and write disk pack label
utility can be used to install,
examine, or modify the label on a disk drive or pack. The disk label contains
information about disk characteristics (size, type, etc.) and the partition
layout, stored on the disk itself. It is used by the operating system to
optimize disk I/O and locate the filesystems resident on the disk.
supports 15 configurable partitions,
‘a’ through ‘p’, excluding ‘c’. The
‘c’ partition describes the entire physical disk, is
automatically created by the kernel, and cannot be modified or deleted by
. By convention, the ‘a’
partition of the boot disk is the root partition, and the ‘b’
partition of the boot disk is the swap partition, but all other letters can be
used in any order for any other partitions as desired.
The options are as follows:
- Automatically allocate all the disk space in the
OpenBSD portion of the disk in the recommended
- Clear the system's in-core copy of the label and update it
based on the on-disk label.
- Use the default label. This
ignores any existing OpenBSD disk label on the
- Use the built-in command-driven label editor described
- Edit an existing disk label using the editor specified in
EDITOR environment variable, or
vi(1) if none is
- Write entries to file in
for any partitions for which mount point information is known. The entries
will be written using disklabel UIDs. The -F
flag is only valid when used in conjunction with the
-E or -R flags.
If file already exists, it will be
- The same as -F except that
entries will be written using disk device names.
- Print partition sizes in human readable format.
- Make no permanent changes to the disklabel (useful for
- Print partition sizes in
unit instead of sectors. Valid units are
b(ytes), c(ylinders), k(ilobytes), m(egabytes), g(igabytes) and
- Restore a disk label that was formatted in a prior
operation and saved in an ASCII file.
- Read the template for automatic allocation from
file instead of using the builtin one.
DISK ALLOCATION below for the format.
- Format the label as a
- Print additional information during operation (verbose
- Write a standard label on the designated drive.
- Specify the disk to
operate on. It can be specified by its full pathname, by an abbreviated
disk form, or by its disklabel UID. In its abbreviated form, the path to
the device, the ‘r’ denoting “raw device”, and
the partition letter, can all be omitted. For example, the first IDE disk
can be specified as either /dev/rwd0c,
- Specify a disktype entry
- Specify a pack identification string for the device (see
- Used with the restore option
(-R) to specify a file to read an ASCII label
The first form of the command (read) is used to examine the label on the named
disk drive. It will display all of the parameters associated with the drive
and its partition layout. The kernel's in-core copy of the label is displayed;
if the disk has no label, or the partition types on the disk are incorrect,
the kernel may have constructed or modified the label.
The second form of the command (write) is used to write a standard label on the
designated drive. The drive parameters and partitions are taken from that
file. If different disks of the same physical type are to have different
partitions, it will be necessary to have separate disktab entries describing
each, or to edit the label after installation as described below. The optional
argument is a pack identification string, up to 16 characters long. The pack
ID must be quoted if it contains blanks. The existing label will be updated
via the in-core copy and any bootstrap code will be unaffected.
In the third form of the command (edit), the label is read from the in-core
kernel copy and then supplied to an editor for changes. If no editor is
specified in an
When the editor terminates, the formatted label is reread and used to rewrite
the disk label. Existing bootstrap code is unchanged.
The built-in label editor (fourth form) provides a simple interactive label
editor. Some commands or prompts take an optional unit. Available units are
‘b’ for bytes, ‘c’ for cylinders,
‘k’ for kilobytes, ‘m’ for megabytes,
‘g’ for gigabytes, and ‘t’ for terabytes. If no
unit is given, the default is to use sectors (usually 512 bytes).
Quantities are rounded to the nearest cylinder when units are specified for
sizes (or offsets). At prompts that request a size,
’ may be entered to indicate the rest
of the available space, ‘%’ for percentage of total, and
‘&’ for percentage free. Commands may be aborted by entering
’ (Control-D). Entering
’ at the main
’ prompt will exit the editor.
The editor commands are as follows:
- Display help message with all available commands. There is
also (simple) context-sensitive help available at most prompts.
- Allocate all the disk space in the recommended manner. See
- Add new partition. This option adds a new partition to the
disk label. If no partition letter is specified (a-p), the user will be
prompted for one.
- Set OpenBSD disk boundaries. This
option tells disklabel which parts of the
disk it is allowed to modify. This option is probably only useful for
partition tables where the ending sector in the MBR is incorrect. The user
may enter ‘
*’ at the
“Size” prompt to indicate the entire size of the disk (minus
the starting sector). This is useful for disks where the fdisk partition
table is incapable of storing the real size. Note: data may become
corrupted if boundaries are extended such that they overlap with other
resident operating systems.
- Change the size of an existing partition. If no partition
is specified, the user will be prompted for one. The new size may be in
terms of the aforementioned units and may also be prefixed with
-’ to change the size by a relative
- Sets the disk label to the default values as reported by
the kernel. This simulates the case where there is no disk label.
- Delete an existing partition (or
*’ to delete all partitions). If no
partition is specified, the user will be prompted for one.
- Edit drive parameters. This option is used to set the
following parameters: disk type, a descriptive label string,
sectors/track, tracks/cylinder, sectors/cylinder, number of cylinders,
total sectors, rpm, and interleave.
- Set disk geometry based on what the
disk or user
thinks (the user geometry is simply what the
label said before disklabel made any
- Change the disklabel UID, specified as a 16-character
hexadecimal string. If set to all zeros, a new UID will automatically be
allocated when the disklabel is written to disk.
- Print the disk label header.
- Display this manual page. The manual page is piped through
the pager specified by the
environment variable or 'less' if
is not set.
- Modify parameters for an existing partition. If no
partition is specified, the user will be prompted for one. This option
allows the user to change the filesystem type, starting offset, partition
size, and mount point for the specified partition. If expert mode is
enabled (see X below), then block fragment
size, block size, and cylinders per group can also be modified. Note that
not all parameters are configurable for non-BSD
- Name the mount point for an existing partition. If no
partition is specified, the user will be prompted for one. This option is
only valid if disklabel was invoked with the
- Print the current partition list. If a
unit is given, the size and offsets are
displayed in terms of the specified unit. If the unit is ‘*’
it is automatically determined by the size of the smallest partition.
- Quit the editor. If any changes have been made, the user
will be asked whether or not to save the changes to the on-disk
- Resize a partition in an automatically allocated label,
compacting unused space between partitions with a higher offset. The last
partition will be shrunk if necessary. Works only for automatically
allocated labels with no spoofed partitions.
- Recalculate free space. This command displays all the free
areas on the disk and the total number of free sectors.
- Save the label to a file in ASCII format (suitable for
loading via the -R option). If no path is
specified, the user will be prompted for one.
- Undo all changes made since entering the editor.
- Undo (or redo) last change. Entering
u once will undo the last change. Entering it
again will restore the change.
- Write the label to disk. This option will commit any
changes to the on-disk label.
- Toggle “expert mode”. By default, some
settings are reserved for experts only (such as the block and fragment
size on ffs partitions).
- Exit the editor without saving any changes to the on-disk
- Zero out the existing partition table and mountpoint
information, leaving only the 'c' partition. The drive parameters are not
In the restore form of the command (fifth form), 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. Any existing bootstrap code will be unaffected.
The final three forms of disklabel
are used to
install bootstrap code on machines where the bootstrap is part of the label.
Note that when a disk has no real BSD
kernel creates a default label so that the disk can be used. This default
label will include other partitions found on the disk if they are supported on
your architecture. For example, on systems that support
the default label will also include DOS and Linux partitions. However, these
entries are not dynamic, they are fixed at the time
is run. That means that subsequent
changes that affect non-OpenBSD
partitions will not be
present in the default label, though they may be updated by hand. To see the
default label, run disklabel
can then be run with the -e
flag and any entries
pasted as desired from the default label into the real one.
option and the editor command
automatically create a disklabel with a set of
partitions suitable for a majority of OpenBSD
installations. Any existing OpenBSD
disklabel on the
disk is ignored, but native partitions that would normally be spoofed are
preserved in the disklabel, and are not modified during the allocation
Disk size determines the set of partitions which are created. Each partition is
allocated space between a specified minimum and maximum. Initially, each
partition is allocated its minimum space; remaining space is split between the
partitions according to the given percentages, up to their maximum allowed
space. Space left after all partitions have reached their maximum size is left
unallocated. The sizes below are approximations, and may vary from
architecture to architecture.
Disks > 7 Gigabytes
Disks > 2 Gigabytes
/ 5% of disk. 80M – 1G
swap 5% of disk. 80M – 2x max physical memory
/tmp 8% of disk. 120M – 4G
/var 13% of disk. 80M – 2x size of crash dump
/usr 5% of disk. 900M – 2G
/usr/X11R6 3% of disk. 512M – 1G
/usr/local 10% of disk. 2G – 10G
/usr/src 2% of disk. 1G – 2G
/usr/obj 4% of disk. 1.3G – 2G
/home 45% of disk. 1G – 300G
Disks > 700 Megabytes
/ 5% of disk. 800M – 2G
swap 10% of disk. 80M – 2x max physical memory
/usr 78% of disk. 900M – 3G
/home 7% of disk. 256M – 2G
/ 95% of disk. 700M – 4G
swap 5% of disk. 1M – 2x max physical memory
A template for the automatic allocation can be passed to disklabel using the
option. The template consists of one line per
partition, with each line giving mountpoint, min-max size range, and
percentage of disk, space-separated. Max can be unlimited by specifying '*'.
If only mountpoint and min size are given, the partition is created with that
swap 80M-256M 10%
/tmp 120M-4G 8%
/var 80M-4G 13%
/usr 900M-2G 5%
/usr/X11R6 512M-1G 3%
/usr/local 2G-10G 10%
/usr/src 1G-2G 2%
/usr/obj 1.3G-2G 4%
/home 1G-* 45%
- Disk description file.
- Primary bootstrap.
- Secondary bootstrap.
Display the in-core label for sd0 as obtained via
# disklabel sd0
Create a label for sd0 based on information for “sd2212” found in
. Any existing bootstrap code will be
# disklabel -w /dev/rsd0c sd2212
Read the on-disk label from a disk with DUID 3eb7f9da875cb9ee, edit it and
reinstall in-core as well as on-disk. Existing bootstrap code is unaffected.
# disklabel -E 3eb7f9da875cb9ee
Restore the on-disk and in-core label for sd0 from information in
. Existing bootstrap code is unaffected.
# disklabel -R sd0 mylabel
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. 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’
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.
On some machines the bootstrap code may not fit entirely in the area allocated
for it by some filesystems. As a result, it may not be possible to have
filesystems on some partitions of a “bootable” disk. When
installing bootstrap code, disklabel
these cases. If the installed boot code would overlap a partition of type
it is marked as type
disallow creation of filesystems on
partitions. Conversely, if a partition has a type other than
will not install bootstrap code that
The maximum disk and partition size is 64PB.
On some machines, such as Sparc64, partition tables may not exhibit the full
functionality described above.