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NetBSD 6.1.5 - man page for disklabel (netbsd section 8)

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DISKLABEL(8)			   BSD System Manager's Manual			     DISKLABEL(8)

NAME
     disklabel -- read and write disk pack label

SYNOPSIS
     disklabel [-ACDFrtv] disk
     disklabel -e [-CDFIrv] disk
     disklabel -i [-DFIrv] disk
     disklabel -R [-DFrv] disk protofile
     disklabel -w [-DFrv] [-f disktab] disk disktype [packid]
     disklabel [-NW] disk
     disklabel -l

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 parti-
     tions on the drive, or to replace a damaged label.

     The -e, -i, -l, -R, -w, -N, and -W options determine the basic operation.	If none are spec-
     ified the label is displayed.

     -e    Edit the existing label (using EDITOR) and write it back to the disk.  If EDITOR is
	   undefined, then vi(1) is used.

     -i    Interactively update the existing label and write it back to the disk.

     -l    Show all known file system types (those that can be specified along a partition within
	   the label) and exit.

     -R    Write (restore) a label by reading it from protofile.  The file should be in the same
	   format as the default output.

     -w    Write a standard label for the specified disktype.  See disktab(5).

     -N    Disallow writes to the disk sector that contains the label.	This is the default
	   state.

     -W    Allow writes to the disk sector that contains the label.  This state may not persist
	   if no programs have the disk open.

     The majority of the rest of the options affect more than one form of the command:

     -A    Read all labels from the disk, including ones deleted with disklabel -D.  Implies -r.

     -C    Output the partition offset and size values in <cylinder/head/sector> format.  Note
	   this format is always accepted on input with either the -e or -R flags.

     -D    Delete all existing labels (by 1's complementing the magic number) before writing any
	   labels to their default location.  Implies -r.  If -D is specified without a request
	   to write the label, then existing labels are just deleted.

     -F    Treat disk as a regular file.  This suppresses all ioctl(2) calls, and is the default
	   if disk is a regular file.  disk is always opened using opendisk(3) even if -F is
	   specified.  Implies -r.

     -I    If a label cannot be read from disk request the default one from the kernel.  Implies
	   -r.

     -f disktab
	   Specify the name of a file to use instead of /etc/disktab.

     -r    Read/write the disk directly rather than using ioctl(2) requests on the kernel.  When
	   writing a label, the kernel will be told about the label before the label is written
	   and asked to write afterwards.  This is the historic behaviour and can be supressed by
	   specifying -F.

     -t    Format the output as a disktab(5) entry.

     -v    Be verbose about the operations being done, in particular the disk sectors being read
	   and written.  Specifying -v more than once will increase the verbosity.

     On systems that expect to have disks with MBR partitions (see fdisk(8)) disklabel will find,
     and update if requested, labels in the first 8k of type 169 (NetBSD) MBR labels and within
     the first 8k of the physical disk.  On other systems disklabel will only look at the start
     of the disk.  The offset at which the labels are written is also system dependent.

     disklabel will detect byteswapped labels, but currently cannot display them.

     Previous versions of disklabel could update the bootstrap code on some architectures.  This
     functionality has been subsumed by installboot(8).

FILES
     /etc/disktab

EXIT STATUS
     The exit status of disklabel is set to indicate any errors or warnings.  The values used
     are:

     0	     The disklabel utility has completed successfully.

     1	     A fatal error has occurred, such as unknown options passed on the command line, or
	     writing the disklabel failed.

     4	     An I/O error of some sort occurred.

     101..n  One or more warnings occured while reading the disklabel.	Subtract 100 to get the
	     number of warnings detected.

EXAMPLES
	   disklabel sd0

     Display the in-core label for sd0 as obtained via /dev/rsd0c.

	   disklabel -i -r sd0

     Read the on-disk label for sd0, edit it using the built-in interactive editor and reinstall
     in-core as well as on-disk.

	   disklabel -i -I sd0

     As previous, but don't fail if there was no label on the disk yet; provide some default val-
     ues instead.

	   disklabel -e -I sd0

     As previous, only edit using $EDITOR

	   disklabel -w -r /dev/rsd0c sd2212 foo

     Create a label for sd0 based on information for ``sd2212'' found in /etc/disktab, using foo
     as the disk pack label.  If you do not have an entry for your disk in /etc/disktab, you can
     use this style to put an initial label onto a new disk.  Then dump the label to a file
     (using disklabel sd0 > protofile), editing the file, and replacing the label with disklabel
     -R sd0 protofile.

	   disklabel -R sd0 mylabel

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

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.

SEE ALSO
     opendisk(3), disklabel(5), disktab(5), dkctl(8), fdisk(8), gpt(8), installboot(8),
     mbrlabel(8), mscdlabel(8)

BUGS
     The disklabel structure stored on disk cannot support partitions/disks greater than 2TB.
     Please use gpt(8) and dkctl(8) to manage partitions and disks larger than 2TB.

     If the disk partition is not specified in the disk name (i.e., xy0 instead of /dev/rxy0c),
     disklabel will construct the full pathname of the disk and use the ``d'' partition on i386,
     hpcmips, or arc, and the ``c'' partition on all others.

     On the sparc, sparc64, sun2, and sun3 NetBSD systems, the size of each partition must be a
     multiple of the number of sectors per cylinder (i.e., each partition must be an integer num-
     ber of cylinders), or the boot ROMs will declare the label invalid and fail to boot the sys-
     tem.

     In addition, the -r option should never be used on a sparc, sparc64, sun2, or sun3 system
     boot disk - the NetBSD kernel translates the NetBSD disk label into a SunOS compatible for-
     mat (which is required by the boot PROMs) when it writes the label.  Using the -r flag
     causes disklabel to write directly to disk, and bypass the format translation.  This will
     result in a disk label that the PROMs will not recognize, and that therefore cannot be
     booted from.

BSD					  July 25, 2011 				      BSD
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