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MKE2FS(8)                                                            MKE2FS(8)



NAME
       mke2fs - create an ext2/ext3/ext4 filesystem

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 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 ]

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 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.

       -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.   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 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.

                   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 written.

                   resize=max-online-resize
                          Reserve enough space so that the block group descriptor table can grow to support a filesys-
                          tem 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 initial-
                          ized 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
                          initialization.

                   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 initial-
                          ization. This is set as default.

                   nodiscard
                          Do not attempt to discard blocks at mkfs time.

       -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 twice.

       -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.

       -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 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 performance.  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 sepa-
              rated, and may take an argument using the equals ('=')  sign.  The following journal  options  are  sup-
              ported:

                   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  multiple  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, 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 tune2fs(8).

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

       -K     Keep,  do  not  attempt  to  discard blocks at mkfs time (discarding blocks initially is useful on solid
              state devices and sparse / thin-provisioned storage).

       -l filename
              Read the bad blocks list from filename.  Note that the block numbers in the bad block list must be  gen-
              erated using the same block size as used by mke2fs.  As a result, the -c option to mke2fs is a much sim-
              pler 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-privi-
              leged 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.   The
              pseudo-filesystem feature "none" will clear all filesystem features.

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

                   extent Instead  of  using  the  indirect block scheme for storing the location of data blocks in an
                          inode, use extents instead.  This is a much more efficient encoding which speeds up filesys-
                          tem access, especially for large files.

                   filetype
                          Store file type information in directory entries.

                   flex_bg
                          Allow  the  per-block group metadata (allocation bitmaps and inode tables) to be placed any-
                          where 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 blockgroup.  This feature can  speed  up
                          filesystem  creation  time  noticeably (if lazy_itable_init is enabled), and can also reduce
                          e2fsck time dramatically.  It is only supported by the ext4 filesystem in recent Linux  ker-
                          nels.

       -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 reinitial-
              ize 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 guar-
              antee 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(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 imple-
              mentation 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 filesys-
              tem 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 <tytsoATmit.edu>.

BUGS
       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.

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 1.41.12          May 2010                          MKE2FS(8)