MKE2FS(8)                   System Manager's Manual                  MKE2FS(8)

       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 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 compati-
              bility, but is deprecated.  The following extended  options  are

                          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 allo-

                          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-

                          Create  the  filesystem at an offset from the begin-
                          ning 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 maxi-
                          mizes 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 direc-
                          tory were set by default to the UID and GID  of  the
                          user  running  the  mke2fs command.  The root_owner=
                          option allows explicitly  specifying  these  values,
                          and  avoid side-effects for users that do not expect
                          the contents of the filesystem to  change  based  on
                          the user running mke2fs.

                          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  cre-
              ate  a filesystem even if the filesystem appears to be in use or
              is mounted (a truly dangerous thing to do), this option must  be
              specified twice.

       -g blocks-per-group
              Specify  the number of blocks in a block group.  There is gener-
              ally no reason for the user to ever set this parameter,  as  the
              default  is optimal for the filesystem.  (For administrators who
              are creating filesystems on RAID arrays, it is preferable to use
              the  stride  RAID parameter as part of the -E option rather than
              manipulating the number of blocks per group.)   This  option  is
              generally used by developers who are developing test cases.

              If  the  bigalloc feature is enabled, the -g option will specify
              the number of clusters in a block group.

       -G number-of-groups
              Specify the number of block groups that will be packed  together
              to  create  a larger virtual block group (or "flex_bg group") in
              an ext4 filesystem.  This improves meta-data locality  and  per-
              formance  on  meta-data  heavy  workloads.  The number of groups
              must be a power of 2 and may only be specified  if  the  flex_bg
              filesystem feature is enabled.

       -i bytes-per-inode
              Specify  the  bytes/inode  ratio.   mke2fs  creates an inode for
              every bytes-per-inode bytes of space on the  disk.   The  larger
              the  bytes-per-inode  ratio,  the  fewer inodes will be created.
              This value generally shouldn't be smaller than the blocksize  of
              the  filesystem,  since  in  that case more inodes would be made
              than can ever be used.  Be warned that it  is  not  possible  to
              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 main-
              tain 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 nega-
              tively 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 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

              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 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

       -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.  Features with dependencies will not  be  removed  success-
              fully.   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  descrip-
              tors, 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  over-
              write  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 sepa-
              rated          by          hyphens,          like          this:
              "c1b9d5a2-f162-11cf-9ece-0020afc76f16".   The UUID parameter may
              also be one of the following:

                   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  direc-
              tive 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
              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),

E2fsprogs version 1.44.1          March 2018                         MKE2FS(8)
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