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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 ] [ -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	]

DESCRIPTION
       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
       specified.

       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     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 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.

		   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.

		   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.

       -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)

		   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  ('^')	 or  a
	      minus  ('-')  character.	Features with dependencies will	not be
	      removed successfully.  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 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 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 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 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.

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 1.42.9	 December 2013			     MKE2FS(8)

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

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