52501c5ede
- Document better what the -C option means. - The -c option is currently a no-op. - The -D and -h options do not allow switching between single/dual console modes and internal/video consoles. (This used to be true for the old biosdisk boot code, but now they just force the multiple consoles mode and serial console, respectively.)
360 lines
9.8 KiB
Groff
360 lines
9.8 KiB
Groff
.\" Copyright (c) 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software written and contributed
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.\" to Berkeley by William Jolitz.
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.\"
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.\" Almost completely rewritten for FreeBSD 2.1 by Joerg Wunsch.
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.\"
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.\" Substantially revised for FreeBSD 3.1 by Robert Nordier.
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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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.\" 4. 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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.\" @(#)boot_i386.8 8.2 (Berkeley) 4/19/94
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.\"
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.\" $FreeBSD$
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.\"
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.Dd September 30, 2004
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.Dt BOOT 8 i386
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.Os
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.Sh NAME
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.Nm boot
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.Nd system bootstrapping procedures
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.Sh DESCRIPTION
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.Sy Power fail and crash recovery .
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Normally, the system will reboot itself at power-up or after crashes.
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An automatic consistency check of the file systems will be performed,
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and unless this fails, the system will resume multi-user operations.
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.Pp
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.Sy Cold starts .
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Most i386 PCs attempt to boot first from floppy disk drive 0 (sometimes
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known as drive A:) and, failing that, from hard disk drive 0 (sometimes
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known as drive C:, or as drive 0x80 to the BIOS).
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Some BIOSes allow
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you to change this default sequence, and may also include a CD-ROM
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drive as a boot device.
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.Pp
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By default, a three-stage bootstrap is employed, and control is
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automatically passed from the boot blocks (bootstrap stages one and
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two) to a separate third-stage bootstrap program,
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.Xr loader 8 .
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This third stage provides more sophisticated control over the booting
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process than it is possible to achieve in the boot blocks, which are
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constrained by occupying limited fixed space on a given disk or slice.
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.Pp
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However, it is possible to dispense with the third stage altogether,
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either by specifying a kernel name in the boot block parameter
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file,
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.Pa /boot.config ,
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or, unless option
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.Fl n
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is set, by hitting a key during a brief pause (while one of the characters
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.Sy - ,
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.Sy \e ,
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.Sy \&| ,
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or
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.Sy /
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is displayed) before
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.Xr loader 8
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is invoked.
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Booting will also be attempted at stage two, if the
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third stage cannot be loaded.
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.Pp
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Make note of the fact that
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.Pa /boot.config
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is read only from the
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.Ql a
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partition. As a result, slices which are missing an
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.Ql a
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parition require user intervention during the boot process.
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.Pp
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The remainder of this subsection deals only with the boot blocks.
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The
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.Xr loader 8
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program is documented separately.
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.Pp
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After the boot blocks have been loaded,
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you should see a prompt similar to the following:
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.Bd -literal
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>> FreeBSD/i386 BOOT
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Default: 0:ad(0,a)/boot/loader
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boot:
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.Ed
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.Pp
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The automatic boot will attempt to load
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.Pa /boot/loader
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from partition
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.Ql a
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of either the floppy or the hard disk.
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This boot may be aborted by typing any character on the keyboard
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at the
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.Ql boot:
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prompt.
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At this time, the following input will be accepted:
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.Bl -tag -width indent
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.It Ic \&?
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Give a short listing of the files in the root directory of the default
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boot device, as a hint about available boot files.
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(A
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.Ic ?\&
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may also be specified as the last segment of a path, in which case
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the listing will be of the relevant subdirectory.)
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.Pp
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.It Xo
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.Sm off
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.Ar bios_drive : interface ( unit , Oo Ar slice , Oc Ar part )
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.Sm on
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.Ar filename
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.Op Fl aCcDdghmnPprsv
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.Xc
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Specify boot file and flags.
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.Bl -tag -width indent
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.It Ar bios_drive
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The drive number as recognized by the BIOS.
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0 for the first drive, 1 for the second drive, etc.
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.It Ar interface
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The type of controller to boot from.
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Note that the controller is required
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to have BIOS support since the BIOS services are used to load the
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boot file image.
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.Pp
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The supported interfaces are:
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.Pp
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.Bl -tag -width "adXX" -compact
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.It ad
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ST506, IDE, ESDI, RLL disks on a WD100[2367] or lookalike
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controller
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.It fd
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5 1/4" or 3 1/2" High density floppies
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.It da
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SCSI disk on any supported SCSI controller
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.\".It cd
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.\"boot from CDROM
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.El
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.It Ar unit
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The unit number of the drive on the interface being used.
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0 for the first drive, 1 for the second drive, etc.
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.It Oo Ar slice , Oc Ns Ar part
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The partition letter inside the
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.Bx
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portion of the disk.
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See
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.Xr bsdlabel 8 .
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By convention, only partition
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.Ql a
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contains a bootable image.
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If sliced disks are used
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.Pq Dq fdisk partitions ,
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any
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.Ar slice
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(1 for the first slice, 2 for the second slice, etc.\&)
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can be booted from, with the default (if not specified) being the active slice
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or, otherwise, the first
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.Fx
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slice.
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If
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.Ar slice
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is specified as 0, the first
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.Fx
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slice (also known as
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.Dq compatibility
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slice) is booted from.
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.It Ar filename
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The pathname of the file to boot (relative to the root directory
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on the specified partition).
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Defaults to
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.Pa /kernel .
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Symbolic links are not supported (hard links are).
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.It Fl aCcDdghmnPprsv
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Boot flags:
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.Pp
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.Bl -tag -width "-CXX" -compact
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.It Fl a
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during kernel initialization,
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ask for the device to mount as the root file system.
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.It Fl C
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try to mount root file system from a CD-ROM.
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.It Fl c
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this flag is currently a no-op.
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.It Fl D
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boot with the dual console configuration.
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In the single
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configuration, the console will be either the internal display
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or the serial port, depending on the state of the
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.Fl h
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option below.
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In the dual console configuration,
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both the internal display and the serial port will become the console
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at the same time, regardless of the state of the
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.Fl h
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option.
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.It Fl d
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enter the DDB kernel debugger
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(see
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.Xr ddb 4 )
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as early as possible in kernel initialization.
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.It Fl g
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use the GDB remote debugging protocol.
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.It Fl h
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force the serial console.
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For instance, if you boot from the internal console,
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you can use the
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.Fl h
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option to force the kernel to use the serial port as its
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console device.
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The serial port driver
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.Xr sio 4
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has a flag (0x20) to override this option.
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If that flag is set, the serial port will always be used as the console,
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regardless of the
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.Fl h
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option described here.
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See the man page for
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.Xr sio 4
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for more details.
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.It Fl m
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mute the console.
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.It Fl n
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ignore key press to interrupt boot before
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.Xr loader 8
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is invoked.
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.It Fl P
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probe the keyboard.
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If no keyboard is found, the
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.Fl D
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and
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.Fl h
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options are automatically set.
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.It Fl p
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pause after each attached device during the device probing phase.
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.It Fl r
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use the statically configured default for the device containing the
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root file system
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(see
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.Xr config 8 ) .
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Normally, the root file system is on the device
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that the kernel was loaded from.
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.It Fl s
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boot into single-user mode; if the console is marked as
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.Dq insecure
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(see
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.Xr ttys 5 ) ,
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the root password must be entered.
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.It Fl v
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be verbose during device probing (and later).
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.El
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.El
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.El
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.Pp
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You may put a BIOS drive number, a controller type, a unit number,
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a partition, a kernel file name, and any valid option in
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.Pa /boot.config
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to set defaults.
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Enter them in one line just as you type at the
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.Ql boot:
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prompt.
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.Sh FILES
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.Bl -tag -width /boot/loader -compact
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.It Pa /boot.config
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parameters for the boot blocks (optional)
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.It Pa /boot/boot1
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first stage bootstrap file
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.It Pa /boot/boot2
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second stage bootstrap file
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.It Pa /boot/loader
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third stage bootstrap
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.It Pa /boot/kernel/kernel
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default kernel
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.It Pa /boot/kernel.old/kernel
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typical non-default kernel (optional)
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.El
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.Sh SEE ALSO
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.Xr ddb 4 ,
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.Xr ttys 5 ,
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.Xr boot0cfg 8 ,
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.Xr bsdlabel 8 ,
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.Xr btxld 8 ,
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.Xr config 8 ,
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.Xr halt 8 ,
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.Xr loader 8 ,
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.Xr reboot 8 ,
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.Xr shutdown 8
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.Sh DIAGNOSTICS
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When disk-related errors occur, these are reported by the second-stage
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bootstrap using the same error codes returned by the BIOS, for example
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.Dq Disk error 0x1 (lba=0x12345678) .
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Here is a partial list of these error codes:
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.Pp
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.Bl -tag -width "0x80" -compact
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.It 0x1
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Invalid argument
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.It 0x2
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Address mark not found
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.It 0x4
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Sector not found
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.It 0x8
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DMA overrun
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.It 0x9
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DMA attempt across 64K boundary
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.It 0xc
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Invalid media
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.It 0x10
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Uncorrectable CRC/ECC error
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.It 0x20
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Controller failure
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.It 0x40
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Seek failed
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.It 0x80
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Timeout
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.El
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.Pp
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.Sy "NOTE" :
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On older machines, or otherwise where EDD support (disk packet
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interface support) is not available, all boot-related files and
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structures (including the kernel) that need to be accessed during the
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boot phase must reside on the disk at or below cylinder 1023 (as the
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BIOS understands the geometry).
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When a
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.Dq Disk error 0x1
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is reported by the second-stage bootstrap, it generally means that this
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requirement has not been adhered to.
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.Sh BUGS
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The
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.Xr bsdlabel 5
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format used by this version of
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.Bx
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is quite
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different from that of other architectures.
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.Pp
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Due to space constraints, the keyboard probe initiated by the
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.Fl P
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option is simply a test that the BIOS has detected an
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.Dq extended
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keyboard.
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If an
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.Dq XT/AT
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keyboard (with no F11 and F12 keys, etc.) is attached, the probe will
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fail.
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