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

NAME
       mke2fs - create an ext2/ext3/ext4 filesystem

SYNOPSIS
       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  fea-
       ture[,...]  ] [ -q ] [ -r fs-revision-level ] [ -E extended-options ] [
       -v ] [ -F ] [ -L volume-label ] [ -M last-mounted-directory ] [ -S ]  [
       -t fs-type ] [ -T usage-type ] [ -U UUID ] [ -V ] device [ blocks-count
       ]

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

DESCRIPTION
       mke2fs  is used to create an ext2, ext3, or ext4 filesystem, usually in
       a disk partition.  device is the  special  file  corresponding  to  the
       device  (e.g  /dev/hdXX).   blocks-count is the number of blocks on the
       device.  If omitted, mke2fs automagically figures the file system size.
       If  called  as  mkfs.ext3  a journal is created as if the -j option was
       specified.

       The defaults of the parameters for the newly created filesystem, if not
       overridden   by  the  options  listed  below,  are  controlled  by  the
       /etc/mke2fs.conf configuration file.   See  the  mke2fs.conf(5)  manual
       page for more details.

OPTIONS
       -b block-size
              Specify  the  size  of blocks in bytes.  Valid block-size values
              are 1024, 2048 and 4096 bytes per block.  If omitted, block-size
              is  heuristically  determined  by  the  filesystem  size and the
              expected usage of the filesystem (see the -T option).  If block-
              size  is 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.  By default (if bigalloc is enabled and
              no cluster size is otherwise specified using this  option),  the
              cluster size will be 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  compati-
              bility.   The following extended options are supported:

                   mmp_update_interval=interval
                          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.

                   stride=stride-size
                          Configure  the  filesystem  for  a  RAID  array with
                          stride-size filesystem blocks. This is the number of
                          blocks  read or written to disk before moving to the
                          next disk, which is sometimes  referred  to  as  the
                          chunk   size.   This  mostly  affects  placement  of
                          filesystem metadata like bitmaps at mke2fs  time  to
                          avoid  placing them on a single disk, which can hurt
                          performance.  It may also be used by the block allo-
                          cator.

                   stripe_width=stripe-width
                          Configure  the  filesystem  for  a  RAID  array with
                          stripe-width filesystem blocks per stripe.  This  is
                          typically  stride-size * N, where N is the number of
                          data-bearing disks in the  RAID  (e.g.  for  RAID  5
                          there is one parity disk, so N will be the number of
                          disks in the array minus 1).  This allows the  block
                          allocator to prevent read-modify-write of the parity
                          in a RAID stripe if possible when the data is  writ-
                          ten.

                   resize=max-online-resize
                          Reserve   enough  space  so  that  the  block  group
                          descriptor table can grow to  support  a  filesystem
                          that has max-online-resize blocks.

                   lazy_itable_init[= <0 to disable, 1 to enable>]
                          If enabled and the uninit_bg feature is enabled, the
                          inode table will not be fully initialized by mke2fs.
                          This speeds up filesystem initialization noticeably,
                          but it requires the kernel  to  finish  initializing
                          the filesystem in the background when the filesystem
                          is first mounted.  If the option value  is  omitted,
                          it defaults to 1 to enable lazy inode table 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.

                   root_owner[=uid:gid]
                          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.

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

                   discard
                          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.

                   nodiscard
                          Do not attempt to discard blocks at mkfs time.

                   quotatype
                          Specify  which  quota type ('usr' or 'grp') is to be
                          initialized. This option  has  any  effect  only  if
                          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 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
              expand the number of inodes on a filesystem after it is created,
              so be careful deciding the correct value for this parameter.

       -I inode-size
              Specify  the  size  of  each  inode  in  bytes.   mke2fs creates
              256-byte inodes by default.  In kernels after  2.6.10  and  some
              earlier  vendor  kernels it is possible to utilize inodes larger
              than 128 bytes to store extended attributes for improved perfor-
              mance.   The  inode-size  value  must  be a power of 2 larger or
              equal to 128.  The larger the  inode-size  the  more  space  the
              inode  table  will consume, and this reduces the usable space in
              the filesystem  and  can  also  negatively  impact  performance.
              Extended  attributes stored in large inodes are not visible with
              older kernels, and such filesystems will not be  mountable  with
              2.4  kernels  at  all.   It is not possible to change this value
              after the filesystem is created.

       -j     Create the filesystem with an ext3 journal.  If the -J option is
              not  specified,  the  default journal parameters will be used to
              create an appropriately sized journal (given  the  size  of  the
              filesystem) stored within the filesystem.  Note that you must be
              using a kernel which has ext3 support in order to actually  make
              use of the journal.

       -J journal-options
              Create  the ext3 journal using options specified on the command-
              line.  Journal options are comma  separated,  and  may  take  an
              argument  using  the  equals ('=')  sign.  The following journal
              options are supported:

                   size=journal-size
                          Create an internal journal (i.e., stored inside  the
                          filesystem)  of  size  journal-size  megabytes.  The
                          size of the journal must be at least 1024 filesystem
                          blocks  (i.e.,  1MB if using 1k blocks, 4MB if using
                          4k blocks, etc.)  and may be no more than 10,240,000
                          filesystem blocks or half the total file system size
                          (whichever is smaller)

                   device=external-journal
                          Attach the filesystem to the  journal  block  device
                          located  on  external-journal.  The external journal
                          must already have been created using the command

                          mke2fs -O journal_dev external-journal

                          Note that external-journal must  have  been  created
                          with  the same block size as the new filesystem.  In
                          addition, while there is support for attaching  mul-
                          tiple  filesystems to a single external journal, the
                          Linux kernel and e2fsck(8) do not currently  support
                          shared external journals yet.

                          Instead of specifying a device name directly, exter-
                          nal-journal  can  also  be   specified   by   either
                          LABEL=label  or  UUID=UUID  to  locate  the external
                          journal by either the volume label or UUID stored in
                          the  ext2  superblock  at  the start of the journal.
                          Use dumpe2fs(8) to display a journal device's volume
                          label   and   UUID.   See  also  the  -L  option  of
                          tune2fs(8).

              Only one of the size or  device  options  can  be  given  for  a
              filesystem.

       -l filename
              Read  the  bad  blocks  list from filename.  Note that the block
              numbers in the bad block list must be generated using  the  same
              block  size  as  used  by mke2fs.  As a result, the -c option to
              mke2fs is a much simpler and less error-prone method of checking
              a disk for bad blocks before formatting it, as mke2fs will auto-
              matically pass the correct parameters to the badblocks program.

       -L new-volume-label
              Set the volume label for  the  filesystem  to  new-volume-label.
              The maximum length of the volume label is 16 bytes.

       -m reserved-blocks-percentage
              Specify the percentage of the filesystem blocks reserved for the
              super-user.  This avoids fragmentation,  and  allows  root-owned
              daemons,  such  as syslogd(8), to continue to function correctly
              after non-privileged processes are prevented from writing to the
              filesystem.  The default percentage is 5%.

       -M last-mounted-directory
              Set  the  last mounted directory for the filesystem.  This might
              be useful for the sake of utilities that key  off  of  the  last
              mounted  directory  to  determine where the filesystem should be
              mounted.

       -n     Causes mke2fs to not actually create a filesystem,  but  display
              what it would do if it were to create a filesystem.  This can be
              used to determine the location of the backup superblocks  for  a
              particular  filesystem,  so  long  as the mke2fs parameters that
              were passed when the filesystem was originally created are  used
              again.  (With the -n option added, of course!)

       -N number-of-inodes
              Overrides  the  default calculation of the number of inodes that
              should be reserved for the filesystem (which  is  based  on  the
              number  of  blocks  and the bytes-per-inode ratio).  This allows
              the user to specify the number of desired inodes directly.

       -o creator-os
              Overrides the default value of the  "creator  operating  system"
              field of the filesystem.  The creator field is set by default to
              the name of the OS the mke2fs executable was compiled for.

       -O feature[,...]
              Create  a  filesystem  with  the  given   features   (filesystem
              options),  overriding  the default filesystem options.  The fea-
              tures that are enabled by default are specified by the base_fea-
              tures   relation,  either  in  the  [defaults]  section  in  the
              /etc/mke2fs.conf configuration file, or in the  [fs_types]  sub-
              sections for the usage types as specified by the -T option, fur-
              ther modified by the features relation found in  the  [fs_types]
              subsections  for  the  filesystem  and  usage  types.   See  the
              mke2fs.conf(5) manual page for  more  details.   The  filesystem
              type-specific configuration setting found in the [fs_types] sec-
              tion will override the global default found in [defaults].

              The filesystem feature set will be further edited  using  either
              the  feature  set specified by this option, or if this option is
              not given, by the default_features relation for  the  filesystem
              type being created, or in the [defaults] section of the configu-
              ration file.

              The filesystem feature set is comprised of a list  of  features,
              separated  by commas, that are to be enabled.  To disable a fea-
              ture, simply prefix the feature name with a  caret ('^') charac-
              ter.   The  pseudo-filesystem  feature  "none"  will  clear  all
              filesystem features.

                   bigalloc
                          This feature enables clustered allocation,  so  that
                          the  unit  of allocation is a power of two number of
                          blocks.  That is, each bit in the  what  had  tradi-
                          tionally  been  known as the block allocation bitmap
                          now indicates whether a cluster is in  use  or  not,
                          where a cluster is by default composed of 16 blocks.
                          This feature can decrease the time  spent  on  doing
                          block  allocation  and brings smaller fragmentation,
                          especially for large files.  The size can be  speci-
                          fied using the -C option.

                          Warning:  The bigalloc feature is still under devel-
                          opment, and may not be  fully  supported  with  your
                          kernel or may have various bugs.  Please see the web
                          page  http://ext4.wiki.kernel.org/index.php/Bigalloc
                          for details.

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

                   extents
                          Instead of using the indirect block scheme for stor-
                          ing  the  location  of  data blocks in an inode, use
                          extents instead.  This  is  a  much  more  efficient
                          encoding  which  speeds  up filesystem access, espe-
                          cially for large  files.   (Note:  both  extent  and
                          extents  are  accepted for historical/backwards com-
                          patibility reasons.)

                   filetype
                          Store file type information in directory entries.

                   flex_bg
                          Allow the per-block group metadata (allocation  bit-
                          maps  and inode tables) to be placed anywhere on the
                          storage media.  In addition, mke2fs will  place  the
                          per-block  group  metadata  together starting at the
                          first block group of  each  "flex_bg  group".    The
                          size of the flex_bg group can be specified using the
                          -G option.

                   has_journal
                          Create an ext3 journal (as if using the -j option).

                   journal_dev
                          Create an external ext3 journal on the given  device
                          instead  of  a  regular  ext2 filesystem.  Note that
                          external-journal must be created with the same block
                          size as the filesystems that will be using it.

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

                   quota  Create  quota  inodes  (inode#  3  for userquota and
                          inode# 4 for  group  quota)  and  set  them  in  the
                          superblock.   With  this feature, the quotas will be
                          enabled  automatically  when   the   filesystem   is
                          mounted.

                   resize_inode
                          Reserve  space  so  the block group descriptor table
                          may grow in the future.  Useful for online  resizing
                          using  resize2fs.  By default mke2fs will attempt to
                          reserve enough space so that the filesystem may grow
                          to 1024 times its initial size.  This can be changed
                          using the resize extended option.

                   sparse_super
                          Create a filesystem  with  fewer  superblock  backup
                          copies (saves space on large filesystems).

                   uninit_bg
                          Create  a filesystem without initializing all of the
                          block groups.  This feature also  enables  checksums
                          and  highest-inode-used  statistics  in  each block-
                          group.  This feature can speed  up  filesystem  cre-
                          ation   time   noticeably  (if  lazy_itable_init  is
                          enabled), and can also reduce e2fsck  time  dramati-
                          cally.   It is only supported by the ext4 filesystem
                          in recent Linux kernels.

       -q     Quiet execution.  Useful if mke2fs is run in a script.

       -r revision
              Set the filesystem revision for the new filesystem.   Note  that
              1.2 kernels only support revision 0 filesystems.  The default is
              to create revision 1 filesystems.

       -S     Write superblock and group descriptors only.  This is useful  if
              all  of the superblock and backup superblocks are corrupted, and
              a last-ditch recovery method is desired.  It  causes  mke2fs  to
              reinitialize  the  superblock  and  group descriptors, while not
              touching the inode table and the block and inode  bitmaps.   The
              e2fsck  program  should  be run immediately after this option is
              used, and there is no guarantee that any data will  be  salvage-
              able.   It  is critical to specify the correct filesystem block-
              size when using this option, or there is no chance of recovery.

       -t fs-type
              Specify the filesystem type (i.e., ext2, ext3, ext4, etc.)  that
              is  to be created.  If this option is not specified, mke2fs will
              pick a default either via how the command was run (for  example,
              using  a  name  of the form mkfs.ext2, mkfs.ext3, etc.) or via a
              default as defined by the /etc/mke2fs.conf 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.

ENVIRONMENT
       MKE2FS_SYNC
              If set to non-zero integer value, its value is used to determine
              how often sync(2) is called during inode table initialization.

       MKE2FS_CONFIG
              Determines   the   location   of  the  configuration  file  (see
              mke2fs.conf(5)).

       MKE2FS_FIRST_META_BG
              If set to non-zero integer value, its value is used to determine
              first meta block group. This is mostly for debugging purposes.

       MKE2FS_DEVICE_SECTSIZE
              If set to non-zero integer value, its value is used to determine
              physical sector size of the device.

       MKE2FS_SKIP_CHECK_MSG
              If set, do not show the message of  filesystem  automatic  check
              caused by mount count or check interval.

AUTHOR
       This   version   of   mke2fs   has   been   written  by  Theodore  Ts'o
       <tytso@mit.edu>.

BUGS
       mke2fs accepts the -f option but currently ignores it because the  sec-
       ond extended file system does not support fragments yet.
       There may be other ones.  Please, report them to the author.

AVAILABILITY
       mke2fs  is  part  of  the  e2fsprogs  package  and  is  available  from
       http://e2fsprogs.sourceforge.net.

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

E2fsprogs version 1.42.8           June 2013                         MKE2FS(8)

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