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

       mke2fs -	create an ext2/ext3/ext4 filesystem

       mke2fs  [ -c | -l filename ] [ -b block-size ] [	-C cluster-size	] [ -d
       root-directory ]	[ -D ] [ -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 ]

       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.

       -b block-size
	      Specify  the  size  of blocks in bytes.  Valid block-size	values
	      are powers of two	from 1024 up to	65536 (however note  that  the
	      kernel is	able to	mount only filesystems with block-size smaller
	      or equal to the system page size - 4k on x86 systems, up to  64k
	      on  ppc64	 or  aarch64  depending	 on kernel configuration).  If
	      omitted, block-size is heuristically determined by the  filesys-
	      tem  size	 and  the expected usage of the	filesystem (see	the -T
	      option).	In most	common cases, the default block	size is	4k. 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
	      require 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

			  Enable  the  casefold	feature	in the super block and
			  set encoding-name as the encoding to	be  used.   If
			  encoding-name	is not specified, the encoding defined
			  in mke2fs.conf(5) is used.

			  Define parameters for	file name  character  encoding
			  operations.  If a flag is not	changed	using this pa-
			  rameter, its default value is	used.	encoding-flags
			  should be a comma-separated lists of flags to	be en-
			  abled.  To disable a flag, add it to the  list  with
			  the prefix "no".

			  The  only  flag  that	can be set right now is	strict
			  which	means that invalid strings should be  rejected
			  by  the  file	system.	 In the	default	configuration,
			  the strict flag is disabled.

			  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.

			  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-

			  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.

			  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.

			  Normally mke2fs will copy the	extended attributes of
			  the  files  in the directory hierarchy specified via
			  the (optional) -d option.   This  will  disable  the
			  copy	and leaves the files in	the newly created file
			  system without any extended attributes.

			  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.

			  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.

			  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.

			  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     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 number of inodes to	maintain  this

       -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.

	      File systems with	an inode size of  128  bytes  do  not  support
	      timestamps  beyond January 19, 2038.  Inodes which are 256 bytes
	      or larger	will support extended timestamps,  project  id's,  and
	      the ability to store some	extended attributes in the inode table
	      for improved performance.

	      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:

			  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)

			  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.

			  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.   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
	      Set  the	universally unique identifier (UUID) of	the filesystem
	      to UUID.	The format of the UUID is a series of hex digits sepa-
	      rated	     by		 hyphens,	   like		 this:
	      "c1b9d5a2-f162-11cf-9ece-0020afc76f16".  The UUID	parameter  may
	      also be one of the following:

		   clear  clear	the filesystem UUID

		   random generate a new randomly-generated UUID

		   time	  generate a new time-based 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.

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

	      Determines  the  location	 of  the   configuration   file	  (see

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

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

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

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

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

       mke2fs  is  part	 of  the  e2fsprogs  package  and  is  available  from

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

E2fsprogs version 1.45.7	 January 2021			     MKE2FS(8)


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