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BSDLABEL(8)		FreeBSD	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 la-
     bel.  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 in-
     stead 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 and	amd64.	If
     this option is omitted, bsdlabel will use a layout	suitable for the cur-
     rent 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 ed-
     itor 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 al-
     lotted 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
	   gpart create	-s MBR da0
	   gpart add -t	freebsd	da0
	   gpart set -a	active -i 1 da0
	   gpart bootcode -b /boot/mbr 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 ada0s1 new_label_file":

	 # /dev/ada0s1:

	 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 uint32_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), gpart(8),	newfs(8)

     The disklabel utility appeared in 4.3BSD-Tahoe.

FreeBSD	13.0			October	5, 2016			  FreeBSD 13.0


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