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MKE2FS(8)		    System Manager's Manual		     MKE2FS(8)

NAME
       mke2fs -	create an ext2/ext3/ext4 filesystem

SYNOPSIS
       mke2fs  [  -c | -l filename ] [ -b block-size ] [ -d root-directory ] [
       -D ] [ -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 [^]feature[,...]  ] [ -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 ] [	-e errors-behavior ] [ -z undo_file ] device [ fs-size ]

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

DESCRIPTION
       mke2fs  is used to create an ext2, ext3,	or ext4	filesystem, usually in
       a disk partition	(or file) named	by device.

       The file	system size is specified by fs-size.  If fs-size does not have
       a  suffix,  it  is interpreted as power-of-two kilobytes, unless	the -b
       blocksize option	is specified, in which case fs-size is interpreted  as
       the  number  of	blocksize blocks.   If the fs-size is suffixed by 'k',
       'm', 'g', 't' (either upper-case	or lower-case),	then it	is interpreted
       in  power-of-two	 kilobytes,  megabytes,	gigabytes, terabytes, etc.  If
       fs-size is omitted, mke2fs will create the file system based on the de-
       vice size.

       If mke2fs is run	as mkfs.XXX (i.e., mkfs.ext2, mkfs.ext3, or mkfs.ext4)
       the option -t XXX is implied; so	mkfs.ext3 will create  a  file	system
       for  use	 with  ext3,  mkfs.ext4	will create a file system for use with
       ext4, and so on.

       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.

OPTIONS
       -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.

       -C  cluster-size
	      Specify  the  size of cluster in bytes for filesystems using the
	      bigalloc feature.	 Valid cluster-size values are	from  2048  to
	      256M  bytes  per cluster.	 This can only be specified if the bi-
	      galloc feature is	enabled.  (See the ext4	(5) man	page for  more
	      details  about bigalloc.)	  The default cluster size if bigalloc
	      is enabled is 16 times the block size.

       -d root-directory
	      Copy the contents	of the given directory into the	root directory
	      of the filesystem.

       -D     Use  direct  I/O	when  writing to the disk.  This avoids	mke2fs
	      dirtying a lot of	buffer cache memory, which  may	 impact	 other
	      applications  running  on	a busy server.	This option will cause
	      mke2fs to	run much more slowly, however, so there	is a  tradeoff
	      to using direct I/O.

       -e error-behavior
	      Change the behavior of the kernel	code when errors are detected.
	      In all cases, a filesystem error will cause e2fsck(8)  to	 check
	      the  filesystem  on the next boot.  error-behavior can be	one of
	      the following:

		   continue    Continue	normal execution.

		   remount-ro  Remount filesystem read-only.

		   panic       Cause a kernel panic.

       -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, but is deprecated.  The following	extended  options  are
	      supported:

		   mmp_update_interval=interval
			  Adjust  the  initial MMP update interval to interval
			  seconds.  Specifying an interval of 0	means  to  use
			  the  default	interval.  The specified interval must
			  be less than 300 seconds.   Requires	that  the  mmp
			  feature be enabled.

		   stride=stride-size
			  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-
			  cator.

		   stripe_width=stripe-width
			  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-
			  ten.

		   offset=offset
			  Create  the  filesystem at an	offset from the	begin-
			  ning of the device or	file.  This can	be useful when
			  creating disk	images for virtual machines.

		   resize=max-online-resize
			  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 zeroing.

		   lazy_journal_init[= _0 to disable, 1	to enable_]
			  If  enabled, the journal inode will not be fully ze-
			  roed out by mke2fs.  This speeds up filesystem  ini-
			  tialization  noticeably, but carries some small risk
			  if the system	crashes	before the  journal  has  been
			  overwritten  entirely	one time.  If the option value
			  is omitted, it defaults to 1 to enable lazy  journal
			  inode	zeroing.

		   num_backup_sb=_0|1|2_
			  If  the sparse_super2	file system feature is enabled
			  this option controls whether there will be 0,	1,  or
			  2 backup superblocks created in the file system.

		   packed_meta_blocks[=	_0 to disable, 1 to enable_]
			  Place	 the allocation	bitmaps	and the	inode table at
			  the beginning	of the	disk.	This  option  requires
			  that	the  flex_bg file system feature to be enabled
			  in order for it to have effect, and will also	create
			  the  journal	at  the	 beginning of the file system.
			  This option is useful	for flash devices that use SLC
			  flash	 at  the beginning of the disk.	 It also maxi-
			  mizes	the range of contiguous	data blocks, which can
			  be useful for	certain	specialized use	cases, such as
			  supported Shingled Drives.

		   root_owner[=uid:gid]
			  Specify the numeric user and group ID	 of  the  root
			  directory.  If no UID:GID is specified, use the user
			  and group ID of the user running mke2fs.  In	mke2fs
			  1.42	and earlier the	UID and	GID of the root	direc-
			  tory were set	by default to the UID and GID  of  the
			  user	running	 the  mke2fs command.  The root_owner=
			  option allows	explicitly  specifying	these  values,
			  and  avoid side-effects for users that do not	expect
			  the contents of the filesystem to  change  based  on
			  the user running mke2fs.

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

		   discard
			  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.

		   nodiscard
			  Do not attempt to discard blocks at mkfs time.

		   quotatype
			  Specify the which  quota types (usrquota,  grpquota,
			  prjquota)  which  should  be	enabled	in the created
			  file system.	The argument of	this  extended	option
			  should  be  a	colon separated	list.  This option has
			  effect only if the quota feature is set.    The  de-
			  fault	 quota	types to be initialized	if this	option
			  is not specified is both user	and group quotas.   If
			  the  project	feature	is enabled that	project	quotas
			  will be initialized as well.

       -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.

	      If  the  bigalloc	feature	is enabled, the	-g option will specify
	      the number of clusters in	a block	group.

       -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	change
	      this  ratio  on  a filesystem after it is	created, so be careful
	      deciding the correct value for this parameter.  Note that	resiz-
	      ing  a  filesystem  changes the numer of inodes to maintain this
	      ratio.

       -I inode-size
	      Specify the size of each inode in	bytes.	The  inode-size	 value
	      must be a	power of 2 larger or equal to 128.  The	larger the in-
	      ode-size the more	space the inode	table will consume,  and  this
	      reduces  the  usable  space in the filesystem and	can also nega-
	      tively impact performance.  It is	not possible  to  change  this
	      value after the filesystem is created.

	      In  kernels  after  2.6.10 and some earlier vendor kernels it is
	      possible to utilize inodes larger	than 128 bytes	to  store  ex-
	      tended attributes	for improved 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.

	      The default inode	size is	controlled by the mke2fs.conf(5) file.
	      In the mke2fs.conf file shipped with e2fsprogs, the default  in-
	      ode  size	 is  256 bytes for most	file systems, except for small
	      file systems where the inode size	will be	128 bytes.

       -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:

		   size=journal-size
			  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 10,240,000
			  filesystem blocks or half the	total file system size
			  (whichever is	smaller)

		   location=journal-location
			  Specify the location of the journal.	 The  argument
			  journal-location  can	either be specified as a block
			  number, or if	the number has a units	suffix	(e.g.,
			  'M',	'G', etc.) interpret it	as the offset from the
			  beginning of the file	system.

		   device=external-journal
			  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
	      filesystem.

       -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
	      mounted.

       -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.  Features with dependencies will not	 be  removed  success-
	      fully.   The  pseudo-filesystem  feature	"none"	will clear all
	      filesystem features.

       For more	information about the features which can be set, please	see
	      the manual page ext4(5).

       -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 an extreme
	      measure  to  be taken only in the	very unlikely case that	all of
	      the superblock and backup	superblocks are	corrupted, and a last-
	      ditch  recovery  method  is  desired  by	experienced users.  It
	      causes mke2fs to reinitialize the	superblock and group  descrip-
	      tors, 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 salvageable.  Due	to the wide variety  of	 possible  op-
	      tions  to	 mke2fs	that affect the	on-disk	layout,	it is critical
	      to specify exactly the same format options, such	as  blocksize,
	      fs-type,	feature	 flags,	and other tunables when	using this op-
	      tion, or the filesystem will  be	further	 corrupted.   In  some
	      cases,  such  as filesystems that	have been resized, or have had
	      features enabled after format time, it is	 impossible  to	 over-
	      write  all  of  the  superblocks	correctly,  and	 at least some
	      filesystem corruption will occur.	 It is best to run this	 on  a
	      full  copy  of  the  filesystem so other options can be tried if
	      this doesn't work.

       -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 file.	  This	option
	      controls	which filesystem options are used by default, based on
	      the fstypes configuration	stanza in /etc/mke2fs.conf.

	      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 extent /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.	The user may specify one or more usage
	      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	 3  megabytes,
	      mke2fs  will  use	the filesystem type floppy.  If	the filesystem
	      size is greater than or equal to 3 but less than 512  megabytes,
	      mke2fs(8)	will use the filesystem	type small.  If	the filesystem
	      size is greater than or equal to 4 terabytes but	less  than  16
	      terabytes,  mke2fs(8)  will use the filesystem type big.	If the
	      filesystem size is  greater  than	 or  equal  to	16  terabytes,
	      mke2fs(8)	  will	use  the  filesystem  type  huge.   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.

       -z undo_file
	      Before overwriting a file	system block, write the	 old  contents
	      of  the  block to	an undo	file.  This undo file can be used with
	      e2undo(8)	to restore the old contents of the file	system	should
	      something	 go  wrong.   If  the  empty  string  is passed	as the
	      undo_file	argument, the undo file	will  be  written  to  a  file
	      named  mke2fs-device.e2undo  in  the directory specified via the
	      E2FSPROGS_UNDO_DIR environment variable or the  undo_dir	direc-
	      tive in the configuration	file.

	      WARNING: The undo	file cannot be used to recover from a power or
	      system crash.

ENVIRONMENT
       MKE2FS_SYNC
	      If set to	non-zero integer value,	its value is used to determine
	      how often	sync(2)	is called during inode table initialization.

       MKE2FS_CONFIG
	      Determines   the	 location   of	the  configuration  file  (see
	      mke2fs.conf(5)).

       MKE2FS_FIRST_META_BG
	      If set to	non-zero integer value,	its value is used to determine
	      first meta block group. This is mostly for debugging purposes.

       MKE2FS_DEVICE_SECTSIZE
	      If set to	non-zero integer value,	its value is used to determine
	      physical sector size of the device.

       MKE2FS_SKIP_CHECK_MSG
	      If set, do not show the message of  filesystem  automatic	 check
	      caused by	mount count or check interval.

AUTHOR
       This   version	of   mke2fs   has   been   written  by	Theodore  Ts'o
       <tytso@mit.edu>.

BUGS
       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.

AVAILABILITY
       mke2fs  is  part	 of  the  e2fsprogs  package  and  is  available  from
       http://e2fsprogs.sourceforge.net.

SEE ALSO
       mke2fs.conf(5),	badblocks(8),  dumpe2fs(8),   e2fsck(8),   tune2fs(8),
       ext4(5)

E2fsprogs version 1.43.4	 January 2017			     MKE2FS(8)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ENVIRONMENT | AUTHOR | BUGS | AVAILABILITY | SEE ALSO

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