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REBOOT(2) NetBSD System Calls Manual REBOOT(2)
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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 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. 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 interpreted 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 information.
RB_HALT 0x0008 the processor is simply halted; no reboot takes
place. This option should be used with cau-
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 system. This option will have
no useful function if the kernel is not config-
ured 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 informa-
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 pro-
cessor 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 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 init(8) program in the newly
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 consistency 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 possible, 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 com-
piled 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.
NetBSD 9.0 September 4, 2009 NetBSD 9.0