path: root/sbin/disklabel/disklabel.8

.\"	$OpenBSD: disklabel.8,v 1.43 2001/12/13 20:16:48 mpech Exp $
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.\"	@(#)disklabel.8	8.2 (Berkeley) 4/19/94
.\"
.Dd October 27, 1997
.Dt DISKLABEL 8
.Os
.Sh NAME
.Nm disklabel
.Nd read and write disk pack label
.Sh SYNOPSIS
.Nm disklabel
.Op Fl n
.Op Fl cd Li \&| Fl r
.Op Fl t
.Op Fl v
.Ar disk
.Nm disklabel
.Fl w
.Op Fl n
.Op Fl cd Li \&| Fl r
.Op Fl v
.Ar disk Ar disktype
.Oo Ar packid Oc
.Nm disklabel
.Fl e
.Op Fl n
.Op Fl cd Li \&| Fl r
.Op Fl v
.Ar disk
.Nm disklabel
.Fl E
.Op Fl f Ar tempfile
.Op Fl n
.Op Fl cd Li \&| Fl r
.Op Fl v
.Ar disk
.Nm disklabel
.Fl R
.Op Fl r
.Op Fl n
.Op Fl v
.Ar disk Ar protofile
.Nm disklabel
.Op Fl NW
.Op Fl n
.Op Fl v
.Ar disk
.Pp
.Nm disklabel
.Fl B
.Op Fl n
.Op Fl v
.Oo
.Fl b Ar boot1
.Op Fl s Ar boot2
.Oc
.Ar disk
.Oo Ar disktype Oc
.Nm disklabel
.Fl w
.Fl B
.Op Fl n
.Op Fl v
.Oo
.Fl b Ar boot1
.Op Fl s Ar boot2
.Oc
.Ar disk Ar disktype
.Oo Ar packid Oc
.Nm disklabel
.Fl R
.Fl B
.Op Fl n
.Op Fl v
.Oo
.Fl b Ar boot1
.Op Fl s Ar boot2
.Oc
.Ar disk Ar protofile
.Oo Ar disktype Oc
.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 (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
The options are as follows:
.Bl -tag -width Ds
.It Fl n
Make no permanent changes to the disklabel (useful for debugging
purposes).
.It Fl v
Print additional information during operation (verbose mode).
.It Fl r
Causes the label to be read from or written to the disk directly,
rather than going through the system's in-core copy of the label.
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.
This flag does not work on a number of architectures, thus it is
not considered the right way to put a new label on a disk.
Its use is discouraged.
.It Fl B
Install bootstrap code.
The
.Fl r
flag is implied by
.Fl B
and never needs to be specified.
.It Fl b
Specify the single level boot program, or the primary boot program,
depending on the system boot architecture (single or two-level).
.It Fl s
On machines with a two-level bootstrap (such as i386-based systems),
specify the secondary boot program.
.It Fl d
Use the
.Em default
label.
This ignores any existing
.Ox
partitions on the disk.
Note that this option will only work for disks
that are capable of reporting their geometry, such as SCSI, IDE, and ESDI.
May not be used in conjunction with the
.Fl r
flag.
.It Fl c
Clear the system's in-core copy of the label and update it based on
the on-disk label.
May not be used in conjunction with the
.Fl r
flag.
.It Fl f Ar tempfile
Write entries to
.Ar tempfile
in
.Xr fstab 5
format for any partitions for which mount point information has been
specified.
The
.Fl f
flag is only valid when used in conjunction with the
.Fl E
flag.
If
.Ar tempfile
already exists, it will be overwritten.
.It Fl t
Format the label as a
.Xr disktab 5
entry.
.It Fl w
Write a standard label on the designated drive.
.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 E
Use a simple initial label editor, using the command-driven built-in
editor described below.
.It Fl R
Restore a disk label that was formatted in a prior operation and
saved in an
.Tn ASCII
file.
.It Fl N
Disallow writing of the pack label area on the selected disk.
.It Fl W
Allow writing of the pack label area on the selected disk.
.El
.Pp
The first form of the command (read) is used to examine the label on
the named disk drive (e.g., sd0 or
.Pa /dev/rsd0c Ns ).
It will display all of the parameters associated with the drive
and its partition layout.
Unless the
.Fl r
flag is given, 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 (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.
If the
.Fl r
flag is given, the disk sectors containing the label and bootstrap
will be written directly.
A side-effect of this is that any existing
bootstrap code will be overwritten and the disk rendered unbootable.
If
.Fl r
is not specified, the existing label will be updated via the in-core
copy and any bootstrap code will be unaffected.
If the disk does not already have a label, the
.Fl r
flag must be used.
In either case, the kernel's in-core label is replaced.
.Pp
In the third form of the command (edit), the label is read from the
in-core kernel copy, or directly from the disk if the
.Fl r
flag is also given.
The label is formatted 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.
Existing bootstrap code is unchanged regardless of whether
.Fl r
was specified.
.Pp
The initial label editor mode is only intended for new disks as it
will move partitions around as necessary to maintain a contiguous pool
of free blocks.
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,
and
.Sq g
for gigabytes.
Quantities will be rounded to the nearest
cylinder when units are specified for sizes (or offsets).
Commands may be aborted by entering
.Ql ^D
(Control-D).
Entering
.Ql ^D
at the main
.Ql >
prompt will exit the editor.
At prompts that request a size,
.Ql *
may be entered to indicate the rest of the available space.
The editor commands are as follows:
.Bl -tag -width "p [unit] "
.It ? Op command
Display help message with all available commands.
You may specify a
.Em command
for which to get more detailed help.
There is also (simple) context-sensitive help available at most prompts.
.It M
Display this manual page.
.It u
Undo (or redo) last change.
Entering
.Em u
once will undo your last change.
Entering it again will restore the change.
.It p Op unit
Print the current disk label.
If a
.Em unit
is given, the size and offsets are displayed in terms of the
specified unit.
.It e
Edit drive parameters.
This option is used to set the following
parameters: sectors/track, tracks/cylinder, sectors/cylinder,
number of cylinders on the disk, total sectors on the disk, rpm,
interleave, disk type, and a descriptive label string.
.It 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 fdisk 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 (minus
the starting sector).
This is useful for disks larger than 8
gigabytes where the fdisk partition table is incapable of storing
the real size.
.It r
Recalculate free space.
This option should really not be necessary under normal circumstances.
.It a Op part
Add new partition.
This option adds a new BSD partition.
If no partition letter is specified (a-p), the user will be prompted for
one.
.It c Op 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 d Op part
Delete an existing partition (or
.Ql *
to delete all partitions).
If no partition is specified, the user will be prompted for one.
You may not delete the
.Ql c
partition.
.It g Op d|b|u
Set disk geometry based on what the
.Em disk ,
.Em BIOS ,
or
.Em user
thinks (the
.Em user
geometry is simply what the label said before
.Nm
made any changes).
.It D
Sets the disk label to the default values as reported by the kernel.
This similates the case where there is no disk label.
.It m Op 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, block fragment size, block size, and cylinders per group for
the specified partition (not all parameters are configurable for
non-BSD partitions).
.It n Op 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 s Op path
Save the label to a file in
.Tn ASCII
format (suitable for loading via
the
.Fl R
option).
If no path is specified, the user will be prompted for one.
.It w
Write the label to disk.
This option will commit any changes to the on-disk label.
.It 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 x
Exit the editor without saving any changes to the label.
.It X
Toggle
.Dq expert mode .
By default, some settings are reserved for experts only (such as the
block and fragment size on ffs partitions).
.It z
Zeroes out the existing partition table, leaving only the
.Dq c
partition.
The drive parameters are not changed.
.El
.Pp
In the restore form of the command, 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.
As with
.Fl w ,
any existing bootstrap code will be clobbered if
.Fl r
is specified and will be unaffected otherwise.
.Pp
The final three forms of
.Nm
are used to install bootstrap code on machines where the bootstrap is
part of the label.
The bootstrap code is comprised of one or two boot
programs depending on the machine.
.Pp
When installing bootstrap code with the
.Fl B
flag, if the names are not explicitly given, standard boot programs
will be used.
The boot programs are located in
.Pa /usr/mdec .
The names of the programs are taken from the
.Dq b0
and
.Dq b1
parameters of the
.Xr disktab 5
entry for the disk if
.Ar disktype
was given and its disktab entry exists and includes those parameters.
Otherwise, boot program names are derived from the name of the
disk.
These names are of the form
.Pa basename Ns boot
for the primary (or only) bootstrap, and
.Pf boot Pa basename
for the secondary bootstrap; for example,
.Pa /usr/mdec/sdboot
and
.Pa /usr/mdec/bootsd
if the disk device is
.Em sd0 .
.Pp
The first of the three boot-installation forms is used to install
bootstrap code without changing the existing label.
It is essentially
a read command with respect to the disk label itself and all options
are related to the specification of the boot program as described
previously.
The final two forms are analogous to the basic write and
restore versions except that they will install bootstrap code in
addition to a new label.
.Pp
Note that when a disk has no real BSD 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 architechture.
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 non-OpenBSD
partitions will not be present in the default label, though you
may update them by hand.
To see the default label, run
.Nm
with the
.Fl d
flag.
You can then run
.Nm
with the
.Fl e
flag and paste any entries you want from the default label into the real
one.
.Sh EXAMPLES
.Dl disklabel sd0
.Pp
Display the in-core label for sd0 as obtained via
.Pa /dev/rsd0c .
.Pp
.Dl disklabel -w -r /dev/rsd0c sd2212 foo
.Pp
Create a label for sd0 based on information for
.Dq sd2212
found in
.Pa /etc/disktab .
Any existing bootstrap code will be clobbered.
(Normally you do not want to use the
.Fl r
flag though.)
.Pp
.Dl disklabel -e -r sd0
.Pp
Read the on-disk label for sd0, edit it and reinstall in-core as
well as on-disk.
(Normally you do not want to use the
.Fl r
flag
though.)
Existing bootstrap code is unaffected.
.Pp
.Dl disklabel -R sd0 mylabel
.Pp
Restore the on-disk and in-core label for sd0 from information in
.Pa mylabel .
Existing bootstrap code is unaffected.
.Pp
.Dl disklabel -B sd0
.Pp
Install a new bootstrap on sd0.
The boot code comes from
.Pa /usr/mdec/sdboot
and possibly
.Pa /usr/mdec/bootsd .
On-disk and in-core labels are unchanged, but on some systems other
information may be destroyed.
Use with care.
.Pp
.Dl disklabel -w -B /dev/rsd0c -b newboot sd2212
.Pp
Install a new label and bootstrap.
The label is derived from disktab information for
.Dq sd2212
and installed both in-core and
on-disk.
The bootstrap code comes from the file
.Pa /usr/mdec/newboot .
.Sh FILES
.Bl -tag -width Pa -compact
.It Pa /etc/disktab
.It Pa /usr/mdec/ Ns Em xx Ns boot
.It Pa /usr/mdec/boot Ns Em xx
.El
.Sh SEE ALSO
.Xr disklabel 5 ,
.Xr disktab 5 ,
.Xr scan_ffs 5
.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.
.Pp
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
.Dq bootable
disk.
When installing bootstrap code,
.Nm
checks for these cases.
If the installed boot code would overlap a partition of type
.Dv FS_UNUSED
it is marked as type
.Dv FS_BOOT .
The
.Xr newfs 8
utility will disallow creation of filesystems on
.Dv FS_BOOT
partitions.
Conversely, if a partition has a type other than
.Dv FS_UNUSED
or
.Dv FS_BOOT ,
.Nm
will not install bootstrap code that overlaps it.
.Sh NOTES
On i386 machines,
.Xr installboot 8
is normally used to install boot code.
The
.Fl B
option to
.Nm
can still be used to install old style boot code,
but this usage is deprecated.
.Pp
On some machines, such as the sparc and amiga, partition tables
may not exhibit the full functionality that is described above.
.Sh BUGS
When a disk name is given without a full pathname, the constructed
device name uses the
.Sq a
partition on the tahoe, the
.Sq c
partition on all others.
In
.Fl E
mode,
.Nm
is far too quick to shuffle partitions around; it should keep a
free block list and only move partitions around with the user's
permission.
Also, in
.Fl E
mode, partitions outside the
.Ox
portion of the disk should be changeable.