DISKLABEL(8)						      System Manager'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 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.

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 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.

SEE ALSO

       disktab(5), disklabel(5)

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 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.

BUGS

       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)