Provided by: e2fsprogs_1.42.9-3ubuntu1.3_amd64 bug


       mke2fs - create an ext2/ext3/ext4 filesystem


       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 [^]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 ] device [ blocks-count ]

       mke2fs -O journal_dev [ -b block-size ] [ -L volume-label ] [ -n ] [ -q ] [ -v ] external-
       journal [ blocks-count ]


       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

       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

       -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     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
              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 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.

                          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  which  quota  type ('usr' or 'grp') is to be initialized. This
                          option has effect only if  the  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 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 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

       -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)

                          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  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 salvageable.  It is critical to specify the correct
              filesystem blocksize 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.


              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  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), ext4(5)