DISKLABEL(8) System Manager's Manual DISKLABEL(8)
disklabel - read and write disk pack label
disklabel -r disk
disklabel -w [ -r ] disk disktype [ packid ]
disklabel -e [ -r ] disk
disklabel -R [ -r ] disk protofile
disklabel [ -NW ] disk
disklabel -B [ -b boot ] disk [ disktype ]
disklabel -w -B [ -b boot ] disk disktype [ packid ]
disklabel -R -B [ -b boot ] disk protofile [ disktype ]
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. On some systems, disklabel can be used to
install bootstrap code as well. There are several forms of the command that read (display), install or edit the label on a disk. Each
form has an additional option, -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. 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. The specific effect of -r is
described under each command. The read and install forms also support the -B option to install bootstrap code. These variants are
The first form of the command (read) is used to examine the label on the named disk drive (e.g. ra0 or /dev/rra0a). It will display all of
the parameters associated with the drive and its partition layout. Unless the -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 -r flag is given, the label from the raw disk will be displayed rather than the in-core label.
The second form of the command, with the -w flag, is used to write a standard label on the designated drive. The required arguments to
disklabel are the drive to be labelled (e.g. sd0), and the drive type as described in the disktab(5) file. The drive parameters and parti-
tions 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 -r flag is given, the disk sec-
tors containing the label and bootstrap will be written directly. A side-effect of this is that any existing bootstrap code will be over-
written and the disk rendered unbootable. If -r is not specified, the existing label will be updated via the in-core copy and any boot-
strap code will be unaffected. If the disk does not already have a label, the -r flag must be used. In either case, the kernel's in-core
label is replaced.
An existing disk label may be edited by using the -e flag. The label is read from the in-core kernel copy, or directly from the disk if
the -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, vi(1) is used. When the editor terminates, the formatted label is reread and used to rewrite the disk label. Exist-
ing bootstrap code is unchanged regardless of whether -r was specified.
With the -R flag, 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 delim-
ited by # and newline. As with -w , any existing bootstrap code will be clobbered if -r is specified and will be unaffected otherwise.
The -NW flags for disklabel explicitly disallow and allow, respectively, writing of the pack label area on the selected disk.
The final three forms of disklabel 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. The -B option is used to denote that bootstrap code is to be
installed. The -r flag is implied by -B and never needs to be specified. The name of the boot program(s) to be installed can be selected
in a variety of ways. First, the names can be specified explicitly via the -b flag. If the name is not explicitly given, standard boot
blocks will be used. The boot programs are located in /mdec. The names of the program is taken from the ``b0'' parameter of the disk-
tab(5) entry for the disk if disktype was given and its disktab entry exists and includes that parameter. Otherwise, the boot program name
is derived from the name of the disk. These name is of the form basenameuboot ; for example, /usr/mdec/rauboot if the disk device is ra0.
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 previ-
ously. 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.
Display the in-core label for ra0 as obtained via /dev/rra0a.
disklabel -w -r /dev/rra0a ra81x foo
Create a label for sd0 based on information for ``ra81x'' found in /etc/disktab. Any existing bootstrap code will be clobbered.
disklabel -e -r ra0
Read the on-disk label for ra0, edit it and reinstall in-core as well as on-disk. Existing bootstrap code is unaffected.
disklabel -R ra0 mylabel
Restore the on-disk and in-core label for sd0 from information in mylabel. Existing bootstrap code is unaffected.
disklabel -B ra0
Install a new bootstrap on ra0. The boot code comes from /mdec/rauboot. On-disk and in-core labels are unchanged.
disklabel -w -B /dev/rra0a -b newboot ra81x
Install a new label and bootstrap. The label is derived from disktab information for ``ra81x'' and installed both in-core and on-disk.
The bootstrap code comes from the file /mdec/newboot.
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 writ-
ten 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.
When a disk name is given without a full pathname, the constructed device name uses the ``a'' partition on the tahoe and pdp-11 the ``c''
partition on all others.
3rd Berkeley Distribution April 21, 1995 DISKLABEL(8)