table of contents
|REBOOT(2)||System Calls Manual||REBOOT(2)|
reboot system or halt processor
LIBRARY¶Standard C Library (libc, -lc)
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
<sys/reboot.h>, to be
passed to the new kernel or the new bootstrap and init programs.
- The default, causing the system to reboot in its usual fashion.
- 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)kernel”, where xx is the default disk name, without prompting for the file name.
- 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.)
- Dump kernel memory before rebooting; see savecore(8) for more information.
- The processor is simply halted; no reboot takes place. This option should be used with caution.
- After halting, the shutdown code will do what it can to turn off the power. This requires hardware support.
- 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.
- 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.
- 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.
- 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.
- Initially mount the root file system read-only. This is currently the default, and this option has been deprecated.
- Normally, the reboot procedure involves an automatic disk consistency
check and then multi-user operations.
RB_SINGLEprevents this, booting the system with a single-user shell on the console.
RB_SINGLEis 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)).
RETURN VALUES¶If successful, this call never returns. Otherwise, a -1 is returned and an error is returned in the global variable errno.
- The caller is not the super-user.
SEE ALSO¶crash(8), halt(8), init(8), reboot(8), savecore(8)
reboot() system call appeared in 4.0BSD.
|September 18, 2015||Linux 4.9.0-9-amd64|