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

       mke2fs -	create an ext2/ext3/ext4 file system

       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 file system, 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  file  system,  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	 file  systems 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  file
	      system  size  and	the expected usage of the file system (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	file systems 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 file system.

       -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 file system error	will cause e2fsck(8) to	 check
	      the  file	system on the next boot.  error-behavior can be	one of
	      the following:

		   continue    Continue	normal execution.

		   remount-ro  Remount file system read-only.

		   panic       Cause a kernel panic.

       -E extended-options
	      Set extended options for the file	system.	 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	file system  for  a  RAID  array  with
			  stride-size  file  system 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  file
			  system metadata like bitmaps at mke2fs time to avoid
			  placing them on a single disk, which can  hurt  per-
			  formance.   It may also be used by the block alloca-

			  Configure the	file system  for  a  RAID  array  with
			  stripe-width	file system 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 file system 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 file	system
			  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 file  system  initialization  notice-
			  ably,	 but it	requires the kernel to finish initial-
			  izing	the file system	in  the	 background  when  the
			  file	system	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 file system 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 file system to change  based  on
			  the user running mke2fs.

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

			  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 file
			  system 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 file system, 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  file system even if the file system 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 file system.  (For administrators who
	      are creating file	systems	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 file system.  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
	      file system 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
	      file  system,  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	file system after it is	created, so be careful
	      deciding the correct value for this parameter.  Note that	resiz-
	      ing  a file system 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	file system and	can also nega-
	      tively impact performance.  It is	not possible  to  change  this
	      value after the file system 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 file system 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
	      file  system) stored within the file system.  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
			  file	system)	 of  size journal-size megabytes.  The
			  size of the journal must be at least 1024 file  sys-
			  tem blocks (i.e., 1MB	if using 1k blocks, 4MB	if us-
			  ing 4k blocks,  etc.)	  and  may  be	no  more  than
			  10,240,000 file system blocks	or half	the total file
			  system size (whichever is smaller)

			  Create an additional fast  commit  journal  area  of
			  size	fast-commit-size  kilobytes.   This  option is
			  only valid if	fast_commit feature is enabled on  the
			  file	system.	If this	option is not specified	and if
			  fast_commit feature is turned	on, fast  commit  area
			  size	defaults  to  journal-size / 64	megabytes. The
			  total	size of	the journal with  fast_commit  feature
			  set  is  journal-size	 +  ( fast-commit-size * 1024)
			  megabytes. The total journal size  may  be  no  more
			  than 10,240,000 file system 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 file system 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 file system.  In
			  addition, while there	is support for attaching  mul-
			  tiple	file systems 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 file

       -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 file system to new-volume-label.
	      The maximum length of the	volume label is	16 bytes.

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

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

       -n     Causes  mke2fs to	not actually create a file system, but display
	      what it would do if it were to create a file system.   This  can
	      be  used to determine the	location of the	backup superblocks for
	      a	particular file	system,	so long	as the mke2fs parameters  that
	      were passed when the file	system 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 file system	(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 file	system.	 The creator field is set  by  default
	      to the name of the OS the	mke2fs executable was compiled for.

       -O [^]feature[,...]
	      Create  a	 file  system with the given features (file system op-
	      tions), overriding the default file system  options.   The  fea-
	      tures that are enabled by	default	are specified by the base_fea-
	      tures  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  file	 system	 and  usage  types.   See  the
	      mke2fs.conf(5)  manual  page  for	more details.  The file	system
	      type-specific configuration setting found	in the [fs_types] sec-
	      tion will	override the global default found in [defaults].

	      The  file	system 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 file	system
	      type being created, or in	the [defaults] section of the configu-
	      ration file.

	      The  file	system 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-file	 system	 feature "none"	will clear all
	      file system 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 file system revision for the new file system.  Note that
	      1.2  kernels  only support revision 0 file systems.  The default
	      is to create revision 1 file systems.

       -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 file	system will be	further	 corrupted.   In  some
	      cases,  such as file systems 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 file
	      system corruption	will occur.  It	is best	to run this on a  full
	      copy  of	the  file system so other options can be tried if this
	      doesn't work.

       -t fs-type
	      Specify the file system 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 file system 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 file	system
	      options that should be set in the	newly created file system, the
	      resulting	file system may	not be supported by the	requested  fs-
	      type.  (e.g., "mke2fs -t ext3 -O extent /dev/sdXX" will create a
	      file system 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 file system that	does not have a	 jour-
	      nal and hence will not be	supported by the ext3 file system code
	      in the Linux kernel.)

       -T usage-type[,...]
	      Specify how the file system is going to be used, so that	mke2fs
	      can choose optimal file system 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 file system to be
	      created.	If the file system size	 is  less  than	 3  megabytes,
	      mke2fs will use the file system type floppy.  If the file	system
	      size is greater than or equal to 3 but less than 512  megabytes,
	      mke2fs(8)	will use the file system type small.  If the file sys-
	      tem size is greater than or equal	to 4 terabytes but  less  than
	      16  terabytes,  mke2fs(8)	will use the file system type big.  If
	      the file system size is greater than or equal to	16  terabytes,
	      mke2fs(8)	 will  use  the	 file  system  type  huge.  Otherwise,
	      mke2fs(8)	will use the default file system type default.

       -U UUID
	      Set the universally unique identifier (UUID) of the file	system
	      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 file system	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 file	system 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 1.46.4	  August 2021			     MKE2FS(8)


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