Provided by: e2fsprogs_1.46.3-1ubuntu3_amd64 bug


       mke2fs - create an ext2/ext3/ext4 filesystem


       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 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  powers  of  two
              from  1024  up  to  65536  (however  note  that  the  kernel  is able to mount only
              filesystems 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  filesystem  size  and  the
              expected  usage  of  the filesystem (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

       -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:

                          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 parameter, its default  value  is  used.
                          encoding-flags  should  be  a  comma-separated  lists  of  flags  to be
                          enabled.  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  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 allocator.

                          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 written.

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

                          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.

                          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
                          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     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

       -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 number 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.

              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 inode size is 256 bytes for
              most file systems, except for small file systems where the inode size will  be  128

       -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

       -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)

                          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 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

                          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

                          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 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 automatically
              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 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

       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
              Set the universally unique identifier (UUID) of the filesystem to UUID.  The format
              of  the  UUID  is  a  series  of  hex  digits  separated  by  hyphens,  like  this:
              "c1b9d5a2-f162-11cf-9ece-0020afc76f16".  The UUID parameter may also be one of  the

                   clear  clear the filesystem 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 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 mke2fs.conf(5)).

              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 filesystem 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), ext4(5)