mke2fs - create an ext2/ext3/ext4 filesystem


   mke2fs  [  -c | -l filename ] [ -b block-size ] [ -d root-directory ] [
   -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 [^]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
   device 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 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.   This  can  only be specified if the
          bigalloc 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
          compatibility,  but  is  deprecated.   The  following   extended
          options are supported:

                      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

                      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

                      Create   the   filesystem  at  an  offset  from  the
                      beginning of the device or file.  This can be useful
                      when creating disk images for virtual machines.

                      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.

                      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
                      maximizes 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
                      directory 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
                      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.

                      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
                      default 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 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
          create  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
          generally 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
          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
          change  this  ratio  on  a filesystem after it is created, so be
          careful deciding the correct value  for  this  parameter.   Note
          that  resizing  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
          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.  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
          extended   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
          inode 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
          argument using the equals ('=')  sign.   The  following  journal
          options 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
                      multiple 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,
                      external-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

          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
          automatically  pass  the  correct  parameters  to  the badblocks

   -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
          options),   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]
          subsections  for  the usage types as specified by the -T option,
          further  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]
          section 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
          configuration file.

          The filesystem feature set is comprised of a list  of  features,
          separated  by  commas,  that  are  to  be enabled.  To disable a
          feature, simply prefix the  feature  name  with  a  caret  ('^')
          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 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
          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 salvageable.  Due to the wide variety of possible
          options 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
          option,  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
          overwrite 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
          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 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
          Create the filesystem with the specified 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
          directive 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
          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  accepts  the  -f  option  but  currently ignores it because the
   second extended file system does not support fragments yet.
   There may be other ones.  Please, report them to the author.


   mke2fs  is  part  of  the  e2fsprogs  package  and  is  available  from


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


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