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MKE2FS(8)							     MKE2FS(8)

NAME
       mke2fs - create an ext2/ext3/ext4 filesystem

SYNOPSIS
       mke2fs [ -c | -l filename ] [ -b block-size ] [ -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	negative, 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 cer‐
	      tain hardware devices which require that the blocksize be a mul‐
	      tiple 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.

       -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:

		   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 initial‐
			  ization.

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

       -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.

       -G number-of-groups
	      Specify  the number of block groups that will be packed together
	      to create one large virtual block group on an  ext4  filesystem.
	      This  improves  meta-data	 locality and performance 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  102,400
			  filesystem blocks.

		   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.

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

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

		   filetype
			  Store file type information in directory entries.

		   flex_bg
			  Allow bitmaps and inode tables for a block group  to
			  be placed anywhere on the storage media (use with -G
			  option to group meta-data in order to create a large
			  virtual block group).

		   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.

		   extent 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.

		   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.

		   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).

       -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(5)  file.	  This
	      option controls which filesystem options are  used  by  default,
	      based	on     the    fstypes	 configuration	  stanza    in
	      /etc/mke2fs.conf(5).

	      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 extents /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(5).   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 small.  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.

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 1.41.9	  August 2009			     MKE2FS(8)
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