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

     bsdlabel — read and write BSD label

     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

     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

     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 forces bsdlabel to use a layout suitable for a
     different architecture.  Current valid values are i386, amd64, ia64,
     pc98, and alpha.  If this option is omitted, bsdlabel will use a layout
     suitable for the current machine.

   Reading the Disk Label
     To examine the label on a disk drive, use the form

     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, or if the type is specified as 'auto', 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.

   Restoring a Disk Label From a File
     To restore a disk label from a file, use the form

     bsdlabel -R [-An] [-m machine] disk protofile

     The bsdlabel utility is capable of restoring a disk label that was previ‐
     ously saved in a file in ASCII format.  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.

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

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

     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	     16	   4.2BSD     2048 16384  5128
	   b:  1091994	  81936	     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
	 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	     16	   4.2BSD     1024  8192    16
	   b:	160000	  81936	     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

     #	     The partition identifier is a single letter in the range ‘a’ to
	     ‘h’.  By convention, partition ‘c’ is reserved to describe the
	     entire disk.

     size    The size of the partition in sectors, K (kilobytes - 1024), M
	     (megabytes - 1024*1024), G (gigabytes - 1024*1024*1024), % (per‐
	     centage of free space after removing any fixed-size partitions
	     other than partition ‘c’), or * (all remaining free space after
	     fixed-size and percentage partitions).  For partition ‘c’, a size
	     of * indicates the entire disk.  Lowercase versions of suffixes
	     K, M, and G are allowed.  Size and suffix should be specified
	     without any 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.  The first partition should start at offset 16,
	     because the first 16 sectors are reserved for metadata.

     fstype  Describes the purpose of the partition.  The above 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 file systems only, the fragment size; see newfs(8).

     bsize   For 4.2BSD file systems only, the block size; see newfs(8).

	     For 4.2BSD file systems, the number of cylinders in a cylinder
	     group; see newfs(8).

     Display the label for the first slice of the da0 disk, as obtained via

	   bsdlabel da0s1

     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 da0s1 > savedlabel

     Create a label for da0s1:

	   bsdlabel -w /dev/da0s1

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

	   bsdlabel -e 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
     or on-disk:

	   bsdlabel -e -n da0s1

     Write a default label on da0s1.  Use another bsdlabel -e command to edit
     the partitioning and file system information:

	   bsdlabel -w da0s1

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

	   bsdlabel -R da0s1 savedlabel

     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 -R -n da0s1 label_layout

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

	   bsdlabel -B da0s1

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

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

	   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

     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 ad0s1 new_label_file”:

	 # /dev/ad0s1:

	 8 partitions:
	 #	  size	 offset	   fstype   [fsize bsize bps/cpg]
	   a:	400M	   16	 4.2BSD	    4096 16384	  75	 # (Cyl.    0 - 812*)
	   b:	  1G	    *	   swap
	   c:	   *	    *	 unused
	   e: 204800	    *	 4.2BSD
	   f:	  5g	    *	 4.2BSD
	   g:	   *	    *	 4.2BSD

     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.

     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 gpart(8).

     The various BSDs all use slightly different versions of BSD labels and
     are not generally compatible.

     ccd(4), geom(4), md(4), disktab(5), boot0cfg(8), fdisk(8), gpart(8),

BSD			       December 8, 2007				   BSD

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