BSDLABEL(8) FreeBSD System Manager's Manual BSDLABEL(8)
NAME
bsdlabel - read and write BSD label
SYNOPSIS
bsdlabel [-A] disk | -f file
bsdlabel -w [-An] [-B [-b boot]] [-m machine] disk | -f file [type]
bsdlabel -e [-An] [-B [-b boot]] [-m machine] disk | -f file
bsdlabel -R [-An] [-B [-b boot]] [-m machine] [-f] disk | -f file
protofile
DESCRIPTION
The bsdlabel utility installs, examines or modifies the BSD label on a
disk partition, or on a file containing a partition image. In addition,
bsdlabel can install bootstrap code.
Disk Device Name
When specifying the device (i.e., when the -f option is not used), the
/dev/ path prefix may be omitted; the bsdlabel utility will automatically
prepend it.
General Options
The -A option enables processing of the historical parts of the BSD
label. If the option is not given, suitable values are set for these
fields.
The -f option tells bsdlabel that the program will operate on a file
instead of a disk partition.
The -n option stops the bsdlabel program right before the disk would have
been modified, and displays the result instead of writing it.
The -m machine argument forces bsdlabel to use a layout suitable for a
different architecture. Current valid values are i386 and amd64. If
this option is omitted, bsdlabel will use a layout suitable for the
current machine.
Reading the Disk Label
To examine the label on a disk drive, use the form
bsdlabel [-A] [-m machine] disk
disk represents the disk in question, and may be in the form da0 or
/dev/da0. It will display the partition layout.
Writing a Standard Label
To write a standard label, use the form
bsdlabel -w [-An] [-m machine] disk [type]
If the drive type is specified, the entry of that name in the disktab(5)
file is used; otherwise, or if the type is specified as 'auto', a default
layout is used.
Editing an Existing Disk Label
To edit an existing disk label, use the form
bsdlabel -e [-An] [-m machine] disk
This command opens the disk label in the default editor, and when the
editor exits, the label is validated and if OK written to disk.
Restoring a Disk Label From a File
To restore a disk label from a file, use the form
bsdlabel -R [-An] [-m machine] disk protofile
The bsdlabel utility is capable of restoring a disk label that was
previously saved in a file in ASCII format. The prototype file used to
create the label should be in the same format as that produced when
reading or editing a label. Comments are delimited by `#' and newline.
Installing Bootstraps
If the -B option is specified, bootstrap code will be read from the file
/boot/boot and written to the disk. The -b boot option allows a
different file to be used.
FILES
/boot/boot Default boot image.
/etc/disktab Disk description file.
SAVED FILE FORMAT
The bsdlabel utility uses an ASCII version of the label when examining,
editing, or restoring a disk label. The format is:
8 partitions:
# size offset fstype [fsize bsize bps/cpg]
a: 81920 16 4.2BSD 2048 16384 5128
b: 1091994 81936 swap
c: 1173930 0 unused 0 0 # "raw" part, don't edit
If the -A option is specified, the format is:
# /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 16 4.2BSD 1024 8192 16
b: 160000 81936 swap
c: 1173930 0 unused 0 0 # "raw" part, don't edit
Lines starting with a `#' mark are comments.
The partition table can have up to 8 entries. It contains the following
information:
# The partition identifier is a single letter in the range `a' to
`h'. By convention, partition `c' is reserved to describe the
entire disk.
size The size of the partition in sectors, K (kilobytes - 1024), M
(megabytes - 1024*1024), G (gigabytes - 1024*1024*1024), %
(percentage of free space after removing any fixed-size
partitions other than partition `c'), or * (all remaining free
space after fixed-size and percentage partitions). For partition
`c', a size of * indicates the entire disk. Lowercase versions
of suffixes K, M, and G are allowed. Size and suffix should be
specified without any spaces between them.
Example: 2097152, 1G, 1024M and 1048576K are all the same size
(assuming 512-byte sectors).
offset The offset of the start of the partition from the beginning of
the drive in sectors, or * to have bsdlabel calculate the correct
offset to use (the end of the previous partition plus one,
ignoring partition `c'). For partition `c', * will be
interpreted as an offset of 0. The first partition should start
at offset 16, because the first 16 sectors are reserved for
metadata.
fstype Describes the purpose of the partition. The above example shows
all currently used partition types. For UFS file systems and
ccd(4) partitions, use type 4.2BSD. For Vinum drives, use type
vinum. Other common types are swap and unused. By convention,
partition `c' represents the entire slice and should be of type
unused, though bsdlabel does not enforce this convention. The
bsdlabel utility also knows about a number of other partition
types, none of which are in current use. (See the definitions
starting with FS_UNUSED in <sys/disklabel.h> for more details.)
fsize For 4.2BSD file systems only, the fragment size; see newfs(8).
bsize For 4.2BSD file systems only, the block size; see newfs(8).
bps/cpg
For 4.2BSD file systems, the number of cylinders in a cylinder
group; see newfs(8).
EXAMPLES
Display the label for the first slice of the da0 disk, as obtained via
/dev/da0s1:
bsdlabel da0s1
Save the in-core label for da0s1 into the file savedlabel. This file can
be used with the -R option to restore the label at a later date:
bsdlabel da0s1 > savedlabel
Create a label for da0s1:
bsdlabel -w /dev/da0s1
Read the label for da0s1, edit it, and install the result:
bsdlabel -e da0s1
Read the on-disk label for da0s1, edit it, and display what the new label
would be (in sectors). It does not install the new label either in-core
or on-disk:
bsdlabel -e -n da0s1
Write a default label on da0s1. Use another bsdlabel -e command to edit
the partitioning and file system information:
bsdlabel -w da0s1
Restore the on-disk and in-core label for da0s1 from information in
savedlabel:
bsdlabel -R da0s1 savedlabel
Display what the label would be for da0s1 using the partition layout in
label_layout. This is useful for determining how much space would be
allotted for various partitions with a labeling scheme using %-based or *
partition sizes:
bsdlabel -R -n da0s1 label_layout
Install a new bootstrap on da0s1. The boot code comes from /boot/boot:
bsdlabel -B da0s1
Install a new label and bootstrap. The bootstrap code comes from the
file newboot in the current working directory:
bsdlabel -w -B -b newboot /dev/da0s1
Completely wipe any prior information on the disk, creating a new
bootable disk with a DOS partition table containing one slice, covering
the whole disk. Initialize the label on this slice, then edit it. The
dd(1) commands are optional, but may be necessary for some BIOSes to
properly recognize the disk:
dd if=/dev/zero of=/dev/da0 bs=512 count=32
gpart create -s MBR da0
gpart add -t freebsd da0
gpart set -a active -i 1 da0
gpart bootcode -b /boot/mbr da0
dd if=/dev/zero of=/dev/da0s1 bs=512 count=32
bsdlabel -w -B da0s1
bsdlabel -e da0s1
This is an example disk label that uses some of the new partition size
types such as %, M, G, and *, which could be used as a source file for
"bsdlabel -R ada0s1 new_label_file":
# /dev/ada0s1:
8 partitions:
# size offset fstype [fsize bsize bps/cpg]
a: 400M 16 4.2BSD 4096 16384 75 # (Cyl. 0 - 812*)
b: 1G * swap
c: * * unused
e: 204800 * 4.2BSD
f: 5g * 4.2BSD
g: * * 4.2BSD
DIAGNOSTICS
The kernel device drivers will not allow the size of a disk partition to
be decreased or the offset of a partition to be changed while it is open.
COMPATIBILITY
Due to the use of an uint32_t to store the number of sectors, BSD labels
are restricted to a maximum of 2^32-1 sectors. This usually means 2TB of
disk space. Larger disks should be partitioned using another method such
as gpart(8).
The various BSDs all use slightly different versions of BSD labels and
are not generally compatible.
SEE ALSO
ccd(4), geom(4), md(4), disktab(5), boot0cfg(8), gpart(8), newfs(8)
HISTORY
The disklabel utility appeared in 4.3BSD-Tahoe.
FreeBSD 13.1-RELEASE-p6 October 5, 2016 FreeBSD 13.1-RELEASE-p6
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