.\" Copyright (c) 1987, 1988, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\" This code is derived from software contributed to Berkeley by
.\" Symmetric Computer Systems.
.\" %sccs.include.redist.roff%
.\" @(#)disklabel.8 8.2 (Berkeley) %G%
.Nd read and write disk pack label
can be used to install, examine or modify the label on a disk drive or pack.
When writing the label, it can be used
to change the drive identification,
the disk partitions on the drive,
or to replace a damaged label.
can be used to install bootstrap code as well.
There are several forms of the command that read (display), install or edit
Each form has an additional option,
which 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; it must be used when first installing a label on a disk.
is described under each command.
The read and install forms also support the
option to install bootstrap code.
These variants are described later.
The first form of the command (read) is used to examine the label on the named
disk drive (e.g. sd0 or /dev/rsd0c).
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.
flag is given, the label from the raw disk will be displayed rather
The second form of the command, with the
flag, is used to write a standard label on the designated drive.
The required arguments to
are the drive to be labelled (e.g. sd0), and
the drive type as described in the
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.
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.
the existing label will be updated via the in-core copy and any bootstrap
If the disk does not already have a label, the
In either case, the kernel's in-core label is replaced.
An existing disk label may be edited by using the
The label is read from the in-core kernel copy,
or directly from the disk if the
The label is formatted 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 regardless of whether
is capable of restoring a disk label that was formatted
in a prior operation and saved in an ascii file.
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
any existing bootstrap code will be clobbered if
is specified and will be unaffected otherwise.
allow, respectively, writing of the pack label area on the selected disk.
are used to install boostrap code on machines where the bootstrap is part
The bootstrap code is comprised of one or two boot programs depending on
option is used to denote that bootstrap code is to be installed.
and never needs to be specified.
The name of the boot program(s) to be installed can be selected in a
First, the names can be specified explicitly via the
On machines with only a single level of boot program,
is the name of that program.
For machines with a two-level bootstrap,
indicates the primary boot program and
the secondary boot program.
If the names are not explicitly given, standard boot programs will be used.
The boot programs are located in
The names of the programs are taken from the ``b0'' and ``b1'' parameters
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
for the primary (or only) bootstrap, and
for the secondary bootstrap;
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.
.Bl -tag -width Pa -compact
.It Pa /usr/mdec/ Ns Em xx Ns boot
.It Pa /usr/mdec/boot Ns Em xx
Display the in-core label for sd0 as obtained via
.Dl disklabel -w -r /dev/rsd0c sd2212 foo
Create a label for sd0 based on information for ``sd2212'' found in
Any existing bootstrap code will be clobbered.
Read the on-disk label for sd0, edit it and reinstall in-core as well
Existing bootstrap code is unaffected.
.Dl disklabel -R sd0 mylabel
Restore the on-disk and in-core label for sd0 from information in
Existing bootstrap code is unaffected.
Install a new bootstrap on sd0.
On-disk and in-core labels are unchanged.
.Dl disklabel -w -B /dev/rsd0c -b newboot sd2212
Install a new label and bootstrap.
The label is derived from disktab information for ``sd2212'' and
installed both in-core and on-disk.
The bootstrap code comes from the file
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
When installing bootstrap code,
If the installed boot code would overlap a partition of type FS_UNUSED
it is marked as type FS_BOOT.
utility will disallow creation of filesystems on FS_BOOT partitions.
Conversely, if a partition has a type other than FS_UNUSED or FS_BOOT,
will not install bootstrap code that overlaps it.
When a disk name is given without a full pathname,
the constructed device name uses the ``a'' partition on the tahoe,
the ``c'' partition on all others.