mke2fs


SYNOPSIS
       mke2fs [ -c | -l filename ] [ -b block-size ] [ -f fragment-size ] [ -g
       blocks-per-group ] [ -G number-of-groups ] [ -i bytes-per-inode ] [  -I
       inode-size ] [ -j ] [ -J journal-options ] [ -K ] [ -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  negative, 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 cer-
              tain hardware devices which require that the blocksize be a mul-
              tiple 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.

       -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:

                   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
                          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 initial-
                          ization.

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

       -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.

       -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
              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  102,400
                          filesystem blocks.

                   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).

              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
                          directories.

                   extent 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.

                   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.)

                   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

              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(5)  file.    This
              option  controls  which  filesystem options are used by default,
              based    on    the    fstypes    configuration     stanza     in
              /etc/mke2fs.conf(5).

              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 extents /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(5).  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 small.   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.

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

BUGS

E2fsprogs version 1.41.11         March 2010                         MKE2FS(8)
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