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disklabel(8)
NAME
disklabel - Reads and writes disk pack label
SYNOPSIS
/sbin/disklabel [-r] disk
/sbin/disklabel -p disk [disk_type]
/sbin/disklabel -w [-r] [-t ufs | advfs] disk disktype [packid] [primary-
boot secondary-boot]
/sbin/disklabel -wrn disk disktype [packid]
/sbin/disklabel -e [-r] disk
/sbin/disklabel -R [-r] [-t ufs | advfs] disk protofile [disktype |
primary-boot secondary-boot]
/sbin/disklabel [-N | -W] disk
/sbin/disklabel -z disk
/sbin/disklabel -s partition fstype
/sbin/disklabel [-r] -f image_file
/sbin/disklabel [-w] -f image_file [-t cdfs|ufs|advfs]
[packid] primary_boot secondary_boot
/sbin/disklabel -e -f image_file
FLAGS
-e Edits an existing label.
-f image_file
Specifies the type of image file for operations. The default image
file type is cdfs, to indicate that the image file was created in ISO
9660 Rock Ridge format. The cdfs default applies only when the -f
flag is used.
-n Writes an initial label to a disk which will then be labeled, but
non-bootable.
-N Disallows writing of the pack label area on the specified disk. (See
-W.)
-p Prints label parameters for the specified disk to stdout.
-r Reads or writes the label directly to or from the disk, rather than
operating on the in-memory copy of the label.
-R Restores a disk label that was formatted in a prior operation and
saved in an ASCII file.
-s Sets the file system type (fstype) field in the disk label.
-t ufs|advfs|cdfs
Specifies which type of the local file system the boot blocks
describe, UFS, AdvFS, or CDFS.
-w Writes a standard label on the designated drive.
-W Allows writing of the pack label area on the specified disk. (See
-N.)
-z Zeros (clears) the disk label.
DESCRIPTION
The disklabel command can be used to install, examine, or modify the label
on a disk drive or pack. The disk label contains information about the
disk, such as type, physical parameters, and partitioning.
The disklabel command can be used to change the drive identification or the
disk partitions on the drive, or to replace a damaged label or bootstrap.
The disk label is located on one of the first sectors of each disk (usually
block 0). On machines that require a block-0 bootstrap, the label is
inserted into the bootstrap program.
The disk argument specifies the disk (for example, dsk0 or
/dev/rdisk/dsk0a). If you do not specify the disk partition, disklabel
uses the first partition that has a zero offset. Typically, this is the a
or c partition. Note that if the full path name is used, it must be a
character special device name and not the block device name.
The disktype argument specifies the type of disk. The /etc/disktab file
contains a list of disk types and their parameters and partitions. If you
want disks that are the same type to have different partition parameters,
you must have separate /etc/disktab file entries describing each disk, or
you must edit the disks' labels after installation with the -e flag. If
your disk type is not specified in the /etc/disktab file, disklabel uses
the default partition information in the driver.
There are two copies of a disk label, one located on the disk and one
located in system memory. Because it is faster to access system memory than
to perform I/O, when a system recognizes a disk, it copies the disk label
into memory.
The -r option causes the label to be read from or written to the disk
directly, instead of reading the system's in-memory copy of the label.
When writing, the in-memory copy is also updated if the parameters are
valid. The -r option must be used if there is no label already on the
disk. This option may allow a label to be installed on a disk without
kernel support for a label, such as when labels are first installed on a
system.
The first form of the command is used to examine the label on the specified
disk drive. It displays all of the parameters associated with the drive
and its partition layout. If the disk has no label or if the partition
types on the disk are incorrect, the kernel may have constructed or
modified the label. If you specify the -r flag, the label from the raw
disk is displayed instead of the in-memory label.
The -p option prints the disklabel parameters from /etc/disktab for a
specified disk to stdout. The type of disk is obtained directly by
querying the disk special file. If there is no matching entry in
/etc/disktab for the obtained type, disklabel uses the default partition
information in the driver. If the optional disktype parameter is
specified, it takes precedence over the disk special file, and the
information will be obtained from /etc/disktab if a matching entry is found
for the specified type. If no matching entry is found, the default
partition information from the driver will be used as described above.
The second form of the command, with the -w flag, writes a standard label
on the designated drive. You must specify the disk and the disk type as
described in the /etc/disktab file. The optional packid argument specifies
a pack identification string that contains up to 16 characters. Use quotes
around the packid argument if it contains blanks. If you specify the -r
flag with the -w flag, the disk sectors that contain the label and
bootstrap are written directly; otherwise the existing label is updated in
place without modifying the bootstrap. In either case, the kernel's in-
memory label is replaced. You can specify alternate versions of the
bootstrap files, using the primary-boot and secondary-boot arguments. If
an alternate bootstrap is not specified, the standard bootstrap is used.
If you specify the -f flag with the -w flag, the disk label is written to
the specified image file. The default bootstrap programs are for the CDFS
file system. You can use alternative bootstrap programs by specifying the
-t flag and indicating the file system type in it. Alternatively, you can
specify primary and secondary boot arguments.
The bootstrap programs are located in /mdec. The names of the bootstrap
programs can be specified in the /etc/disktab file, but if they are not
specified, the default names use either the basenameboot syntax for the
primary (block 0) bootstrap or the bootbasename syntax for the secondary
(blocks 1-15 for UFS and blocks 64-95 for AdvFS) bootstrap, where the
basename is the type of disk, such as, rz or re. For example, the names
are /mdec/rzboot and /mdec/bootrz for a UFS rz-type disk. If you specify
the -t advfs option, the default names use either the basenameboot.advfs
syntax for the primary bootstrap or the bootbasename.advfs syntax for the
secondary bootstrap (blocks 64-95), for example, /mdec/rzboot.advfs and
/mdec/bootrz.advfs.
To write an initial label to a non-bootable disk, use the -n option with
the -wr options. When using this form of the command, specify the disk and
disktype. You can also specify the optional packid.
You can edit an existing disk label, using the -e flag. The label is read
from the in-memory kernel copy, or directly from the disk if the -r flag is
specified. The label is formatted and then sent to an editor. If no
editor is specified with the EDITOR environment variable, the vi editor is
used. If vi is not available, the ed editor is used.
Note that if an unexpected error occurs during the ed editing session, the
following message will appear:
Warning, edit session exited abnormally!
You should re-edit the disk label to ensure that you made the
modifications.
When the editor terminates, the formatted label is reread and used to
rewrite the disk label.
If you specify the -R flag, disklabel restores a disk label that was
previously formatted and saved in an ASCII file. The protofile argument
specifies the prototype file that is used to create the label. This file
should be in the same format that is produced when reading or editing a
label. Comments are indicated with number signs (#) and newline. If you
also specify the -r option, a block-0 bootstrap is installed on the
machines that use that type of bootstrap; either the disk type or the names
of the bootstrap files must be specified on such machines.
The -N flag does not allow you to write to the disk pack label area. The
-W flag allows you to write to the disk pack label area. The label sector
is always write-protected when the drive is first opened; the write-enable
flag set by -W persists only until all partitions on the drive are closed.
Note that if you replace an existing label with a new label, the existing
partition information will be copied to the new label if the new label's
partition is marked unused. This may cause disklabel to fail and can be
avoided by first using the -z option to clear the disk label.
You can use the -s option to change the file system type (fstype) in the
disk label. Specify the partition whose type you are changing and the new
fstype. If a partition no longer contains valid file system data, use the
-s option to set the fstype to unused. Or, if the fstype is unused, but the
partition does contain valid data, use the -s option to set a valid fstype.
This prevents inadvertent loss of data, as applications like newfs, mkfdmn,
voldisk, and swapon check the fstype field in the disk label for the
partition usage.
You can set the fstype field to be any of the following:
unused Available for use.
swap Used as swap space.
4.2BSD, ufs, or UFS
Used by a UNIX file system.
AdvFS Used by an AdvFS file system.
cdfs Used by a CDFS file system.
LSMnopriv Used by an LSM nopriv disk.
LSMpriv Used for an LSM private region.
LSMpubl Used for an LSM public region.
LSMsimp Used by an LSM simple disk.
database Used by a database.
raw Used for raw data.
NOTES
· The kernel device drivers do not allow the size of a disk partition to
be decreased or the offset of a partition to be changed while it is
open. Some device drivers create a label containing only a single
large partition if a disk is unlabeled; thus the label must be written
to the a or c partition of the disk while it is open. This sometimes
requires the desired label to be set in two steps, the first one
creating at least one other partition, and the second setting the
label on the new partition while shrinking the a partition.
The kernel does not allow file system information to be set unused for
open partitions. For example, if you want to set the a partition to
unused, you must write the label using a different partition (such as
the c partition). For example:
# disklabel -w /dev/rdisk/dsk0c rz56
If a file system exists for an open partition, the existing file
system information is copied to the new label. This preserves the
existing information without returning an error.
· When using LSM, if you try to recover a replaced mirror disk and the
disk has been replaced with a new disk, disklabel fails with the
following error, when attempting to write the new label:
disklabel: ioctl DIOCSDINFO: open partition would move or shrink
Remove the disk from LSM before attempting to write the new disklabel:
# voldisk rm rz8
# disklabel -wr rz8 rz28
EXAMPLES
The following example clears the existing label, writes a new label, and
then displays the current label:
# disklabel -z rz6
# disklabel -rw rz6 rzw7s
# disklabel -r rz6
# /dev/rdisk/dsk6a:
type: SCSI
disk: rzw7s
label:
flags:
bytes/sector: 512
sectors/track: 71
tracks/cylinder: 15
sectors/cylinder: 1065
cylinders: 1900
sectors/unit: 2023500
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 cpg]
a: 131072 0 unused 1024 8192 # (Cyl. 0 - 123*)
b: 262144 131072 unused 1024 8192 # (Cyl. 123*- 369*)
c: 2023500 0 unused 1024 8192 # (Cyl. 0 - 1899)
d: 163840 1703936 unused 1024 8192 # (Cyl. 1599*- 1753*)
e: 32768 1867776 unused 1024 8192 # (Cyl. 1753*- 1784*)
f: 122956 1900544 unused 1024 8192 # (Cyl. 1784*- 1899*)
g: 1310720 393216 unused 1024 8192 # (Cyl. 369*- 1599*)
h: 319564 1703936 unused 1024 8192 # (Cyl. 1599*- 1899*)
Note that the asterisks in the cpg column indicate that the beginning or
ending cylinders do not fall exactly on a block boundary.
The following example marks partition dsk4c for use by a database:
# disklabel -s dsk4c database
The following example marks partition dsk4c as unused, which means it is
available for use.
# disklabel -s dsk4c unused
The following example shows how a disk label is written to a a CDFS image
file and then read from it:
# disklabel -w -f system.image
# disklabel -f system.image
# system.image:
type: unknown
disk: CDROM
label:
flags: removeable
bytes/sector: 512
sectors/track: 1728
tracks/cylinder: 1
sectors/cylinder: 1
cylinders: 1
sectors/unit: 1728
rpm: 300
interleave: 1
trackskew: 0
cylinderskew: 0
headswitch: 0 # milliseconds
track-to-track seek: 0 # milliseconds
drivedata: 0
3 partitions:
# size offset fstype [fsize bsize cpg]
a: 1728 0 CDFS # (Cyl. 0 -
1727)
b: 0 0 unused 0 0 # (Cyl. 0 -
-1)
c: 1728 0 unused 0 0 # (Cyl. 0 -
1727)
#
FILES
/dev/disk Contains device special files, such as disk0a.
/dev/rdisk Contains raw device special files, such as disk1c.
/etc/disktab Contains information about disks and drives.
/mdec/xxboot Primary bootstrap programs.
/mdec/bootxx Secondary bootstrap programs.
RELATED INFORMATION
Files: disklabel(4), disktab(4), rz(7), ra(7)
Functions: check_usage(3), set_usage(3)
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Alphabetical
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