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

NAME
     disklabel -- read and write disk pack label

SYNOPSIS
     disklabel [-CFrt] disk
     disklabel -w [-] [-f disktab] disk disktype [packid]
     disklabel -e [-CFIr] disk
     disklabel -i [-FIr] disk
     disklabel -R [-] disk protofile
     disklabel [-NW] disk

     disklabel -B [-F] [-f disktab] [-b boot1 [-s boot2]] disk [disktype]
     disklabel -w -B [-F] [-f disktab] [-b boot1 [-s boot2]] disk disktype
               [packid]
     disklabel -R -B [-F] [-f disktab] [-b boot1 [-s boot2]] 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 boot-
     strap 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.  Any special effects of the
     -r flag are described with the affected commands.

     The -F option indicates that disklabel should treat disk as if it is a
     regular file, instead of as if it is a block device, for the purposes of
     reading and writing a disklabel.

     The -I option is similar to the -r option but provides defaults instead
     of failing with an error, if there is no existing disklabel on the disk.

     The read and install forms also support the -B option to install boot-
     strap code on some platforms, e.g., hp300, vax, and arm32.  The -B option
     is not supported on all platforms.  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., sd0 or /dev/rsd0c).  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 dis-
     played; 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.  If the -t flag is given, then the label will be
     formatted as a disktab(5) entry.

     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 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 con-
     tains blanks.  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 alternate disktab(5) file may be specified with the -f disktab option.

     An existing disk label may be edited by using the -e flag.  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.

     Labels can also created interactively using the -i flag.

     The -C flag causes the partition offset and size values to be displayed
     in <cylinder/track/sector> format.  Note that, regardless of whether -C
     was specified, this format is always accepted by disklabel on input with
     either the -e or -R flag.

     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 pro-
     duced when reading or editing a label.  Comments are delimited by # and
     newline.

     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
     composed of one or two boot programs depending on the machine.  The -B
     option is used (on some platforms only, see above) to denote that boot-
     strap 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 and -s flags.  On machines with only a single level
     of boot program, -b is the name of that program.  For machines with a
     two-level bootstrap, -b indicates the primary boot program and -s the
     secondary boot program.  If the names are not explicitly given, standard
     boot programs will be used.  The boot programs are located in /usr/mdec.
     The names of the programs are taken from the ``b0'' and ``b1'' parameters
     of the disktab(5) entry for the disk if disktype was given and its disk-
     tab entry exists and includes those parameters.  Otherwise, boot program
     names are derived from the name of the disk.  These names are of the form
     basenameboot for the primary (or only) bootstrap, and bootbasename for
     the secondary bootstrap; for example, /usr/mdec/sdboot and
     /usr/mdec/bootsd if the disk device is sd0.

     The first of the three boot-installation forms is used to install boot-
     strap 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.

FILES
     /etc/disktab
     /usr/mdec/xxboot
     /usr/mdec/bootxx

EXAMPLES
           disklabel sd0

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

           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.  Any existing bootstrap
     code will be clobbered.  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 &gt; protofile),
     editing the file, and replacing the label with disklabel -R sd0
     protofile.

           disklabel -e -r sd0

     Read the on-disk label for sd0, edit it and reinstall in-core as well as
     on-disk.  Existing bootstrap code is unaffected.

           disklabel -e -I sd0

     As previous, but don't fail if there was no label on the disk yet; pro-
     vide some default values instead.

           disklabel -i -I sd0

     As previous, only use the built-in interactive editor.

           disklabel -R sd0 mylabel

     Restore the on-disk and in-core label for sd0 from information in
     mylabel.  Existing bootstrap code is unaffected.

           disklabel -B sd0

     Install a new bootstrap on sd0 (only for platforms which support the -B
     option, see above).  The boot code comes from /usr/mdec/sdboot and possi-
     bly /usr/mdec/bootsd.  On-disk and in-core labels are unchanged.

           disklabel -w -B /dev/rsd0c -b newboot sd2212

     Install a new label and bootstrap (on platforms which support the -B
     option, see above).  The label is derived from disktab information for
     ``sd2212'' and installed both in-core and on-disk.  The bootstrap code
     comes from the file /usr/mdec/newboot.

           disklabel -R -r sd0 <protofile>

     Install a new label and bootstrap on a disk, from a prototype label file.
     This is a good way to install a label on a previously unlabeled disk for
     which no entry appears in /etc/disktab, if you create the prototype file
     by dumping some other disk's label to a file and editing it appropriately
     (total size, partition offsets, types, etc.)

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 parti-
     tion 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.

     On some machines the bootstrap code may not fit entirely in the area
     allocated for it by some filesystems.  As a result, it may not be possi-
     ble to have filesystems on some partitions of a ``bootable'' disk.  When
     installing bootstrap code, disklabel checks for these cases.  If the
     installed boot code would overlap a partition of type FS_UNUSED it is
     marked as type FS_BOOT.  The newfs(8) utility will disallow creation of
     filesystems on FS_BOOT partitions.  Conversely, if a partition has a type
     other than FS_UNUSED or FS_BOOT, disklabel will not install bootstrap
     code that overlaps it.

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

BUGS
     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 there-
     fore cannot be booted from.

BSD                             March 18, 2004                             BSD