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

     disklabel - read and write disk pack label

     disklabel [-ACDFmnrtv] [-B endian] [-L sector] [-M machine] [-O offset]
               [-P size] disk
     disklabel -e [-CDFImnrv] [-B endian] [-L sector] [-M machine] [-O offset]
               [-P size] disk
     disklabel -i [-DFImnrv] [-B endian] [-L sector] [-M machine] [-O offset]
               [-P size] disk
     disklabel -R [-DFmnrv] [-B endian] [-L sector] [-M machine] [-O offset]
               [-P size] disk protofile
     disklabel -w [-DFmnrv] [-B endian] [-L sector] [-M machine] [-O offset]
               [-P size] [-f disktab] disk disktype [packid]
     disklabel [-NW] disk
     disklabel -l

     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.

     The -e, -i, -l, -N, -R, -W, and -w options determine the basic operation.
     If none are specified 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

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

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

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

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

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

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

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

     -B endian
           Specify the byteorder of the label to be written.  It should be:
           "be" or "le".

     -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.

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

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

     -L sector
           Specify the relative sector number of the disklabel similar to the
           environment variable DISKLABELSECTOR.

     -M machine
           Specify the machine to generate a label for.  Defaults to the
           current machine it is compiled for.  Specific details can be
           overridden via environment and with the options -B, -L, -m, -n, -O,
           and -P.

     -m    Expect the label to have an MBR.

     -n    Expect the label not to have an MBR.

     -O offset
           Specify the relative byte offset of the disklabel similar to the
           environment variable DISKLABELOFFSET.

     -P size
           Specify the size of the partition table.

     -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 suppressed
           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

     disklabel will detect byteswapped labels, but currently cannot display

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


     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 occurred while reading the disklabel.
             Subtract 100 to get the number of warnings detected.

           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 do not fail if there was no label on the disk yet;
     provide some default values 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

     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.

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

     The disklabel utility appeared in 4.3BSD-Tahoe.

     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 number of cylinders), or the boot ROMs
     will declare the label invalid and fail to boot the system.

     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 format (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.

     The -m flag previously toggled between using an MBR and not using an MBR,
     with the default being implied by the machine type.  It now always
     enables MBR mode, independent of the machine default.  Use the -n flag to
     disable MBR mode.

NetBSD 10.99                     July 2, 2019                     NetBSD 10.99