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mke2fs


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.   This  can  only be specified if the
              bigalloc feature is enabled.  (See the ext4  (5)  man  page  for
              more  details  about  bigalloc.)    The  default cluster size if
              bigalloc is enabled is 16 times the block size.

       -D     Use direct I/O when writing to the  disk.   This  avoids  mke2fs
              dirtying  a  lot  of buffer cache memory, which may impact other
                          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

                   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.

       -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
              change this ratio on a filesystem after it  is  created,  so  be
              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:

                   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

       -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-

       -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.
              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),
       ext4(5)


E2fsprogs version 1.42.9 December 2013 MKE2FS(8)



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