bdea3adca6
RB_ASKNAME is no longer instructions to the boot loader to request a prompt for which kernel to boot. Instead, it asks for what the root file system to use. RB_INITNAME is unused, and never has been in FreeBSD as far as I can tell. Remove it from the documentation and fix comment. RB_SELFTEST and RB_MINIROOT likewise (though they were completely undocumented). These last three constants can likely just be deleted as nothing references them (even to set useless bits). RB_ASKNAME doesn't actually survive reboot, however, so needs to be communicated to the bootloader via other means. If the bootloader sets it, though, it will be honored.
165 lines
5.3 KiB
Groff
165 lines
5.3 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)reboot.2 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
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.Dd July 10, 2018
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.Dt REBOOT 2
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.Os
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.Sh NAME
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.Nm reboot
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.Nd reboot system or halt processor
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In unistd.h
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.In sys/reboot.h
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.Ft int
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.Fn reboot "int howto"
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.Sh DESCRIPTION
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The
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.Fn reboot
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system call
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reboots the system.
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Only the super-user may reboot a machine on demand.
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However, a reboot is invoked
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automatically in the event of unrecoverable system failures.
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.Pp
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The
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.Fa howto
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argument
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is a mask of options; the system call interface allows the following
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options, defined in the include file
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.In sys/reboot.h ,
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to be passed
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to the new kernel or the new bootstrap and init programs.
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.Bl -tag -width RB_POWERCYCLE
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.It Dv RB_AUTOBOOT
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The default, causing the system to reboot in its usual fashion.
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.It Dv RB_ASKNAME
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Normally the system only prompts the user if the loader specified root
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file system has an error.
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This flag forces it to always prompt the user for the root partition.
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.It Dv RB_DFLTROOT
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Use the compiled in root device.
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Normally, the system uses the device from which it was booted
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as the root device if possible.
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(The default behavior is dependent on the ability of the bootstrap program
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to determine the drive from which it was loaded, which is not possible
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on all systems.)
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.It Dv RB_DUMP
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Dump kernel memory before rebooting; see
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.Xr savecore 8
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for more information.
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.It Dv RB_HALT
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The processor is simply halted; no reboot takes place.
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This option should be used with caution.
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.It Dv RB_POWERCYCLE
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After halting, the shutdown code will do what it can to turn
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off the power and then turn the power back on.
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This requires hardware support, usually an auxiliary microprocessor
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that can sequence the power supply.
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At present only the
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.Xr ipmi 4
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driver implements this feature.
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.It Dv RB_POWEROFF
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After halting, the shutdown code will do what it can to turn
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off the power.
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This requires hardware support.
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.It Dv RB_KDB
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Load the symbol table and enable a built-in debugger in the system.
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This option will have no useful function if the kernel is not configured
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for debugging.
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Several other options have different meaning if combined
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with this option, although their use may not be possible
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via the
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.Fn reboot
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system call.
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See
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.Xr ddb 4
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for more information.
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.It Dv RB_NOSYNC
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Normally, the disks are sync'd (see
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.Xr sync 8 )
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before the processor is halted or rebooted.
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This option may be useful if file system changes have been made manually
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or if the processor is on fire.
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.It Dv RB_REROOT
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Instead of rebooting, unmount all filesystems except the one containing
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currently-running executable, and mount root filesystem using the same
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mechanism which is used during normal boot, based on
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vfs.root.mountfrom
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.Xr kenv 1
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variable.
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.It Dv RB_RDONLY
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Initially mount the root file system read-only.
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This is currently the default, and this option has been deprecated.
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.It Dv RB_SINGLE
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Normally, the reboot procedure involves an automatic disk consistency
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check and then multi-user operations.
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.Dv RB_SINGLE
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prevents this, booting the system with a single-user shell
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on the console.
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.Dv RB_SINGLE
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is actually interpreted by the
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.Xr init 8
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program in the newly booted system.
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.El
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.Pp
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When no options are given (i.e.,
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.Dv RB_AUTOBOOT
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is used), the system is
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rebooted from file
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.Dq kernel
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in the root file system of unit 0
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of a disk chosen in a processor specific way.
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An automatic consistency check of the disks is normally performed
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(see
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.Xr fsck 8 ) .
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.Sh RETURN VALUES
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If successful, this call never returns.
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Otherwise, a -1 is returned and an error is returned in the global
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variable
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.Va errno .
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.Sh ERRORS
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.Bl -tag -width Er
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.It Bq Er EPERM
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The caller is not the super-user.
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.El
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.Sh SEE ALSO
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.Xr crash 8 ,
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.Xr halt 8 ,
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.Xr init 8 ,
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.Xr reboot 8 ,
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.Xr savecore 8
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.Sh HISTORY
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The
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.Fn reboot
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system call appeared in
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.Bx 4.0 .
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