976 lines
23 KiB
Groff
976 lines
23 KiB
Groff
.\" Copyright (c) 1987, 1988, 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 contributed to Berkeley by
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.\" Symmetric Computer Systems.
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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. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgment:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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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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.\" @(#)disklabel.8 8.2 (Berkeley) 4/19/94
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.\" $FreeBSD$
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.\"
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.Dd March 15, 2003
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.Dt DISKLABEL 8
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.Os
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.Sh NAME
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.Nm disklabel
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.Nd read and write disk pack label
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.Sh SYNOPSIS
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.Nm
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.Op Fl r
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.Ar disk
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.Nm
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.Fl w
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.Op Fl nr
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.Op Fl m Ar machine
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.Ar disk type
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.Op Ar packid
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.Nm
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.Fl e
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.Op Fl nr
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.Op Fl m Ar machine
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.Ar disk
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.Nm
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.Fl R
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.Op Fl nr
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.Op Fl m Ar machine
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.Ar disk protofile
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.Pp
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.Nm
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.Fl B
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.Op Fl b Ar boot
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.Op Fl m Ar machine
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.Ar disk
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.Nm
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.Fl w B
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.Op Fl n
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.Op Fl b Ar boot
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.Op Fl m Ar machine
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.Ar disk type
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.Op Ar packid
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.Nm
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.Fl R B
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.Op Fl n
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.Op Fl b Ar boot
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.Op Fl m Ar machine
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.Ar disk protofile
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.Sh DESCRIPTION
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The
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.Nm
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utility
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installs, examines or modifies the label on a disk drive or pack.
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When writing
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the label, it can be used to change the drive identification, the disk
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partitions on the drive, or to replace a damaged label.
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There are several forms
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of the command that read (display), install, or edit the label on a disk.
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In addition,
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.Nm
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can install bootstrap code.
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.Ss Raw or In-Core Label
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The disk label resides close to or at the beginning of each disk slice.
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For faster access, the kernel maintains a copy in core at all times.
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By default, most
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.Nm
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access the in-core copy of the label.
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To access the raw (on-disk) copy, use the
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.Fl r
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option.
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This option allows a label to be installed on a disk without kernel
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support for a label, such as when labels are first installed on a system; it
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must be used when first installing a label on a disk.
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The specific effect of
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.Fl r
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is described under each command.
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.Ss Disk Device Name
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All
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.Nm
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forms require a disk device name, which should always be the raw
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device name representing the disk or slice.
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For example,
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.Pa da0
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represents the entire disk regardless of any
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.Tn DOS
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partitioning,
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and
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.Pa da0s1
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represents a slice.
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Some devices, most notably
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.Xr ccd 4 ,
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require that the
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.Dq whole-disk
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(or
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.Ql c )
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partition be specified.
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For example,
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.Pa ccd0c .
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When specifying the device,
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the
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.Pa /dev/
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path prefix may be omitted;
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the
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.Nm
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utility will automatically prepend it.
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.Ss Reading the Disk Label
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To examine the label on a disk drive, use
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.Nm
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without options:
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.Pp
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.Nm
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.Op Fl r
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.Ar disk
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.Pp
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.Ar disk
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represents the raw disk in question, and may be in the form
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.Pa da0
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or
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.Pa /dev/da0c .
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It will display all of the parameters associated with the drive and its
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partition layout.
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Unless the
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.Fl r
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option is given,
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the kernel's in-core copy of the label is displayed;
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if the disk has no label, or the partition types on the disk are incorrect,
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the kernel may have constructed or modified the label.
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If the
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.Fl r
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option is given,
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.Nm
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reads the label from the raw disk and displays it.
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Both versions are usually
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identical except in the case where a label has not yet been initialized or
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is corrupt.
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.Ss Writing a Standard Label
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To write a standard label, use the form
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.Pp
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.Nm
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.Fl w
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.Op Fl nr
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.Op Fl m Ar machine
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.Ar disk type
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.Op Ar packid
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.Pp
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The required arguments to
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.Nm
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are the drive to be labeled, and the drive type as described in the
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.Xr disktab 5
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file.
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The drive parameters and partitions are taken from that file.
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If different disks of the same physical type are to have different partitions,
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it will be necessary to have separate
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.Xr disktab 5
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entries describing each, or to edit
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the label after installation as described below.
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The optional argument is a
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pack identification string, up to 16 characters long.
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The
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.Ar packid
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must be quoted if it contains blanks.
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.Pp
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If the
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.Fl m
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option is given, then label will be written so that
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it is understood by the target
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.Ar machine ;
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defaults to the current hardware architecture.
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.Pp
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If
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.Fl n
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is used, no data will be written to the device, and instead the
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disk label that would have been written will be printed to standard output.
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.Pp
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If the
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.Fl r
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option is given, the disk sectors containing the label and bootstrap
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will be written directly.
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A side-effect of this is that any existing bootstrap code will be overwritten
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and the disk rendered unbootable.
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See the boot options below for a method of
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writing the and the bootstrap at the same time.
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If
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.Fl r
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is not specified,
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the existing label will be updated via the in-core copy, and any bootstrap
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code will be unaffected.
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|
If the disk does not already have a label, the
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.Fl r
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option must be used.
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In either case, the kernel's in-core label is replaced.
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.Pp
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|
For a virgin disk that is not known to
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.Xr disktab 5 ,
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|
.Ar type
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can be specified as
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|
.Cm auto .
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|
In this case, the driver is requested to produce a virgin label for the
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disk.
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|
This might or might not be successful, depending on whether the
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driver for the disk is able to get the required data without reading
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anything from the disk at all.
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|
It will likely succeed for all
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.Tn SCSI
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disks, most
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|
.Tn IDE
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|
disks, and
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|
.Cm vnode
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type memory disks
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.Pq Xr md 4 .
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|
Writing a label to the
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|
disk is the only supported operation, and the
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|
.Ar disk
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|
itself must be provided as the canonical name, i.e., not as a full
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path name.
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.Pp
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For most harddisks, a label based on percentages for most partitions (and
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|
one partition with a size of
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|
.Ql * )
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|
will produce a reasonable configuration.
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|
.Pp
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|
PC-based systems have special requirements in order for the
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|
.Tn BIOS
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|
to properly recognize a
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.Fx
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|
disk label.
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|
Older systems may require what is known as a
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|
.Dq dangerously-dedicated
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|
disk label, which creates a fake
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|
.Tn DOS
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|
partition to work around problems older
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|
.Tn BIOS Ns es
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have with modern disk geometries.
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|
On newer systems, a normal
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|
.Tn DOS
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|
partition should generally be created using
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|
.Xr fdisk 8 ,
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|
and then a
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|
.Fx
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|
disk label within that slice.
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|
This is described later on in this page.
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|
.Pp
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|
Installing a new disk label does not in of itself allow the system to boot
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a kernel using that label.
|
|
Boot blocks must also be installed, which is
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|
described later on in this manual page.
|
|
.Ss Editing an Existing Disk Label
|
|
To edit an existing disk label, use the form
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|
.Pp
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|
.Nm
|
|
.Fl e
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|
.Op Fl nr
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.Op Fl m Ar machine
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|
.Ar disk
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|
.Pp
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|
This command reads the label from the in-core kernel copy, or directly from the
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|
disk if the
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|
.Fl r
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|
option is also specified.
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|
The label is written to a file in
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|
.Tn ASCII
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|
format, and then supplied to an editor for changes.
|
|
If no editor is specified in the
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|
.Ev EDITOR
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|
environment variable,
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|
.Xr vi 1
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|
is used.
|
|
When the editor terminates, the label file is used to rewrite the disk label.
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|
Existing bootstrap code is unchanged regardless of whether
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|
.Fl r
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|
was specified.
|
|
.Pp
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|
If the
|
|
.Fl m
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|
option is given, then the label will be written so that
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|
it is understood by the target
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|
.Ar machine ;
|
|
defaults to the current hardware architecture.
|
|
.Pp
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|
If
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|
.Fl n
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|
is used, no data will be written to the device, and instead the
|
|
disk label that would have been written will be printed to standard output.
|
|
This is
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|
useful to see how a partitioning scheme will work out for a specific disk.
|
|
.Ss Restoring a Disk Label From a File
|
|
To restore a disk label from a file, use the form
|
|
.Pp
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|
.Nm
|
|
.Fl R
|
|
.Op Fl nr
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|
.Op Fl m Ar machine
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|
.Ar disk protofile
|
|
.Pp
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|
.Nm
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|
is capable of restoring a disk label that was previously saved in a file in
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|
.Tn ASCII
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|
format.
|
|
The prototype file used to create the label should be in the same format as that
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|
produced when reading or editing a label.
|
|
Comments are delimited by
|
|
.Ql #
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|
and newline.
|
|
As when writing a new label, any existing bootstrap code will be
|
|
clobbered if
|
|
.Fl r
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|
is specified, and will be unaffected otherwise.
|
|
See the boot options below for a
|
|
method of restoring the label and writing the bootstrap at the same time.
|
|
.Pp
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|
If the
|
|
.Fl m
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|
option is given, then the label will be written so that
|
|
it is understood by the target
|
|
.Ar machine ;
|
|
defaults to the current hardware architecture.
|
|
.Pp
|
|
If
|
|
.Fl n
|
|
is used, no data will be written to the device, and instead the
|
|
disk label that would have been written will be printed to standard output.
|
|
This is
|
|
useful to see how a partitioning scheme will work out for a specific disk.
|
|
.Ss Installing Bootstraps
|
|
The final three forms of
|
|
.Nm
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|
are used to install bootstrap code.
|
|
If a
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|
.Dq dangerously-dedicated
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|
disk is created for compatibility with older PC systems,
|
|
the raw disk name such as
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|
.Pa da0
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|
should be specified.
|
|
If an existing slice should be labeled,
|
|
the slice name such as
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|
.Pa da0s1
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|
should be specified,
|
|
and to make it bootable,
|
|
.Tn MBR
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|
on the base disk should probably be updated; see
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|
.Xr fdisk 8 .
|
|
.Pp
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|
.Nm
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|
.Fl B
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|
.Op Fl b Ar boot
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|
.Op Fl m Ar machine
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|
.Ar disk
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|
.Pp
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|
This form installs the bootstrap only.
|
|
It does not change the disk label.
|
|
Never use this command on a base disk, such as
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|
.Pa da0 ,
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|
unless the intent is to create a
|
|
.Dq dangerously-dedicated
|
|
disk.
|
|
This command is typically run on a slice such as
|
|
.Pa da0s1 .
|
|
.Pp
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|
The
|
|
.Fl m
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|
option should be specified if the label was
|
|
created for a different hardware architecture,
|
|
.Ar machine .
|
|
.Pp
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|
.Nm
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|
.Fl w B
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|
.Op Fl n
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|
.Op Fl b Ar boot
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|
.Op Fl m Ar machine
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|
.Ar disk type
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|
.Op Ar packid
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|
.Pp
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|
This form corresponds to the
|
|
.Dq "write label"
|
|
command described above.
|
|
In addition to writing a new volume label, it also installs the bootstrap.
|
|
If run on a base disk, this command will create a
|
|
.Dq dangerously-dedicated
|
|
label.
|
|
This command is normally run on a slice rather than a base disk.
|
|
.Pp
|
|
If the
|
|
.Fl m
|
|
option is given, then the label and bootstrap will be written so that
|
|
they are understood by the target
|
|
.Ar machine ;
|
|
defaults to the current hardware architecture.
|
|
.Pp
|
|
If
|
|
.Fl n
|
|
is used, no data will be written to the device, and instead the
|
|
disk label that would have been written will be printed to standard output.
|
|
.Pp
|
|
.Nm
|
|
.Fl R B
|
|
.Op Fl n
|
|
.Op Fl b Ar boot
|
|
.Op Fl m Ar machine
|
|
.Ar disk protofile
|
|
.Pp
|
|
This form corresponds to the
|
|
.Dq "restore label"
|
|
command described above.
|
|
In addition to restoring the volume label, it also installs the bootstrap.
|
|
If run on a base disk, this command will create a
|
|
.Dq dangerously-dedicated
|
|
label.
|
|
This command is normally run on a slice rather than a base disk.
|
|
.Pp
|
|
The bootstrap commands always access the disk directly, so it is not necessary
|
|
to specify the
|
|
.Fl r
|
|
option.
|
|
.Pp
|
|
If the
|
|
.Fl m
|
|
option is given, then the label and bootstrap will be written so that
|
|
they are understood by the target
|
|
.Ar machine ;
|
|
defaults to the current hardware architecture.
|
|
.Pp
|
|
If
|
|
.Fl n
|
|
is used, no data will be written to the device, and instead the
|
|
disk label that would have been written will be printed to standard output.
|
|
.Pp
|
|
The bootstrap code is comprised of two boot programs compiled into a single
|
|
.Pa /boot/boot
|
|
image.
|
|
An alternative boot image may be specified with the
|
|
.Fl b
|
|
option.
|
|
.Ss Initializing/Formatting a Bootable Disk From Scratch
|
|
To initialize a disk from scratch, the following sequence is recommended.
|
|
Please note that this will wipe everything that was previously on the disk,
|
|
including any
|
|
.No non- Ns Fx
|
|
slices.
|
|
.Bl -enum
|
|
.It
|
|
Use
|
|
.Xr fdisk 8
|
|
to initialize the hard disk, and create a slice table, referred to
|
|
as the
|
|
.Dq "partition table"
|
|
in
|
|
.Tn DOS .
|
|
.It
|
|
Use
|
|
.Nm
|
|
to define partitions on
|
|
.Fx
|
|
slices created in the previous step.
|
|
.It
|
|
Finally use
|
|
.Xr newfs 8
|
|
to create file systems on new partitions.
|
|
.El
|
|
.Pp
|
|
A typical partitioning scheme would be to have an
|
|
.Ql a
|
|
partition
|
|
of approximately 128MB to hold the root file system, a
|
|
.Ql b
|
|
partition for
|
|
swap, a
|
|
.Ql d
|
|
partition for
|
|
.Pa /var
|
|
(usually 128MB), an
|
|
.Ql e
|
|
partition
|
|
for
|
|
.Pa /var/tmp
|
|
(usually 128MB), an
|
|
.Ql f
|
|
partition for
|
|
.Pa /usr
|
|
(usually around 2GB),
|
|
and finally a
|
|
.Ql g
|
|
partition for
|
|
.Pa /home
|
|
(usually all remaining space).
|
|
Your mileage may vary.
|
|
.Pp
|
|
.Nm fdisk Fl BI Pa da0
|
|
.Pp
|
|
.Nm
|
|
.Fl w B
|
|
.Pa da0s1
|
|
.Cm auto
|
|
.Pp
|
|
.Nm
|
|
.Fl e
|
|
.Pa da0s1
|
|
.Sh FILES
|
|
.Bl -tag -width ".Pa /etc/disktab" -compact
|
|
.It Pa /boot/boot
|
|
Default boot image.
|
|
.It Pa /etc/disktab
|
|
Disk description file.
|
|
.El
|
|
.Sh SAVED FILE FORMAT
|
|
The
|
|
.Nm
|
|
utility
|
|
uses an
|
|
.Tn ASCII
|
|
version of the label when examining, editing, or restoring a disk
|
|
label.
|
|
The format is:
|
|
.Bd -literal -offset 4n
|
|
# /dev/da1c:
|
|
type: SCSI
|
|
disk: da0s1
|
|
label:
|
|
flags:
|
|
bytes/sector: 512
|
|
sectors/track: 51
|
|
tracks/cylinder: 19
|
|
sectors/cylinder: 969
|
|
cylinders: 1211
|
|
sectors/unit: 1173930
|
|
rpm: 3600
|
|
interleave: 1
|
|
trackskew: 0
|
|
cylinderskew: 0
|
|
headswitch: 0 # milliseconds
|
|
track-to-track seek: 0 # milliseconds
|
|
drivedata: 0
|
|
|
|
8 partitions:
|
|
# size offset fstype [fsize bsize bps/cpg]
|
|
a: 81920 0 4.2BSD 1024 8192 16 # (Cyl. 0 - 84*)
|
|
b: 160000 81920 swap # (Cyl. 84* - 218*)
|
|
c: 1173930 0 unused 0 0 # (Cyl. 0 - 1211*)
|
|
h: 962010 211920 vinum # (Cyl. 218*- 1211*)
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.Ed
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.Pp
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Lines starting with a
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.Ql #
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mark are comments.
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Most of the other specifications are no longer used.
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The ones which must still be set correctly are:
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.Pp
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.Bl -inset
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.It Ar label
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is an optional label, set by the
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.Ar packid
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option when writing a label.
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.It Ar flags
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may be
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.Cm removable , ecc
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or
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.Cm badsect .
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.Cm removable
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is set for removable media drives, but no current
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.Fx
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driver evaluates this
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flag.
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.Cm ecc
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is no longer supported;
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.Cm badsect
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specifies that the drive can perform bad sector remapping.
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.It Ar sectors/unit
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describes the total size of the disk.
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This value must be correct.
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.It Ar "the partition table"
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is the
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.Ux
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partition table, not the
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.Tn DOS
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partition table described in
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.Xr fdisk 8 .
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.El
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.Pp
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The partition table can have up to 8 entries.
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It contains the following information:
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.Bl -tag -width indent
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.It Ar #
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The partition identifier is a single letter in the range
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.Ql a
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to
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.Ql h .
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By convention, partition
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.Ql c
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is reserved to describe the entire disk.
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.It Ar size
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The size of the partition in sectors,
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.Cm K
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(kilobytes - 1024),
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.Cm M
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(megabytes - 1024*1024),
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.Cm G
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(gigabytes - 1024*1024*1024),
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.Cm %
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(percentage of free space
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.Em after
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removing any fixed-size partitions other than partition
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.Ql c ) ,
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or
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.Cm *
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(all remaining free space
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.Em after
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fixed-size and percentage partitions).
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For partition
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.Ql c ,
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a size of
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.Cm *
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indicates the entire disk.
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Lowercase versions of
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.Cm K , M ,
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and
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.Cm G
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are allowed.
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Size and type should be specifed without any spaces between them.
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.Pp
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Example: 2097152, 1G, 1024M and 1048576K are all the same size
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(assuming 512-byte sectors).
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.It Ar offset
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The offset of the start of the partition from the beginning of the
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drive in sectors, or
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.Cm *
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to have
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.Nm
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calculate the correct offset to use (the end of the previous partition plus
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one, ignoring partition
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.Ql c .
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For partition
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.Ql c ,
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.Cm *
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will be interpreted as an offset of 0.
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.It Ar fstype
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Describes the purpose of the partition.
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The example shows all currently used partition types.
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For
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.Tn UFS
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file systems and
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.Xr ccd 4
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partitions, use type
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.Cm 4.2BSD .
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For Vinum drives, use type
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.Cm vinum .
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Other common types are
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.Cm swap
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and
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.Cm unused .
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By convention, partition
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.Ql c
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represents the entire slice and should be of type
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.Cm unused ,
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though
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.Nm
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does not enforce this convention.
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The
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.Nm
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utility
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also knows about a number of other partition types,
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none of which are in current use.
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(See the definitions starting with
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.Dv FS_UNUSED
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in
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.Aq Pa sys/disklabel.h
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for more details.)
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.It Ar fsize
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For
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.Cm 4.2BSD
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and
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.Tn LFS
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file systems only, the fragment size.
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Defaults to 1024 for partitions smaller than 1GB,
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4096 for partitions 1GB or larger.
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.It Ar bsize
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For
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.Cm 4.2BSD
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and
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.Tn LFS
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file systems only, the block size.
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Defaults to 8192 for partitions smaller than 1GB,
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16384 for partitions 1GB or larger.
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.It Ar bps/cpg
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For
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.Cm 4.2BSD
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file systems, the number of cylinders in a cylinder group.
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For
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.Tn LFS
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file systems, the segment shift value.
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Defaults to 16 for partitions smaller than 1GB,
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64 for partitions 1GB or larger.
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.El
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.Pp
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The remainder of the line is a comment and shows the cylinder allocations based
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on the obsolete (but possibly correct) geometry information about the drive.
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The asterisk
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.Pq Ql *
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indicates that the partition does not begin or end exactly on a
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cylinder boundary.
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.Sh EXAMPLES
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.Dl "disklabel da0s1"
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.Pp
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Display the in-core label for the first slice of the
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.Pa da0
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disk, as obtained via
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.Pa /dev/da0s1 .
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(If the disk is
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.Dq dangerously-dedicated ,
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the base disk name should be specified, such as
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.Pa da0 . )
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.Pp
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.Dl "disklabel da0s1 > savedlabel"
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.Pp
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Save the in-core label for
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.Pa da0s1
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into the file
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.Pa savedlabel .
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This file can be used with the
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.Fl R
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option to restore the label at a later date.
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.Pp
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.Dl "disklabel -w -r /dev/da0s1 da2212 foo"
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.Pp
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Create a label for
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.Pa da0s1
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based on information for
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.Dq da2212
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found in
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.Pa /etc/disktab .
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Any existing bootstrap code will be clobbered
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and the disk rendered unbootable.
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.Pp
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.Dl "disklabel -e -r da0s1"
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.Pp
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Read the on-disk label for
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.Pa da0s1 ,
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edit it, and reinstall in-core as well as on-disk.
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Existing bootstrap code is unaffected.
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.Pp
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.Dl "disklabel -e -r -n da0s1"
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.Pp
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Read the on-disk label for
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.Pa da0s1 ,
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edit it, and display what the new label would be (in sectors).
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It does
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.Em not
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install the new label either in-core or on-disk.
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.Pp
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.Dl "disklabel -r -w da0s1 auto"
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.Pp
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Try to auto-detect the required information from
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.Pa da0s1 ,
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and write a new label to the disk.
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Use another
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.Nm Fl e
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command to edit the
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partitioning and file system information.
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.Pp
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.Dl "disklabel -R da0s1 savedlabel"
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.Pp
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Restore the on-disk and in-core label for
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.Pa da0s1
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from information in
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.Pa savedlabel .
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Existing bootstrap code is unaffected.
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.Pp
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.Dl "disklabel -R -n da0s1 label_layout"
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.Pp
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Display what the label would be for
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.Pa da0s1
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using the partition layout in
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.Pa label_layout .
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This is useful for determining how much space would be alloted for various
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partitions with a labelling scheme using
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.Cm % Ns -based
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or
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.Cm *
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partition sizes.
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.Pp
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.Dl "disklabel -B da0s1"
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.Pp
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Install a new bootstrap on
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.Pa da0s1 .
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The boot code comes from
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.Pa /boot/boot .
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On-disk and in-core labels are unchanged.
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.Pp
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.Dl "disklabel -w -B /dev/da0s1 -b newboot da2212"
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.Pp
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Install a new label and bootstrap.
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The label is derived from
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.Xr disktab 5
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information for
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.Dq da2212 ,
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and installed both in-core and on-disk.
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The bootstrap code comes from the file
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.Pa newboot
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in the current working directory.
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.Bd -literal -offset indent
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dd if=/dev/zero of=/dev/da0 bs=512 count=32
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fdisk -BI da0
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dd if=/dev/zero of=/dev/da0s1 bs=512 count=32
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disklabel -w -B da0s1 auto
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disklabel -e da0s1
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.Ed
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.Pp
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Completely wipe any prior information on the disk, creating a new bootable
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disk with a
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.Tn DOS
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partition table containing one slice, covering the whole disk.
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Initialize the label on this slice,
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then edit it.
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The
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.Xr dd 1
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commands are optional, but may be necessary for some
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.Tn BIOS Ns es
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to properly
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recognize the disk.
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.Pp
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This is an example disk label that uses some of the new partition size types
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such as
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.Cm % , M , G ,
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and
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.Cm * ,
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which could be used as a source file for
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.Dq Li "disklabel -R ad0s1c new_label_file" :
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.Bd -literal -offset 4n
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# /dev/ad0s1c:
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type: ESDI
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disk: ad0s1
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label:
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flags:
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bytes/sector: 512
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sectors/track: 63
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tracks/cylinder: 16
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sectors/cylinder: 1008
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cylinders: 40633
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sectors/unit: 40959009
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rpm: 3600
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interleave: 1
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trackskew: 0
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cylinderskew: 0
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headswitch: 0 # milliseconds
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track-to-track seek: 0 # milliseconds
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drivedata: 0
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8 partitions:
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# size offset fstype [fsize bsize bps/cpg]
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a: 400M 0 4.2BSD 4096 16384 75 # (Cyl. 0 - 812*)
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b: 1G * swap
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c: * * unused
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e: 204800 * 4.2BSD
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f: 5g * 4.2BSD
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g: * * 4.2BSD
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.Ed
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.Sh SEE ALSO
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.Xr ccd 4 ,
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.Xr md 4 ,
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.Xr disklabel 5 ,
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.Xr disktab 5 ,
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.Xr boot0cfg 8 ,
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.Xr fdisk 8 ,
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.Xr vinum 8
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.Sh DIAGNOSTICS
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The kernel device drivers will not allow the size of a disk partition
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to be decreased or the offset of a partition to be changed while it is open.
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Some device drivers create a label containing only a single large partition
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if a disk is unlabeled; thus, the label must be written to the
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.Ql a
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partition of the disk while it is open.
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This sometimes requires the desired label to be set in two steps,
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the first one creating at least one other partition,
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and the second one setting the label on the new partition
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while shrinking the
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.Ql a
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partition.
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.Pp
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On some machines, the bootstrap code may not fit entirely in the area
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allocated for it by some file systems.
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As a result,
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it may not be possible to have file systems on some partitions of a
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.Dq bootable
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disk.
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When installing bootstrap code,
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.Nm
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checks for these cases.
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If the installed boot code would overlap a partition of type
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.Dv FS_UNUSED ,
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it is marked as type
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.Dv FS_BOOT .
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The
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.Xr newfs 8
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utility will disallow creation of file systems on
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.Dv FS_BOOT
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partitions.
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Conversely, if a partition has a type other than
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.Dv FS_UNUSED
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or
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.Dv FS_BOOT ,
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.Nm
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will not install bootstrap code that overlaps it.
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.Sh BUGS
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When a disk name is given without a full pathname,
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the constructed device name uses the
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.Ql c
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partition.
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.Pp
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For the i386 architecture, the primary bootstrap sector contains
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an embedded
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.Em fdisk
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table.
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The
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.Nm
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utility takes care to not clobber it when installing a bootstrap only
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.Pq Fl B ,
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or when editing an existing label
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.Pq Fl e ,
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but it unconditionally writes the primary bootstrap program onto
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the disk for
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.Fl w
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or
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.Fl R ,
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thus replacing the
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.Em fdisk
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table by the dummy one in the bootstrap program.
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This is only of
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concern if the disk is fully dedicated, so that the
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.Fx
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disk label
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starts at absolute block 0 on the disk.
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.Pp
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The
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.Nm
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utility
|
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does not perform all possible error checking.
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Warnings are given if partitions overlap,
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if an absolute offset does not match the expected offset,
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if the
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.Ql c
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partition does not start at 0 or does not cover the entire slice,
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if a partition runs past the end of the device,
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and a number of other errors,
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but no warning is given if space remains unused. |