BSD 2.11 - man page for disklabel (bsd section 8)

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DISKLABEL(8)									     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 parti-
       tions 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 (dis-
       play), 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 spe-
       cific effect of -r is described under each command.  The read and install forms also  sup-
       port 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
       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  describ-
       ing  each, or to edit the label after installation as described below.  The optional argu-
       ment 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 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.  If -r is not speci-
       fied, 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 newline.	As with -w , any existing bootstrap code  will	be  clob-
       bered 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 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.

       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.


	    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.  Exist-
       ing bootstrap code is unaffected.

	    disklabel -R ra0 mylabel

       Restore the on-disk and in-core label for sd0 from information in mylabel.  Existing boot-
       strap 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

       disktab(5), disklabel(5)

       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.

       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)
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