other than /sbin/init to be run when the sys-
tem 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 ddb(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 inter-
preted by the init(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 per-
formed (see fsck(8)).
If successful, this call never returns. Otherwise, a -1 is returned and
an error is returned in the global variable errno.
[EPERM] The caller is not the superuser.
ddb(4), crash(8), halt(8), init(8), reboot(8), savecore(8), boot(9),
The reboot() system call finally appeared in 4.0BSD.
Not all platforms support all possible arguments.
BSD April 29, 2017 BSD