REBOOT(2) BSD System Calls Manual REBOOT(2)
reboot -- reboot system or halt processor
Standard C Library (libc, -lc)
reboot(int howto, char *bootstr);
reboot() reboots the system. Only the super-user may reboot a machine on demand. However,
a reboot is invoked automatically in the event of unrecoverable system failures.
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. In addition to the options described below, other options described in
boothowto(9) may be set, but such options may be ignored by the system.
Options can be combined together by OR'ing them, eg. RB_DUMP | RB_NOSYNC would be inter-
preted as ``dump kernel memory before rebooting and don't sync the disks''.
RB_AUTOBOOT 0x0000 The default, causing the system to reboot in its usual fashion.
RB_ASKNAME 0x0001 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)netbsd'', where xx is the
default disk name, without prompting for the file name.
RB_DUMP 0x0100 Dump kernel memory before rebooting; see savecore(8) for more
RB_HALT 0x0008 the processor is simply halted; no reboot takes place. This
option should be used with caution.
RB_POWERDOWN 0x0808 This option is always used in conjunction with RB_HALT, and if the
system hardware supports the function, the system will be powered
off, otherwise it has no effect.
RB_INITNAME 0x0010 An option allowing the specification of an init program (see
init(8)) other than /sbin/init to be run when the system reboots.
This switch is not currently available.
RB_KDB 0x0040 Load the symbol table and enable a built-in debugger in the sys-
tem. This option will have no useful function if the kernel is
not configured for debugging. Several other options have differ-
ent meaning if combined with this option, although their use may
not be possible via the reboot() call. See ddb(4) for more infor-
RB_NOSYNC 0x0004 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 0x0080 Initially mount the root file system read-only. This is currently
the default, and this option has been deprecated.
RB_SINGLE 0x0002 Normally, the reboot procedure involves an automatic disk consis-
tency 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 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 ``netbsd'' in the root file system of unit 0
of a disk chosen in a processor specific way. An automatic con-
sistency check of the disks is normally performed (see fsck(8)).
RB_STRING 0x0400 bootstr is a string passed to the firmware on the machine, if pos-
sible, if this option is set. Currently this is only implemented
on the sparc and the sun3 ports.
RB_USERCONF 0x1000 Initially invoke the userconf(4) facility when the system starts
up again, if it has been compiled into the kernel that is loaded.
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 super-user.
ddb(4), crash(8), halt(8), init(8), reboot(8), savecore(8), boothowto(9)
The reboot() function call appeared in 4.0BSD.
The RB_DFLTROOT option is now obsolete.
BSD September 4, 2009 BSD