REBOOT(2) | System Calls Manual | REBOOT(2)

# NAME

`reboot` —
reboot system or halt processor

# LIBRARY

Standard C Library (libc, -lc)

# SYNOPSIS

`#include <unistd.h>`
`#include <sys/reboot.h>`

int
`reboot`(int howto, char *bootstr);

# DESCRIPTION

`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 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 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 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` | `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 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 ``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 compiled into the kernel that is loaded.

# RETURN VALUES

If successful, this call never returns. Otherwise, a -1 is returned and an error is returned in the global variable errno.

# ERRORS

[`EPERM`]
  The caller is not the super-user.

# SEE ALSO

ddb(4), crash(8), halt(8), init(8), reboot(8), savecore(8), boothowto(9)

# HISTORY

The `reboot`() function call appeared in 4.0BSD.

The `RB_DFLTROOT` option is now obsolete.

September 4, 2009 | NetBSD 9.3