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.\"	@(#)disklabel.8	6.8 (Berkeley) 6/24/90
.\"
.TH DISKLABEL 8 "June 24, 1990"
.UC 5
.SH NAME
disklabel \- read and write disk pack label
.SH SYNOPSIS
.B disklabel
[
.B \-r
]
.I disk
.br
.B disklabel \-w
[
.B \-r
]
.I disk
.I disktype
[
.I packid
[
.I priboot secboot
] ]
.br
.B disklabel \-e
[
.B \-r
]
.I disk
.br
.B disklabel \-R
[
.B \-r
]
.I disk protofile
[
.I priboot secboot
]
.br
.B disklabel
[
.B \-NW
]
.I disk
.SH DESCRIPTION
.I Disklabel
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 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 (VAX 11/750),
the label is inserted into the bootstrap program.
This information is used by the system disk driver and by the bootstrap
program to determine how to program the drive.
There are several forms of the command that display, install or modify
the label on a disk.
Each form has an additional option,
.BR \-r ,
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.
When writing, the in-core copy is also updated if possible.
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.
.PP
The first form of the command is used to examine the label on the named
disk drive (e.g. hp0 or /dev/rhp0c).
It will display all of the parameters associated with the drive
and its partition layout.
Unless the
.B \-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.
If the
.B \-r
flag is given, the label from the raw disk will be displayed rather
than the in-core label.
.PP
The second form of the command, with the
.B \-w
flag, is used to write a standard label on the designated drive.
The required arguments to
.I disklabel
are the drive to be labelled (e.g. hp0), and
the drive type as described in the
.IR disktab (5)
file.
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 first optional argument is a pack identification string,
up to 16 characters long.
The pack id must be quoted if it contains blanks.
If the
.B \-r
flag is given, the disk sectors containing the label and bootstrap
will be written directly,
otherwise the existing label will be updated in place without modifying
the bootstrap.
If the disk does not already have a label, the
.B \-r
flag must be used.
In either case, the kernel's in-core label is replaced.
.PP
Alternate versions of the bootstrap files may be specified
after the pack identifier.
If an alternate bootstrap is not specified, the standard bootstrap will be used.
The bootstrap programs are located in
.IR /usr/mdec .
The names of the bootstrap programs may be specified in
.IR disktab (5);
if not specified,
the default names are of the form
.IR basename boot
for the primary (block 0) bootstrap, and
.RI boot basename
for the secondary (block 1-15) bootstrap;
for example, /usr/mdec/hpboot and /usr/mdec/boothp
if the disk device is
.BR hp0 .
.PP
An existing disk label may be edited by using the
.B \-e
flag.
The label is read from the in-core kernel copy,
or directly from the disk if the
.B \-r
flag is also given.
The label is formatted and then supplied to an editor for changes.
If no editor is specified in an EDITOR environment variable,
.IR vi (1)
is used.
When the editor terminates, the formatted label is reread
and used to rewrite the disk label.
.PP
With the
.B \-R
flag,
.I disklabel
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
.B #
and newline.
If the
.B \-r
option is also given,
a block-0 bootstrap is installed on machines that use one;
either the disktype or the names of the bootstrap files must be specified
on such machines.
.PP
Finally, the \fB-NW\fP flags for \fIdisklabel\fP explicitly disallow and
allow, respectively, writing of the pack label area on the selected disk.
.SH FILES
/etc/disktab
.br
/usr/mdec/\fIxx\fPboot
.br
/usr/mdec/boot\fIxx\fP
.SH "SEE ALSO"
disktab(5), disklabel(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 ``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.
.SH BUGS
When a disk name is given without a full pathname,
the constructed device name uses the ``c'' partition on the vax
and the ``a'' partition on the tahoe.