# 2.11BSD#431 - /usr/man/cat8/disklabel.0

    DISKLABEL(8)	    UNIX Programmer's Manual	     DISKLABEL(8)

    NAME
         disklabel - read and write disk pack label

    SYNOPSIS
         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 ]

    DESCRIPTION
         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
         described later.

         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 disk-
         tab(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

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    DISKLABEL(8)	    UNIX Programmer's Manual	     DISKLABEL(8)

         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 sectors contain-
         ing 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 -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 -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.  Existing
         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 delimited by # and new-
         line.  As with -w , any existing bootstrap code will be
         clobbered if -r is specified and will be unaffected other-
         wise.

         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 pro-
         gram is taken from the ``b0'' parameter of the disktab(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.

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    DISKLABEL(8)	    UNIX Programmer's Manual	     DISKLABEL(8)

         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 specifica-
         tion of the boot program as described previously.	The final
         two forms are analogous to the basic write and restore ver-
         sions except that they will install bootstrap code in addi-
         tion to a new label.

    FILES
         /etc/disktab
         /mdec/xxuboot

    EXAMPLES
    	  disklabel sd0

         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 unaf-
         fected.

    	  disklabel -R ra0 mylabel

         Restore the on-disk and in-core label for sd0 from informa-
         tion 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.

    SEE ALSO
         disktab(5), disklabel(5)

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    DISKLABEL(8)	    UNIX Programmer's Manual	     DISKLABEL(8)

    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'' par-
         tition 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.

    BUGS
         When a disk name is given without a full pathname, the con-
         structed device name uses the ``a'' partition on the tahoe
         and pdp-11 the ``c'' partition on all others.

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