reboot — reboot
system or halt processor
Standard C Library (libc, -lc)
The
reboot()
system call 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.
The howto argument 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- Normally the system only prompts the user if the loader specified root
file system has an error. This flag forces it to always prompt the user
for the root partition.
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_POWERCYCLE- After halting, the shutdown code will do what it can to turn off the power
and then turn the power back on. This requires hardware support, usually
an auxiliary microprocessor that can sequence the power supply. At present
only the ipmi(4) driver implements this feature.
RB_POWEROFF- After halting, the shutdown code will do what it can to turn off the
power. This requires hardware support.
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()
system 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_REROOT- Instead of rebooting, unmount all filesystems except the one containing
currently-running executable, and mount root filesystem using the same
mechanism which is used during normal boot, based on vfs.root.mountfrom
kenv(1) variable.
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
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 “kernel” 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)).
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.
The reboot() system call appeared in
4.0BSD.