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

       mke2fs - create an ext2/ext3/ext4 filesystem

       mke2fs [ -c | -l filename ] [ -b block-size ] [ -C cluster-size ] [ -d
       root-directory ] [ -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 ]

       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 suffix, 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, gigabytes, terabytes, etc.  If
       fs-size is omitted, mke2fs will create the file system based on the
       device size.

       If mke2fs is run as mkfs.XXX (i.e., mkfs.ext2, mkfs.ext3, or mkfs.ext4)
       the option -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
       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.

       -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 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 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, but is deprecated.  The following extended
              options are supported:

                          Enable the casefold feature in the super block and
                          set encoding-name as the encoding to be used.  If
                          encoding-name is not specified, the encoding defined
                          in mke2fs.conf(5) is used.

                          Define parameters for file name character encoding
                          operations.  If a flag is not changed using this
                          parameter, its default value is used.  encoding-
                          flags should be a comma-separated lists of flags to
                          be enabled.  To disable a flag, add it to the list
                          with the prefix "no".

                          The only flag that can be set right now is strict
                          which means that invalid strings should be rejected
                          by the file system.  In the default configuration,
                          the strict flag is disabled.

                          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.

                          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

                          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

                          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.

                          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.

                          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 attributes.

                          If the sparse_super2 file system feature is enabled
                          this option controls whether there will be 0, 1, or
                          2 backup superblocks created in the file system.

                   packed_meta_blocks[= <0 to disable, 1 to enable>]
                          Place the allocation bitmaps and the inode table at
                          the beginning of the disk.  This option requires
                          that the flex_bg file system feature to be enabled
                          in order for it to have effect, 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.

                          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.

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

                          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.

                          Do not attempt to discard blocks at mkfs time.

                          Specify the which  quota types (usrquota, grpquota,
                          prjquota) which should be enabled in the created
                          file system.  The argument 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 option
                          is not specified is both user and group quotas.  If
                          the project feature is enabled that project quotas
                          will be initialized 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 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
              careful deciding the correct value for this parameter.  Note
              that resizing 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.

              File systems with an inode size of 128 bytes do not support
              timestamps beyond January 19, 2038.  Inodes which are 256 bytes
              or larger will support extended timestamps, project id's, and
              the ability to store some extended attributes in the inode table
              for improved performance.

              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:

                          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)

                          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.

                          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

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

       -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 badblocks

       -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

       -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.  Features with dependencies 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 kernels only support revision 0 filesystems.  The default is
              to create revision 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 desired by experienced users.  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 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
              overwrite all of the superblocks correctly, and at least some
              filesystem corruption 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 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 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 restore 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 specified via the
              E2FSPROGS_UNDO_DIR environment variable or the undo_dir
              directive in the configuration file.

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

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

              Determines the location of the configuration file (see

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

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

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

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

       This version of mke2fs has been written by Theodore Ts'o

       mke2fs is part of the e2fsprogs package and is available from

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

E2fsprogs version 1.45.6          March 2020                         MKE2FS(8)