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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-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 ]

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 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 cre-
       ate 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.

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 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 buf-
              fer  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 compati-
              bility, but is deprecated.  The following extended options are supported:

                   encoding=encoding-name
                          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 encod-
                          ing defined in mke2fs.conf(5) is used.

                   encoding_flags=encoding-flags
                          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  en-
                          abled.  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 in-
                          valid strings should be rejected by the file system.   In  the  default
                          configuration, the strict flag is disabled.

                   mmp_update_interval=interval
                          Adjust the initial MMP update interval to interval seconds.  Specifying
                          an interval of 0 means to use the default interval.  The specified  in-
                          terval 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 bit-
                          maps 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.

                   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 ma-
                          chines.

                   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 initial-
                          ization  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  overwrit-
                          ten  entirely one time.  If the option value is omitted, it defaults to
                          1 to enable lazy journal 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 attributes.

                   num_backup_sb=<0|1|2>
                          If  the  sparse_super2  file system feature is enabled this option con-
                          trols 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.

                   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 direc-
                          tory 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  subse-
                          quent  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.

                   quotatype
                          Specify  the  which   quota  types (usrquota, grpquota, prjquota) which
                          should be enabled in the created file system.  The argument of this ex-
                          tended option should be a colon separated list.  This option has effect
                          only if the quota feature is set.   The default quota types to be  ini-
                          tialized if this option is not specified is both user and group quotas.
                          If the project feature is enabled that project quotas will be  initial-
                          ized as well.

       -F     Force  mke2fs  to create a filesystem, even if the specified device is not a parti-
              tion 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 clus-
              ters 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 neg-
              atively  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 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  op-
              tions  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)

                   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  be-
                          ginning 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 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 su-
                          perblock 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.

       -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 re-
              sult, 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 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  con-
              tinue to function correctly after non-privileged processes are prevented from writ-
              ing 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 filesys-
              tem.   The  creator  field  is set by default to the name of the OS the mke2fs exe-
              cutable 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 configu-
              ration  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 success-
              fully.  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  su-
              perblocks 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  guar-
              antee  that  any data will be salvageable.  Due to the wide variety of possible op-
              tions 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 tun-
              ables 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 af-
              ter 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 com-
              mand 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  sup-
              ported  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-de-
              vice.e2undo in the directory specified via the E2FSPROGS_UNDO_DIR environment vari-
              able or the undo_dir directive 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 often  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 AT mit.edu>.

AVAILABILITY
       mke2fs  is  part  of  the e2fsprogs package and is available from http://e2fsprogs.source-
       forge.net.

SEE ALSO
       mke2fs.conf(5), badblocks(8), dumpe2fs(8), e2fsck(8), tune2fs(8), ext4(5)

E2fsprogs version 1.45.5                   January 2020                                 MKE2FS(8)

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