sbin/disklabel/disklabel.8

.\"	$OpenBSD: disklabel.8,v 1.157 2024/03/22 21:49:52 jan Exp $
.\"	$NetBSD: disklabel.8,v 1.9 1995/03/18 14:54:38 cgd Exp $
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.\"	@(#)disklabel.8	8.2 (Berkeley) 4/19/94
.\"
.Dd $Mdocdate: March 22 2024 $
.Dt DISKLABEL 8
.Os
.Sh NAME
.Nm disklabel
.Nd read and write disk pack label
.Sh SYNOPSIS
.Nm disklabel
.Op Fl Acdtv
.Op Fl h | p Ar unit
.Op Fl T Ar file
.Ar disk
.Nm disklabel
.Fl w
.Op Fl Acdnv
.Op Fl T Ar file
.Ar disk disktype
.Op Ar packid
.Nm disklabel
.Fl e
.Op Fl Acdnv
.Op Fl T Ar file
.Ar disk
.Nm disklabel
.Fl E
.Op Fl Acdnv
.Op Fl F Ns | Ns Fl f Ar file
.Op Fl T Ar file
.Ar disk
.Nm disklabel
.Fl R
.Op Fl nv
.Op Fl F Ns | Ns Fl f Ar file
.Ar disk protofile
.Sh DESCRIPTION
The
.Nm
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
.Pq 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.
.Pp
.Nm
supports 15 configurable partitions,
.Sq a
through
.Sq p ,
excluding
.Sq c .
The
.Sq c
partition describes the entire physical disk, is automatically created
by the kernel, and cannot be modified or deleted by
.Nm .
By convention, the
.Sq a
partition of the boot disk is the root partition, and the
.Sq 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.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl A
Automatically allocate all the disk space in the
.Ox
portion of the disk in the recommended manner.
See
.Sx AUTOMATIC DISK ALLOCATION ,
below.
.It Fl c
Clear the system's in-core copy of the label and update it based on
the on-disk label.
.It Fl d
Use the
.Em default
label.
This ignores any existing
.Ox
disk label on the disk.
.It Fl E
Use the built-in command-driven label editor described below.
.It Fl e
Edit an existing disk label using the editor specified in the
.Ev EDITOR
environment variable, or
.Xr vi 1
if none is specified.
.It Fl F Ar file
Write entries to
.Ar file
in
.Xr fstab 5
format for any partitions for which mount point information is known.
The entries will be written using disklabel UIDs.
The
.Fl F
flag is only valid when used in conjunction with the
.Fl E
or
.Fl R
flags.
If
.Ar file
already exists, it will be overwritten.
.It Fl f Ar file
The same as
.Fl F
except that entries will be written using disk device names.
.It Fl h
Print partition sizes in human readable format.
.It Fl n
Make no permanent changes to the disklabel
.Pq useful for debugging purposes .
.It Fl p Ar unit
Print partition sizes in
.Ar unit
instead of sectors.
Valid units are b(ytes), c(ylinders), k(ilobytes), m(egabytes), g(igabytes)
and t(erabytes).
.It Fl R
Restore a disk label that was formatted in a prior operation and
saved in an ASCII file.
.It Fl T Ar file
Read the template for automatic allocation from
.Ar file
instead of using the builtin one.
See
.Sx AUTOMATIC DISK ALLOCATION
below for the format.
If
.Ar file
is a single dash
.Pq Sq - ,
the template is read from the standard input.
.It Fl t
Format the label as a
.Xr disktab 5
entry.
.It Fl v
Print additional information during operation
.Pq verbose mode .
.It Fl w
Write a standard label on the designated drive.
.It Ar disk
Specify the
.Ar 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
.Sq r
denoting
.Qq raw device ,
and the partition letter, can all be omitted.
For example, the first IDE disk can be specified as either
.Pa /dev/rwd0c ,
.Pa /dev/wd0c ,
or
.Ar wd0 .
.It Ar disktype
Specify a
.Ar disktype
entry from the
.Xr disktab 5
database.
.It Ar packid
Specify a pack identification string for the device
.Pq see below .
.It Ar protofile
Used with the restore option
.Pq Fl R
to specify a file to read an ASCII label from.
.El
.Pp
The first form of the command
.Pq 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.
.Pp
The second form of the command
.Pq 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.
.Pp
In the third form of the command
.Pq 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
.Ev EDITOR
environment variable,
.Xr vi 1
is used.
When the editor terminates, the formatted label is reread and
used to rewrite the disk label.
.Pp
The built-in label editor
.Pq fourth form
provides a simple interactive label editor.
The editor prompt contains information about the state of the edit
process.
.Pp
.Dl Ar disk Ns *>
.Pp
Where
.Ar disk
is the name of the disk being edited,
.Sq *
means that the in-memory copy of the partition table has been modified but
not yet written to disk.
.Pp
Some commands or prompts take an optional unit.
Available units are
.Sq b
for bytes,
.Sq c
for cylinders,
.Sq k
for kilobytes,
.Sq m
for megabytes,
.Sq g
for gigabytes,
and
.Sq t
for terabytes.
If no unit is given, the default is to use sectors
(usually 512 bytes).
.Pp
Quantities are rounded to the nearest
cylinder when units are specified for sizes
.Pq or offsets .
At prompts that request a size,
.Ql *
may be entered to indicate the rest of the available space,
.Sq %
for percentage of total, and
.Sq &
for percentage free.
Commands may be aborted by entering
.Ql ^D
.Pq Control-D .
Entering
.Ql ^D
at the main prompt will exit the editor.
.Pp
The editor commands are as follows:
.Bl -tag -width "p [unit] "
.It Cm \&? | h
Display help message with all available commands.
There is also
.Pq simple
context-sensitive help available at most prompts.
.It Cm A
Allocate all the disk space in the recommended manner.
See
.Sx AUTOMATIC DISK ALLOCATION ,
below.
.It Cm a Op Ar part
Add new partition.
This option adds a new partition to the disk label.
If no partition letter is specified
.Pq a\-p ,
the user will be prompted for one.
.It Cm b
Set
.Ox
disk boundaries.
This option tells
.Nm
which parts of the disk it is allowed to modify.
This option is probably only useful for ports with
.Xr fdisk 8
partition tables where the ending sector in the MBR is incorrect.
The user may enter
.Ql *
at the
.Dq Size
prompt to indicate the entire size of the disk
.Pq 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.
.It Cm c Op Ar part
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
.Ql +
or
.Ql -
to change the size by a relative amount.
.It Cm D
Sets the disk label to the default values as reported by the kernel.
This simulates the case where there is no disk label.
.It Cm d Op Ar part
Delete an existing partition (or
.Ql *
to delete all partitions).
If no partition is specified, the user will be prompted for one.
.It Cm e
Edit label description, e.g. 'UMIS RPJTJ256MED'.
.It Cm i
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.
.It Cm l Op Ar unit
Print the disk label header.
.It Cm M
Display this manual page.
The manual page is piped through the pager specified by the
.Ev PAGER
environment variable or 'less' if
.Ev PAGER
is not set.
.It Cm m Op Ar part
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.
.It Cm n Op Ar part
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
.Nm
was invoked with the
.Fl f
flag.
.It Cm p Op Ar unit
Print the current partition list.
If a
.Em unit
is given, the size and offsets are displayed in terms of the
specified unit.
If the unit is
.Sq * ,
it is automatically determined by the size of the smallest
partition.
.It Cm q
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 label.
.It Cm R Op Ar part
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.
.It Cm r
Recalculate free space.
This command displays all the free areas on the disk and the total
number of free sectors.
.It Cm s Op Ar path
Save the label to a file in ASCII format (suitable for loading via the
.Fl R
option).
If no path is specified, the user will be prompted for one.
.It Cm U
Undo all changes made since entering the editor.
.It Cm u
Undo
.Pq or redo
last change.
Entering
.Em u
once will undo the last change.
Entering it again will restore the change.
.It Cm w
Write the label to disk.
This option will commit any changes to the on-disk label.
.It Cm x
Exit the editor without saving any changes to the on-disk label.
.It Cm z
Zero out the existing partition table and mount point information,
leaving only the 'c' partition.
The drive parameters are not changed.
.El
.Pp
In the restore form of the command
.Pq 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
.Ar #
and newline.
.Pp
Note that when a disk has no real
.Bx
disklabel, the 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
.Xr fdisk 8
partitions the default label will also include DOS and Linux partitions.
However, these entries are not dynamic, they are fixed at the time
.Nm
is run.
That means that subsequent changes that affect
.Pf non- Ox
partitions will not be present in the default label,
though they may be updated by hand.
To see the default label, run
.Nm
with the
.Fl d
flag.
.Nm
can then be run with the
.Fl e
flag and any entries pasted as desired from the default label into the real one.
.Sh AUTOMATIC DISK ALLOCATION
The
.Fl A
option and the editor command
.Cm A
create disklabels that distribute a disk's free space into a set of
partitions appropriate for an
.Ox
installation.
The exact set of partitions created depends on available free space,
how fragmented the free space is
and some machine dependent variables, but will be approximately:
.Bl -column "/usr/X11R6" \
"999MB \(en 999MB" "999MB \(en 999MB" "999MB \(en 999MB" \
"< 700MB"
.It \
Ta Sy > 10GB Free Ta Sy > 2.5GB Ta Sy > 700MB Ta \
Sy < 700MB
.It Sy / \
Ta 150MB \(en \0\01GB Ta 800MB \(en \0\02GB Ta 700MB \(en \0\04GB Ta \
1MB \(en 2GB
.It Sy swap \
Ta \080MB \(en 256MB Ta \080MB \(en 256MB Ta \0\01MB \(en 256MB Ta
.It Sy /usr \
Ta 1.5GB \(en \030GB Ta 1.5GB \(en \030GB Ta Ta
.It Sy /home \
Ta \0\01GB \(en 300GB Ta 256MB \(en \0\02GB Ta Ta
.It Sy /tmp \
Ta 120MB \(en \0\04GB Ta Ta Ta
.It Sy /var \
Ta \080MB \(en \0\04GB Ta Ta Ta
.It Sy /usr/X11R6 \
Ta 384MB \(en \0\01GB Ta Ta Ta
.It Sy /usr/local \
Ta \0\01GB \(en \020GB Ta Ta Ta
.It Sy /usr/src \
Ta \0\02GB \(en \0\05GB Ta Ta Ta
.It Sy /usr/obj \
Ta \0\05GB \(en \0\06GB Ta Ta Ta
.El
.Pp
The
.Fl A
option displays the partition set that would be created and
.Fl wA
writes it to disk.
.Pp
The default set can be overridden with
.Fl T .
Each line of input uses three fields to describe a partition.
There must not be whitespace before the first field,
fields are separated by whitespace and fields cannot contain whitespace.
.Pp
The first field is the partition's mount point or one of the
special tokens
.Sq RAID
or
.Sq SWAP .
.Pp
The second field is the partition size.
This can be
.Sq *
to make the partition as large as possible,
an exact size (e.g. 1G) or a size range
(e.g. 1M-10G or 1G-*).
.Pp
The third field is the partition's share of any space left after all
minimum sizes are accounted for.
This is expressed as a percentage from 0 (the default) to 100
(e.g. 37%).
The last partition receives all remaining free space up to its
maximum size no matter what percentage is specified.
.Sh FILES
.Bl -tag -width "/etc/disktabXXX"
.It Pa /etc/disktab
Disk description file.
.El
.Sh EXAMPLES
Display, respectively, the current label, the default label and the
default auto allocation for sd0:
.Bd -literal -offset indent
# disklabel sd0
# disklabel -d sd0
# disklabel -A sd0
.Ed
.Pp
Write the default auto allocation to sd0:
.Pp
.Dl # disklabel -wA sd0
.Pp
Edit the label for the disk with DUID 3eb7f9da875cb9ee:
.Pp
.Dl # disklabel -E 3eb7f9da875cb9ee
.Pp
Restore the label for sd0 from information in
.Pa mylabel :
.Pp
.Dl # disklabel -R sd0 mylabel
.Pp
Put largest contiguous area of free space on sd0 into a single RAID partition:
.Dl # echo 'RAID *' | disklabel -wAT- sd0
.Pp
Write the auto allocation defined in
.Pa /template
to sd0:
.Pp
.Dl # disklabel -wAT/template sd0
.Pp
A template file that results in an auto allocation similar to the
default one for a disk with 5GB of free space is:
.Bl -column /home 1300MM256M 75% -offset indent
.It / Ta \0800M\(en2G Ta \05%
.It swap Ta \0\080M\(en256M Ta 10%
.It /usr Ta 1300M\(en\)3G Ta 75%
.It /home Ta \0256M\(en2G Ta 10%
.El
.Sh 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.
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
.Sq 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
.Sq a
partition.
.Sh SEE ALSO
.Xr softraid 4 ,
.Xr disklabel 5 ,
.Xr disktab 5 ,
.Xr installboot 8 ,
.Xr scan_ffs 8
.Sh HISTORY
The
.Nm
utility appeared in
.Bx 4.3 Tahoe .
.Sh CAVEATS
The maximum disk and partition size is 64PB.
.Pp
On some machines, such as Sparc64, partition tables
may not exhibit the full functionality described above.