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

NAME
       mke2fs - create an ext2/ext3/ext4 filesystem

SYNOPSIS
       mke2fs  [ -c | -l filename ] [ -b block-size ] [ -C cluster-size ] [ -d root-di‐
       rectory ] [ -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 ]

DESCRIPTION
       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  suf‐
       fix, 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,  giga‐
       bytes,  terabytes, etc.  If fs-size is omitted, mke2fs will create the file sys‐
       tem based on the device size.

       If mke2fs is run as mkfs.XXX (i.e., mkfs.ext2, mkfs.ext3, or mkfs.ext4) the  op‐
       tion  -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 overrid‐
       den by the options listed below, are controlled by the /etc/mke2fs.conf configu‐
       ration 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  filesys‐
              tem  (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 clus‐
              ter.   This  can  only  be  specified if the bigalloc feature is enabled.
              (See the ext4 (5) man page for more details about  bigalloc.)    The  de‐
              fault 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 sep‐
              arated, and may take an argument using the equals ('=') sign.  The -E op‐
              tion used to be -R in earlier versions of mke2fs.  The -R option is still
              accepted for backwards compatibility, but is deprecated.   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  inter‐
                          val.   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 writ‐
                          ten to disk before moving to the next disk,  which  is  some‐
                          times  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 per‐
                          formance.  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.

                   offset=offset
                          Create the filesystem at an offset from the beginning of  the
                          device or file.  This can be useful when creating disk images
                          for virtual machines.

                   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 back‐
                          ground 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 op‐
                          tion value is omitted, it defaults to 1 to enable lazy  jour‐
                          nal inode zeroing.

                   no_copy_xattrs
                          Normally  mke2fs  will  copy  the  extended attributes of the
                          files in the directory hierarchy specified via the (optional)
                          -d  option.   This will disable the copy and leaves the files
                          in the newly created file system  without  any  extended  at‐
                          tributes.

                   num_backup_sb=<0|1|2>
                          If  the sparse_super2 file system feature is enabled this op‐
                          tion controls whether there will be 0, 1,  or  2  backup  su‐
                          perblocks created in the file system.

                   packed_meta_blocks[= <0 to disable, 1 to enable>]
                          Place  the  allocation bitmaps and the inode table at the be‐
                          ginning of the disk.  This option requires that  the  flex_bg
                          file system feature to be enabled in order for it to have ef‐
                          fect, 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
                          maximizes  the  range of contiguous data blocks, which can be
                          useful for certain specialized use cases, such  as  supported
                          Shingled Drives.

                   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 directory 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  in‐
                          ode 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 the which  quota types (usrquota, grpquota, prjquota)
                          which  should be enabled in the created file system.  The ar‐
                          gument 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  op‐
                          tion  is not specified is both user and group quotas.  If the
                          project feature is enabled that project quotas will  be  ini‐
                          tialized 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 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.

              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 performance on meta-data heavy work‐
              loads.   The number of groups must be a power of 2 and may only be speci‐
              fied 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 ra‐
              tio, the fewer inodes will be created.  This value generally shouldn't be
              smaller than the blocksize of the filesystem, since in that case more in‐
              odes would be made than can ever be used.  Be warned that it is not  pos‐
              sible  to  change  this  ratio on a filesystem after it is created, so be
              careful deciding the correct value for this parameter.  Note that  resiz‐
              ing a filesystem changes the number of inodes to maintain 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 negatively 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 im‐
              proved  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 in‐
              ode 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 ap‐
              propriately 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  filesys‐
                          tem) 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 sys‐
                          tem size (whichever is smaller)

                   location=journal-location
                          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.

                   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 sin‐
                          gle  external  journal, the Linux kernel and e2fsck(8) do not
                          currently support shared external journals yet.

                          Instead of specifying a device name directly,  external-jour‐
                          nal  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 jour‐
                          nal.  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 automatically pass the correct parameters to the bad‐
              blocks 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 pro‐
              cesses are prevented from writing to the filesystem.   The  default  per‐
              centage 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  deter‐
              mine  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), over‐
              riding the default filesystem options.  The features that are enabled  by
              default  are  specified by the base_features relation, either in the [de‐
              faults] 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] subsec‐
              tions  for the filesystem and usage types.  See the mke2fs.conf(5) manual
              page for more details.  The filesystem type-specific  configuration  set‐
              ting  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  fea‐
              ture 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.  Features with dependen‐
              cies will not be removed  successfully.   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 ker‐
              nels only support revision 0 filesystems.  The default is to create revi‐
              sion 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 de‐
              sired by experienced users.  It causes mke2fs  to  reinitialize  the  su‐
              perblock  and  group  descriptors, while not touching the inode table and
              the block and inode bitmaps.  The e2fsck program should  be  run  immedi‐
              ately  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 cor‐
              ruption  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 ei‐
              ther 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 sup‐
              ported 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 us‐
              age  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  separated  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 re‐
              store 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  speci‐
              fied  via the E2FSPROGS_UNDO_DIR environment variable or the undo_dir di‐
              rective in the configuration file.

              WARNING: The undo file cannot be used to recover from a power  or  system
              crash.

ENVIRONMENT
       MKE2FS_SYNC
              If  set to non-zero integer value, its value is used to determine how of‐
              ten 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 logical
              sector size of the device.

       MKE2FS_DEVICE_PHYS_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>.

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 1.44.5             December 2018                            MKE2FS(8)

Usage: mkfs.ext2 [-c|-l filename] [-b block-size] [-C cluster-size]
        [-i bytes-per-inode] [-I inode-size] [-J journal-options]
        [-G flex-group-size] [-N number-of-inodes] [-d root-directory]
        [-m reserved-blocks-percentage] [-o creator-os]
        [-g blocks-per-group] [-L volume-label] [-M last-mounted-directory]
        [-O feature[,...]] [-r fs-revision] [-E extended-option[,...]]
        [-t fs-type] [-T usage-type ] [-U UUID] [-e errors_behavior][-z undo_file]
        [-jnqvDFSV] device [blocks-count]