Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages


home | help
MKE2FS(8)		    System Manager's Manual		     MKE2FS(8)

       mke2fs -	create an ext2/ext3/ext4 filesystem

       mke2fs [	-c | -l	filename ] [ -b	block-size ] [ -f fragment-size	] [ -g
       blocks-per-group	] [ -G number-of-groups	] [ -i bytes-per-inode ] [  -I
       inode-size ] [ -j ] [ -J	journal-options	] [ -N number-of-inodes	] [ -n
       ] [ -m reserved-blocks-percentage  ]  [	-o  creator-os	]  [  -O  fea-
       ture[,...]  ] [ -q ] [ -r fs-revision-level ] [ -E extended-options ] [
       -v ] [ -F ] [ -L	volume-label ] [ -M last-mounted-directory ] [ -S ]  [
       -t fs-type ] [ -T usage-type ] [	-U UUID	] [ -V ] device	[ blocks-count

       mke2fs -O journal_dev [ -b block-size ] [ -L volume-label ] [ -n	] [ -q
       ] [ -v ]	external-journal [ blocks-count	]

       mke2fs  is used to create an ext2, ext3,	or ext4	filesystem, usually in
       a disk partition.  device is the	special	file corresponding to the  de-
       vice  (e.g /dev/hdXX).  blocks-count is the number of blocks on the de-
       vice.  If omitted, mke2fs automagically figures the file	 system	 size.
       If  called  as  mkfs.ext3  a journal is created as if the -j option was

       The defaults of the parameters for the newly created filesystem,	if not
       overridden   by	the  options  listed  below,  are  controlled  by  the
       /etc/mke2fs.conf	configuration file.   See  the	mke2fs.conf(5)	manual
       page for	more details.

       -b block-size
	      Specify  the  size  of blocks in bytes.  Valid block-size	values
	      are 1024,	2048 and 4096 bytes per	block.	If omitted, block-size
	      is  heuristically	 determined by the filesystem size and the ex-
	      pected usage of the filesystem (see the -T option).   If	block-
	      size  is preceded	by a negative sign ('-'), then mke2fs will use
	      heuristics to determine the appropriate  block  size,  with  the
	      constraint  that	the  block  size  will	be at least block-size
	      bytes.  This is useful for certain hardware  devices  which  re-
	      quire that the blocksize be a multiple of	2k.

       -c     Check the	device for bad blocks before creating the file system.
	      If this option is	specified twice, then a	slower read-write test
	      is used instead of a fast	read-only test.

       -E extended-options
	      Set  extended  options for the filesystem.  Extended options are
	      comma separated, and may take an argument	using the equals ('=')
	      sign.   The  -E  option  used  to	 be  -R	in earlier versions of
	      mke2fs.  The -R option is	still accepted for backwards  compati-
	      bility.	The following extended options are supported:

			  Configure  the  filesystem  for  a  RAID  array with
			  stride-size filesystem blocks. This is the number of
			  blocks  read or written to disk before moving	to the
			  next disk, which is sometimes	 referred  to  as  the
			  chunk	  size.	  This	mostly	affects	 placement  of
			  filesystem metadata like bitmaps at mke2fs  time  to
			  avoid	 placing them on a single disk,	which can hurt
			  performance.	It may also be used by the block allo-

			  Configure  the  filesystem  for  a  RAID  array with
			  stripe-width filesystem blocks per stripe.  This  is
			  typically  stride-size * N, where N is the number of
			  data-bearing disks in	the  RAID  (e.g.  for  RAID  5
			  there	is one parity disk, so N will be the number of
			  disks	in the array minus 1).	This allows the	 block
			  allocator to prevent read-modify-write of the	parity
			  in a RAID stripe if possible when the	data is	 writ-

			  Reserve  enough  space  so  that the block group de-
			  scriptor table can grow to support a filesystem that
			  has max-online-resize	blocks.

		   lazy_itable_init[= _0 to disable, 1 to enable_]
			  If enabled and the uninit_bg feature is enabled, the
			  inode	table will not be fully	initialized by mke2fs.
			  This speeds up filesystem initialization noticeably,
			  but it requires the kernel  to  finish  initializing
			  the filesystem in the	background when	the filesystem
			  is first mounted.  If	the option value  is  omitted,
			  it defaults to 1 to enable lazy inode	table initial-

			  Set a	flag in	the filesystem	superblock  indicating
			  that	it  may	 be  mounted using experimental	kernel
			  code,	such as	the ext4dev filesystem.

			  Attempt to discard blocks at mkfs  time  (discarding
			  blocks  initially  is	 useful	on solid state devices
			  and sparse / thin-provisioned	storage). When the de-
			  vice	advertises  that discard also zeroes data (any
			  subsequent read after	the discard and	 before	 write
			  returns  zero),  then	 mark all not-yet-zeroed inode
			  tables  as  zeroed.  This  significantly  speeds  up
			  filesystem initialization. This is set as default.

			  Do  not attempt to discard blocks at mkfs time. This
			  is the default.

       -f fragment-size
	      Specify the size of fragments in bytes.

       -F     Force mke2fs to create a filesystem, even	if the	specified  de-
	      vice  is	not a partition	on a block special device, or if other
	      parameters do not	make sense.  In	order to force mke2fs to  cre-
	      ate  a filesystem	even if	the filesystem appears to be in	use or
	      is mounted (a truly dangerous thing to do), this option must  be
	      specified	twice.

       -g blocks-per-group
	      Specify  the number of blocks in a block group.  There is	gener-
	      ally no reason for the user to ever set this parameter,  as  the
	      default  is optimal for the filesystem.  (For administrators who
	      are creating filesystems on RAID arrays, it is preferable	to use
	      the  stride  RAID	parameter as part of the -E option rather than
	      manipulating the number of blocks	per group.)   This  option  is
	      generally	used by	developers who are developing test cases.

       -G number-of-groups
	      Specify  the number of block groups that will be packed together
	      to create	a larger virtual block group (or "flex_bg  group")  in
	      an  ext4	filesystem.  This improves meta-data locality and per-
	      formance on meta-data heavy workloads.   The  number  of	groups
	      must  be	a  power of 2 and may only be specified	if the flex_bg
	      filesystem feature is enabled.

       -i bytes-per-inode
	      Specify the bytes/inode ratio.  mke2fs creates an	inode for  ev-
	      ery  bytes-per-inode bytes of space on the disk.	The larger the
	      bytes-per-inode ratio, the fewer inodes will be  created.	  This
	      value  generally	shouldn't be smaller than the blocksize	of the
	      filesystem, since	in that	case more inodes would	be  made  than
	      can  ever	 be used.  Be warned that it is	not possible to	expand
	      the number of inodes on a	filesystem after it is created,	so  be
	      careful deciding the correct value for this parameter.

       -I inode-size
	      Specify  the  size  of  each  inode  in  bytes.	mke2fs creates
	      256-byte inodes by default.  In kernels after  2.6.10  and  some
	      earlier  vendor  kernels it is possible to utilize inodes	larger
	      than 128 bytes to	store extended attributes for improved perfor-
	      mance.   The  inode-size	value  must  be	a power	of 2 larger or
	      equal to 128.  The larger	the inode-size the more	space the  in-
	      ode table	will consume, and this reduces the usable space	in the
	      filesystem and can also negatively impact	performance.  Extended
	      attributes  stored  in  large  inodes are	not visible with older
	      kernels, and such	filesystems will not  be  mountable  with  2.4
	      kernels  at  all.	 It is not possible to change this value after
	      the filesystem is	created.

       -j     Create the filesystem with an ext3 journal.  If the -J option is
	      not  specified,  the  default journal parameters will be used to
	      create an	appropriately sized journal (given  the	 size  of  the
	      filesystem) stored within	the filesystem.	 Note that you must be
	      using a kernel which has ext3 support in order to	actually  make
	      use of the journal.

       -J journal-options
	      Create  the ext3 journal using options specified on the command-
	      line.  Journal options are comma separated, and may take an  ar-
	      gument  using the	equals ('=')  sign.  The following journal op-
	      tions are	supported:

			  Create an internal journal (i.e., stored inside  the
			  filesystem)  of  size	 journal-size  megabytes.  The
			  size of the journal must be at least 1024 filesystem
			  blocks  (i.e.,  1MB if using 1k blocks, 4MB if using
			  4k blocks, etc.)  and	may be no  more	 than  102,400
			  filesystem blocks.

			  Attach  the  filesystem  to the journal block	device
			  located on external-journal.	The  external  journal
			  must already have been created using the command

			  mke2fs -O journal_dev	external-journal

			  Note	that  external-journal	must have been created
			  with the same	block size as the new filesystem.   In
			  addition,  while there is support for	attaching mul-
			  tiple	filesystems to a single	external journal,  the
			  Linux	 kernel	and e2fsck(8) do not currently support
			  shared external journals yet.

			  Instead of specifying	a device name directly,	exter-
			  nal-journal  can  also  be  specified	 by either LA-
			  BEL=label or UUID=UUID to locate the external	 jour-
			  nal by either	the volume label or UUID stored	in the
			  ext2 superblock at the start of  the	journal.   Use
			  dumpe2fs(8) to display a journal device's volume la-
			  bel and UUID.	 See also the -L option	of tune2fs(8).

	      Only one of the size or  device  options	can  be	 given	for  a

       -l filename
	      Read  the	 bad  blocks  list from	filename.  Note	that the block
	      numbers in the bad block list must be generated using  the  same
	      block  size  as  used  by	mke2fs.	 As a result, the -c option to
	      mke2fs is	a much simpler and less	error-prone method of checking
	      a	disk for bad blocks before formatting it, as mke2fs will auto-
	      matically	pass the correct parameters to the badblocks program.

       -L new-volume-label
	      Set the volume label for	the  filesystem	 to  new-volume-label.
	      The maximum length of the	volume label is	16 bytes.

       -m reserved-blocks-percentage
	      Specify the percentage of	the filesystem blocks reserved for the
	      super-user.  This	avoids fragmentation,  and  allows  root-owned
	      daemons,	such  as syslogd(8), to	continue to function correctly
	      after non-privileged processes are prevented from	writing	to the
	      filesystem.  The default percentage is 5%.

       -M last-mounted-directory
	      Set  the	last mounted directory for the filesystem.  This might
	      be useful	for the	sake of	utilities that key  off	 of  the  last
	      mounted  directory  to  determine	where the filesystem should be

       -n     Causes mke2fs to not actually create a filesystem,  but  display
	      what it would do if it were to create a filesystem.  This	can be
	      used to determine	the location of	the backup superblocks	for  a
	      particular  filesystem,  so  long	 as the	mke2fs parameters that
	      were passed when the filesystem was originally created are  used
	      again.  (With the	-n option added, of course!)

       -N number-of-inodes
	      Overrides	 the  default calculation of the number	of inodes that
	      should be	reserved for the filesystem (which  is	based  on  the
	      number  of  blocks  and the bytes-per-inode ratio).  This	allows
	      the user to specify the number of	desired	inodes directly.

       -o creator-os
	      Overrides	the default value of the  "creator  operating  system"
	      field of the filesystem.	The creator field is set by default to
	      the name of the OS the mke2fs executable was compiled for.

       -O feature[,...]
	      Create a filesystem with	the  given  features  (filesystem  op-
	      tions), overriding the default filesystem	options.  The features
	      that are enabled by default are specified	by  the	 base_features
	      relation,	   either   in	 the   [defaults]   section   in   the
	      /etc/mke2fs.conf configuration file, or in the  [fs_types]  sub-
	      sections for the usage types as specified	by the -T option, fur-
	      ther modified by the features relation found in  the  [fs_types]
	      subsections  for	the  filesystem	 and  usage  types.   See  the
	      mke2fs.conf(5) manual page for  more  details.   The  filesystem
	      type-specific configuration setting found	in the [fs_types] sec-
	      tion will	override the global default found in [defaults].

	      The filesystem feature set will be further edited	 using	either
	      the  feature  set	specified by this option, or if	this option is
	      not given, by the	default_features relation for  the  filesystem
	      type being created, or in	the [defaults] section of the configu-
	      ration file.

	      The filesystem feature set is comprised of a list	 of  features,
	      separated	 by commas, that are to	be enabled.  To	disable	a fea-
	      ture, simply prefix the feature name with	a  caret ('^') charac-
	      ter.   The  pseudo-filesystem  feature  "none"  will  clear  all
	      filesystem features.

			  Use hashed b-trees to	speed up lookups in large  di-

		   extent Instead of using the indirect	block scheme for stor-
			  ing the location of data blocks in an	inode, use ex-
			  tents	instead.  This is a much more efficient	encod-
			  ing which speeds up  filesystem  access,  especially
			  for large files.

			  Store	file type information in directory entries.

			  Allow	 the per-block group metadata (allocation bit-
			  maps and inode tables) to be placed anywhere on  the
			  storage  media.   In addition, mke2fs	will place the
			  per-block group metadata together  starting  at  the
			  first	 block	group  of  each	"flex_bg group".   The
			  size of the flex_bg group can	be specified using the
			  -G option.

			  Create an ext3 journal (as if	using the -j option).

			  Create  an external ext3 journal on the given	device
			  instead of a regular ext2 filesystem.	 Note that ex-
			  ternal-journal  must	be created with	the same block
			  size as the filesystems that will be using it.

			  Filesystem can contain files that are	 greater  than
			  2GB.	(Modern	kernels	set this feature automatically
			  when a file >	2GB is created.)

			  Reserve space	so the block  group  descriptor	 table
			  may  grow in the future.  Useful for online resizing
			  using	resize2fs.  By default mke2fs will attempt  to
			  reserve enough space so that the filesystem may grow
			  to 1024 times	its initial size.  This	can be changed
			  using	the resize extended option.

			  Create  a  filesystem	 with  fewer superblock	backup
			  copies (saves	space on large filesystems).

			  Create a filesystem without initializing all of  the
			  block	 groups.   This	feature	also enables checksums
			  and highest-inode-used  statistics  in  each	block-
			  group.   This	 feature  can speed up filesystem cre-
			  ation	time noticeably	(if  lazy_itable_init  is  en-
			  abled),  and	can  also  reduce e2fsck time dramati-
			  cally.  It is	only supported by the ext4  filesystem
			  in recent Linux kernels.

       -q     Quiet execution.	Useful if mke2fs is run	in a script.

       -r revision
	      Set  the	filesystem revision for	the new	filesystem.  Note that
	      1.2 kernels only support revision	0 filesystems.	The default is
	      to create	revision 1 filesystems.

       -S     Write  superblock	and group descriptors only.  This is useful if
	      all of the superblock and	backup superblocks are corrupted,  and
	      a	 last-ditch  recovery  method is desired.  It causes mke2fs to
	      reinitialize the superblock and  group  descriptors,  while  not
	      touching	the  inode table and the block and inode bitmaps.  The
	      e2fsck program should be run immediately after  this  option  is
	      used,  and  there	is no guarantee	that any data will be salvage-
	      able.  It	is critical to specify the correct  filesystem	block-
	      size when	using this option, or there is no chance of recovery.

       -t fs-type
	      Specify  the filesystem type (i.e., ext2,	ext3, ext4, etc.) that
	      is to be created.	 If this option	is not specified, mke2fs  will
	      pick  a default either via how the command was run (for example,
	      using a name of the form mkfs.ext2, mkfs.ext3, etc.)  or	via  a
	      default  as  defined by the /etc/mke2fs.conf(5) file.   This op-
	      tion controls which filesystem  options  are  used  by  default,
	      based	on     the    fstypes	 configuration	  stanza    in

	      If the -O	option is used to explicitly add or remove  filesystem
	      options  that should be set in the newly created filesystem, the
	      resulting	filesystem may not be supported	by the	requested  fs-
	      type.   (e.g., "mke2fs -t	ext3 -O	extents	/dev/sdXX" will	create
	      a	filesystem that	is not supported by the	ext3 implementation as
	      found  in	 the Linux kernel; and "mke2fs -t ext3 -O ^has_journal
	      /dev/hdXX" will create a filesystem that does not	have a journal
	      and  hence  will not be supported	by the ext3 filesystem code in
	      the Linux	kernel.)

       -T usage-type[,...]
	      Specify how the filesystem is going to be	used, so  that	mke2fs
	      can  choose optimal filesystem parameters	for that use.  The us-
	      age types	that are supported are defined	in  the	 configuration
	      file  /etc/mke2fs.conf(5).  The user may specify one or more us-
	      age types	using a	comma separated	list.

	      If this option is	is not specified, mke2fs will  pick  a	single
	      default  usage  type  based  on the size of the filesystem to be
	      created.	If the filesystem size is less	than  or  equal	 to  3
	      megabytes,  mke2fs  will use the filesystem type floppy.	If the
	      filesystem size is greater than 3	but less than or equal to  512
	      megabytes,  mke2fs(8) will use the filesystem small.  Otherwise,
	      mke2fs(8)	will use the default filesystem	type default.

       -U UUID
	      Create the filesystem with the specified UUID.

       -v     Verbose execution.

       -V     Print the	version	number of mke2fs and exit.

       This  version  of  mke2fs   has	 been	written	  by   Theodore	  Ts'o

       mke2fs  accepts the -f option but currently ignores it because the sec-
       ond extended file system	does not support fragments yet.
       There may be other ones.	 Please, report	them to	the author.

       mke2fs  is  part	 of  the  e2fsprogs  package  and  is  available  from

       mke2fs.conf(5), badblocks(8), dumpe2fs(8), e2fsck(8), tune2fs(8)

E2fsprogs version 1.41.14	 December 2010			     MKE2FS(8)


Want to link to this manual page? Use this URL:

home | help