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MKE2FS(8)							     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
       device  (e.g  /dev/hdXX).   blocks-count is the number of blocks on the
       device.	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
	      expected 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
	      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.	By default (if bigalloc is enabled and
	      no cluster size is otherwise specified using this	 option),  the
	      cluster size will be 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.	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
			  descriptor 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
			  zeroed out by mke2fs.	  This	speeds	up  filesystem
			  initialization  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
			  device 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  which  quota type ('usr' or 'grp') is to be
			  initialized. This option  has	 any  effect  only  if
			  quota	 feature is set. Without this extended option,
			  the default behavior is to initialize both user  and
			  group quotas.

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

       -F     Force  mke2fs  to	 create	 a  filesystem,	 even if the specified
	      device 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
	      every  bytes-per-inode  bytes  of space on the disk.  The larger
	      the bytes-per-inode ratio, the fewer  inodes  will  be  created.
	      This  value generally shouldn't be smaller than the blocksize of
	      the filesystem, since in that case more  inodes  would  be  made
	      than  can	 ever  be  used.  Be warned that it is not possible to
	      expand the number of inodes on a filesystem after it is created,
	      so be careful deciding the correct value for this parameter.

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

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

       -J journal-options
	      Create  the ext3 journal using options specified on the command-
	      line.  Journal options are comma	separated,  and	 may  take  an
	      argument	using  the  equals ('=')  sign.	 The following journal
	      options 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
			  LABEL=label  or  UUID=UUID  to  locate  the external
			  journal 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
			  label	  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
	      options),	 overriding  the default filesystem 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  filesystem	 and  usage  types.   See  the
	      mke2fs.conf(5) manual page for  more  details.   The  filesystem
	      type-specific configuration setting found in the [fs_types] sec‐
	      tion will override the global default found in [defaults].

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

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

		   bigalloc
			  This feature enables clustered allocation,  so  that
			  the  unit  of allocation is a power of two number of
			  blocks.  That is, each bit in the  what  had	tradi‐
			  tionally  been  known as the block allocation bitmap
			  now indicates whether a cluster is in	 use  or  not,
			  where a cluster is by default composed of 16 blocks.
			  This feature can decrease the time  spent  on	 doing
			  block	 allocation  and brings smaller fragmentation,
			  especially for large files.  The size can be	speci‐
			  fied using the -C option.

			  Warning:  The bigalloc feature is still under devel‐
			  opment, and may not be  fully	 supported  with  your
			  kernel or may have various bugs.  Please see the web
			  page	http://ext4.wiki.kernel.org/index.php/Bigalloc
			  for details.

		   dir_index
			  Use  hashed  b-trees	to  speed  up lookups in large
			  directories.

		   extents
			  Instead of using the indirect block scheme for stor‐
			  ing  the  location  of  data blocks in an inode, use
			  extents instead.  This  is  a	 much  more  efficient
			  encoding  which  speeds  up filesystem access, espe‐
			  cially for large  files.   (Note:  both  extent  and
			  extents  are	accepted for historical/backwards com‐
			  patibility reasons.)

		   filetype
			  Store file type information in directory entries.

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

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

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

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

		   quota  Create  quota	 inodes	 (inode#  3  for userquota and
			  inode# 4 for	group  quota)  and  set	 them  in  the
			  superblock.	With  this feature, the quotas will be
			  enabled  automatically  when	 the   filesystem   is
			  mounted.

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

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

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

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

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

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

       -t fs-type
	      Specify the filesystem type (i.e., ext2, ext3, ext4, etc.)  that
	      is  to be created.  If this option is not specified, mke2fs will
	      pick a default either via how the command was run (for  example,
	      using  a	name  of the form mkfs.ext2, mkfs.ext3, etc.) or via a
	      default as defined by the /etc/mke2fs.conf 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
	      usage 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)

E2fsprogs version 1.42.8	   June 2013			     MKE2FS(8)
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