FreeBSD Man Pages

disklabel(8)

NAME

     bsdlabel -- read and write disk pack label

SYNOPSIS

     bsdlabel [-A] disk | -f file
     bsdlabel -w [-An] [-B [-b boot]] [-m machine] disk | -f file [type]
     bsdlabel -e [-An] [-B [-b boot]] [-m machine] disk | -f file
     bsdlabel -R [-An] [-B [-b boot]] [-m machine] [-f] disk | -f file
	      protofile

DESCRIPTION

     The bsdlabel utility installs, examines or modifies the BSD label on a
     disk partition, or on a file containing a partition image.  In addition,
     bsdlabel can install bootstrap code.

   Disk Device Name
     When specifying the device (i.e., when the -f option is not used), the
     /dev/ path prefix may be omitted; the bsdlabel utility will automatically
     prepend it.

   General Options
     The -A option enables processing of the historical parts of the BSD
     label.  If the option is not given, suitable values are set for these
     fields.

     The -f option tells bsdlabel that the program will operate on a file
     instead of a disk partition.

     The -n option stops the bsdlabel program right before the disk would have
     been modified, and displays the result instead of writing it.

     The -m machine argument instructs bsdlabel to use the layout suitable for
     the specified machine.

   Reading the Disk Label
     To examine the label on a disk drive, use bsdlabel without options:

     bsdlabel [-A] [-m machine] disk

     disk represents the disk in question, and may be in the form da0 or
     /dev/da0.	It will display the partition layout.

   Writing a Standard Label
     To write a standard label, use the form

     bsdlabel -w [-An] [-m machine] disk [type]

     If the drive type is specified, the entry of that name in the disktab(5)
     file is used; otherwise a default layout is used.

   Editing an Existing Disk Label
     To edit an existing disk label, use the form

     bsdlabel -e [-An] [-m machine] disk

     This command opens the disk label in the default editor, and when the
     editor exits, the label is validated and if OK written to disk.
     should be in the same format as that produced when reading or editing a
     label.  Comments are delimited by `#' and newline.

   Installing Bootstraps
     If the -B argument is specified, bootstrap code will be read from the
     file /boot/boot and written to the disk.  The -b boot argument allows a
     different file to be used.

FILES

     /boot/boot    Default boot image.
     /etc/disktab  Disk description file.

SAVED FILE FORMAT

     The bsdlabel utility uses an ASCII version of the label when examining,
     editing, or restoring a disk label.  The format is:

	 8 partitions:
	 #	  size	 offset    fstype   [fsize bsize bps/cpg]
	   a:	 81920	      0    4.2BSD     1024  8192    16
	   b:	160000	  81920      swap
	   c:  1173930	      0    unused	 0     0	 # "raw" part, don't edit

     If the -A option is specified, the format is:

	 # /dev/da1c:
	 type: SCSI
	 disk: da0s1
	 label:
	 flags:
	 bytes/sector: 512
	 sectors/track: 51
	 tracks/cylinder: 19
	 sectors/cylinder: 969
	 cylinders: 1211
	 sectors/unit: 1173930
	 rpm: 3600
	 interleave: 1
	 trackskew: 0
	 cylinderskew: 0
	 headswitch: 0		 # milliseconds
	 track-to-track seek: 0  # milliseconds
	 drivedata: 0

	 8 partitions:
	 #	  size	 offset    fstype   [fsize bsize bps/cpg]
	   a:	 81920	      0    4.2BSD     1024  8192    16
	   b:	160000	  81920      swap
	   c:  1173930	      0    unused	 0     0	 # "raw" part, don't edit

     Lines starting with a `#' mark are comments.

     The partition table can have up to 8 entries.  It contains the following
     information:

     #	     The partition identifier is a single letter in the range `a' to
	     `h'.  By convention, partition `c' is reserved to describe the
	     entire disk.
	     spaces between them.

	     Example: 2097152, 1G, 1024M and 1048576K are all the same size
	     (assuming 512-byte sectors).

     offset  The offset of the start of the partition from the beginning of
	     the drive in sectors, or * to have bsdlabel calculate the correct
	     offset to use (the end of the previous partition plus one, ignor-
	     ing partition `c'.  For partition `c', * will be interpreted as
	     an offset of 0.

     fstype  Describes the purpose of the partition.  The example shows all
	     currently used partition types.  For UFS file systems and ccd(4)
	     partitions, use type 4.2BSD.  For Vinum drives, use type vinum.
	     Other common types are swap and unused.  By convention, partition
	     `c' represents the entire slice and should be of type unused,
	     though bsdlabel does not enforce this convention.	The bsdlabel
	     utility also knows about a number of other partition types, none
	     of which are in current use.  (See the definitions starting with
	     FS_UNUSED in <sys/disklabel.h> for more details.)

     fsize   For 4.2BSD and LFS file systems only, the fragment size.
	     Defaults to 1024 for partitions smaller than 1GB, 4096 for parti-
	     tions 1GB or larger.

     bsize   For 4.2BSD and LFS file systems only, the block size.  Defaults
	     to 8192 for partitions smaller than 1GB, 16384 for partitions 1GB
	     or larger.

     bps/cpg
	     For 4.2BSD file systems, the number of cylinders in a cylinder
	     group.  For LFS file systems, the segment shift value.  Defaults
	     to 16 for partitions smaller than 1GB, 64 for partitions 1GB or
	     larger.

EXAMPLES

	   bsdlabel da0s1

     Display the label for the first slice of the da0 disk, as obtained via
     /dev/da0s1.

	   bsdlabel da0s1 > savedlabel

     Save the in-core label for da0s1 into the file savedlabel.  This file can
     be used with the -R option to restore the label at a later date.

	   bsdlabel -w /dev/da0s1

     Create a label for da0s1.

	   bsdlabel -e da0s1

     Read the label for da0s1, edit it, and install the result.

	   bsdlabel -e -n da0s1

     Read the on-disk label for da0s1, edit it, and display what the new label
     would be (in sectors).  It does not install the new label either in-core

     Restore the on-disk and in-core label for da0s1 from information in
     savedlabel.

	   bsdlabel -R -n da0s1 label_layout

     Display what the label would be for da0s1 using the partition layout in
     label_layout.  This is useful for determining how much space would be
     allotted for various partitions with a labeling scheme using %-based or *
     partition sizes.

	   bsdlabel -B da0s1

     Install a new bootstrap on da0s1.	The boot code comes from /boot/boot.

	   bsdlabel -w -B -b newboot /dev/da0s1

     Install a new label and bootstrap.  The bootstrap code comes from the
     file newboot in the current working directory.

	   dd if=/dev/zero of=/dev/da0 bs=512 count=32
	   fdisk -BI da0
	   dd if=/dev/zero of=/dev/da0s1 bs=512 count=32
	   bsdlabel -w -B da0s1
	   bsdlabel -e da0s1

     Completely wipe any prior information on the disk, creating a new
     bootable disk with a DOS partition table containing one slice, covering
     the whole disk.  Initialize the label on this slice, then edit it.  The
     dd(1) commands are optional, but may be necessary for some BIOSes to
     properly recognize the disk.

     This is an example disk label that uses some of the new partition size
     types such as %, M, G, and *, which could be used as a source file for
     ``bsdlabel -R ad0s1c new_label_file'':

	 # /dev/ad0s1c:

	 8 partitions:
	 #	  size	 offset    fstype   [fsize bsize bps/cpg]
	   a:	400M	    0	 4.2BSD     4096 16384	  75	 # (Cyl.    0 - 812*)
	   b:	  1G	    *	   swap
	   c:	   *	    *	 unused
	   e: 204800	    *	 4.2BSD
	   f:	  5g	    *	 4.2BSD
	   g:	   *	    *	 4.2BSD

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.

COMPATIBILITY

     Due to the use of an u_int32_t to store the number of sectors, BSD labels
     are restricted to a maximum of 2^32-1 sectors.  This usually means 2TB of
     disk space.  Larger disks should be partitioned using another method such
     as gpt(8).  The various BSDs all use slightly different versions of BSD
     labels and are not generally compatible.

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