358 lines
9.7 KiB
Groff
358 lines
9.7 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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.\" 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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.\" @(#)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 July 11, 2020
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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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Some newer PCs boot using UEFI firmware, not BIOS.
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That process is described
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in
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.Xr uefi 8 .
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.Pp
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A three-stage bootstrap is employed.
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Control is passed from the boot blocks (bootstrap stages one and two) to a
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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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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/x86 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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.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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.Ar filename
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.Sm on
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.Op Fl aCcDdghmnPprsv
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.Op Fl S Ns Ar speed
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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 /boot/kernel/kernel .
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Symbolic links are not supported (hard links are).
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.It Xo Op Fl aCcDdghmnPpqrsv
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.Op Fl S Ns Ar speed
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.Xc
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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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.It Fl m
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mute the console to suppress all kernel console input and output during the
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boot.
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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 q
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be quiet,
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do not write anything to the console unless automatic boot fails or
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is disabled.
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This option only affects second-stage bootstrap,
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to prevent next stages from writing to the console use in
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combination with the
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.Fl m
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option.
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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 S Ns Ar speed
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set the speed of the serial console to
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.Ar speed .
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The default is 9600 unless it has been overridden by setting
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.Va BOOT_COMCONSOLE_SPEED
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in
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.Xr make.conf 5
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and recompiling and reinstalling the boot blocks.
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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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Use the
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.Pa /boot.config
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file to set the default configuration options for the boot block code.
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See
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.Xr boot.config 5
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for more information about the
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.Pa /boot.config
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file.
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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 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 SEE ALSO
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.Xr ddb 4 ,
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.Xr boot.config 5 ,
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.Xr make.conf 5 ,
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.Xr mount.conf 5 ,
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.Xr ttys 5 ,
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.Xr boot0cfg 8 ,
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.Xr btxld 8 ,
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.Xr config 8 ,
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.Xr efibootmgr 8 ,
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.Xr efivar 8 ,
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.Xr gpart 8 ,
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.Xr gptboot 8 ,
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.Xr gptzfsboot 8 ,
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.Xr halt 8 ,
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.Xr loader 8 ,
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.Xr nextboot 8 ,
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.Xr reboot 8 ,
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.Xr shutdown 8 ,
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.Xr uefi 8 ,
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.Xr zfsbootcfg 8
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.Sh BUGS
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The bsdlabel 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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