bsdlabel
—
read and write BSD label
bsdlabel |
[ -A ]
disk |
-f
file |
bsdlabel |
-w
[-An ]
[]
[-m
machine ]
disk |
-f
file
[type ] |
bsdlabel |
-e
[-An ]
[]
[-m
machine ]
disk |
-f
file |
bsdlabel |
-R
[-An ]
[]
[-m
machine ]
[-f ]
disk |
-f
file
protofile |
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.
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.
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.
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.
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.
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.
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.
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.
- /boot/boot
- Default boot image.
- /etc/disktab
- Disk description file.
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).
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
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.
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.
ccd(4),
geom(4),
md(4),
disktab(5),
boot0cfg(8),
gpart(8),
newfs(8)
The
disklabel
utility appeared in
4.3BSD-Tahoe.