Provided by: e2fsprogs_1.47.0-2.4~exp1ubuntu4.1_amd64 bug

NAME

       ext2 - the second extended file system
       ext3 - the third extended file system
       ext4 - the fourth extended file system

DESCRIPTION

       The  second, third, and fourth extended file systems, or ext2, ext3, and ext4 as they are commonly known,
       are Linux file systems that have historically been the default file system for many Linux  distributions.
       They  are  general  purpose  file  systems  that  have  been  designed  for  extensibility  and backwards
       compatibility.  In particular, file systems previously intended for use  with  the  ext2  and  ext3  file
       systems  can be mounted using the ext4 file system driver, and indeed in many modern Linux distributions,
       the ext4 file system driver has been configured to handle mount requests for ext2 and ext3 file systems.

FILE SYSTEM FEATURES

       A file system formatted for ext2, ext3, or ext4 can have some collection of  the  following  file  system
       feature  flags  enabled.   Some  of  these features are not supported by all implementations of the ext2,
       ext3, and ext4 file system drivers, depending on  Linux  kernel  version  in  use.   On  other  operating
       systems,  such  as  the  GNU/HURD  or FreeBSD, only a very restrictive set of file system features may be
       supported in their implementations of ext2.

       64bit
              Enables the file system to be larger than 2^32 blocks.  This  feature  is  set  automatically,  as
              needed,  but  it can be useful to specify this feature explicitly if the file system might need to
              be resized larger than 2^32 blocks, even if it  was  smaller  than  that  threshold  when  it  was
              originally created.  Note that some older kernels and older versions of e2fsprogs will not support
              file systems with this ext4 feature enabled.

       bigalloc
              This ext4 feature enables clustered block allocation, so that the unit of allocation is a power of
              two  number  of  blocks.   That is, each bit in the what had traditionally been known as the block
              allocation bitmap now indicates whether a cluster is in use or not, where a cluster is by  default
              composed  of  16  blocks.   This feature can decrease the time spent on doing block allocation and
              brings smaller fragmentation, especially for large files.  The size can  be  specified  using  the
              mke2fs -C option.

              Warning: The bigalloc feature is still under development, and may not be fully supported with your
              kernel      or     may     have     various     bugs.      Please     see     the     web     page
              http://ext4.wiki.kernel.org/index.php/Bigalloc for details.  May  clash  with  delayed  allocation
              (see nodelalloc mount option).

              This feature requires that the extent feature be enabled.

       casefold
              This  ext4  feature provides file system level character encoding support for directories with the
              casefold (+F) flag  enabled.   This  feature  is  name-preserving  on  the  disk,  but  it  allows
              applications  to  lookup for a file in the file system using an encoding equivalent version of the
              file name.

       dir_index
              Use hashed b-trees to speed up name lookups in large directories.  This feature  is  supported  by
              ext3 and ext4 file systems, and is ignored by ext2 file systems.

       dir_nlink
              Normally,  ext4  allows  an inode to have no more than 65,000 hard links.  This applies to regular
              files as well as directories, which means that there can be no more than 64,998 subdirectories  in
              a  directory  (because  each  of  the '.' and '..' entries, as well as the directory entry for the
              directory in its parent directory counts as a hard  link).   This  feature  lifts  this  limit  by
              causing  ext4 to use a link count of 1 to indicate that the number of hard links to a directory is
              not known when the link count might exceed the maximum count limit.

       ea_inode
              Normally, a file's extended attributes and associated metadata must fit within the  inode  or  the
              inode's  associated  extended  attribute  block.  This  feature  allows the value of each extended
              attribute to be placed in the data blocks of a separate inode if necessary, increasing  the  limit
              on the size and number of extended attributes per file.

       encrypt
              Enables  support  for  file-system  level  encryption  of  data  blocks and file names.  The inode
              metadata (timestamps, file size, user/group ownership, etc.) is not encrypted.

              This feature is most useful on file systems with multiple users, or where not all files should  be
              encrypted.   In  many use cases, especially on single-user systems, encryption at the block device
              layer using dm-crypt may provide much better security.

       ext_attr
              This feature enables the use of extended attributes.  This feature is supported by ext2, ext3, and
              ext4.

       extent
              This ext4 feature allows the mapping of logical block numbers for a particular inode  to  physical
              blocks  on  the  storage  device to be stored using an extent tree, which is a more efficient data
              structure than the traditional indirect block scheme used by the ext2 and ext3 file systems.   The
              use  of  the  extent tree decreases metadata block overhead, improves file system performance, and
              decreases the needed to run e2fsck(8) on the file system.  (Note:  both  extent  and  extents  are
              accepted as valid names for this feature for historical/backwards compatibility reasons.)

       extra_isize
              This  ext4 feature reserves a specific amount of space in each inode for extended metadata such as
              nanosecond timestamps and file creation time, even if the current kernel does not  currently  need
              to reserve this much space.  Without this feature, the kernel will reserve the amount of space for
              features it currently needs, and the rest may be consumed by extended attributes.

              For this feature to be useful the inode size must be 256 bytes in size or larger.

       filetype
              This  feature  enables the storage of file type information in directory entries.  This feature is
              supported by ext2, ext3, and ext4.

       flex_bg
              This ext4 feature allows the per-block group metadata (allocation bitmaps and inode tables) to  be
              placed anywhere on the storage media.  In addition, mke2fs will place the per-block group metadata
              together  starting  at  the  first  block group of each "flex_bg group".   The size of the flex_bg
              group can be specified using the -G option.

       has_journal
              Create a journal to ensure file system consistency even across  unclean  shutdowns.   Setting  the
              file  system feature is equivalent to using the -j option with mke2fs or tune2fs.  This feature is
              supported by ext3 and ext4, and ignored by the ext2 file system driver.

       huge_file
              This ext4 feature allows files to be larger than 2 terabytes in size.

       inline_data
              Allow data to be stored in the inode and extended attribute area.

       journal_dev
              This feature is enabled on the superblock found on an external journal device.  The block size for
              the external journal must be the same as the file system which uses it.

              The external journal device can be used by a file system by specifying  the  -J  device=<external-
              device> option to mke2fs(8) or tune2fs(8).

       large_dir
              This  feature increases the limit on the number of files per directory by raising the maximum size
              of directories and, for hashed b-tree directories (see  dir_index),  the  maximum  height  of  the
              hashed b-tree used to store the directory entries.

       large_file
              This  feature  flag  is set automatically by modern kernels when a file larger than 2 gigabytes is
              created.  Very old kernels could not handle large files, so this feature flag was used to prohibit
              those kernels from mounting file systems that they could not understand.

       metadata_csum
              This ext4 feature enables metadata checksumming.  This feature stores checksums  for  all  of  the
              file  system  metadata (superblock, group descriptor blocks, inode and block bitmaps, directories,
              and extent tree blocks).  The checksum algorithm used for the metadata blocks  is  different  than
              the  one  used  for  group  descriptors  with  the  uninit_bg  feature.   These  two  features are
              incompatible and metadata_csum will be used preferentially instead of uninit_bg.

       metadata_csum_seed
              This feature allows the file system to store the metadata checksum seed in the  superblock,  which
              allows the administrator to change the UUID of a file system using the metadata_csum feature while
              it is mounted.

       meta_bg
              This  ext4 feature allows file systems to be resized on-line without explicitly needing to reserve
              space for growth in the size of the block group descriptors.  This scheme is also used  to  resize
              file  systems  which  are larger than 2^32 blocks.  It is not recommended that this feature be set
              when a file system is created, since this alternate method of storing the block group  descriptors
              will  slow  down the time needed to mount the file system, and newer kernels can automatically set
              this feature as necessary when doing an online resize and no more reserved space is  available  in
              the resize inode.

       mmp
              This  ext4 feature provides multiple mount protection (MMP).  MMP helps to protect the file system
              from being multiply mounted and is useful in shared storage environments.

       project
              This ext4 feature provides project quota support. With this feature, the project ID of inode  will
              be managed when the file system is mounted.

       quota
              Create  quota  inodes  (inode  #3  for userquota and inode #4 for group quota) and set them in the
              superblock.  With this feature, the quotas will be enabled automatically when the file  system  is
              mounted.

              Causes  the quota files (i.e., user.quota and group.quota which existed in the older quota design)
              to be hidden inodes.

       resize_inode
              This file system feature indicates that space has been reserved so that the block group descriptor
              table can be extended while resizing a mounted  file  system.   The  online  resize  operation  is
              carried  out  by the kernel, triggered by resize2fs(8).  By default mke2fs will attempt to reserve
              enough space so that the file system may grow to 1024 times its initial size.  This can be changed
              using the resize extended option.

              This feature requires that the sparse_super or sparse_super2 feature be enabled.

       sparse_super
              This file system feature is set on all modern ext2, ext3, and ext4  file  systems.   It  indicates
              that  backup  copies of the superblock and block group descriptors are present only in a few block
              groups, not all of them.

       sparse_super2
              This feature indicates that there will only be at most two  backup  superblocks  and  block  group
              descriptors.  The block groups used to store the backup superblock(s) and blockgroup descriptor(s)
              are  stored  in the superblock, but typically, one will be located at the beginning of block group
              #1, and one in the last block group in the file  system.   This  feature  is  essentially  a  more
              extreme  version  of sparse_super and is designed to allow a much larger percentage of the disk to
              have contiguous blocks available for data files.

       stable_inodes
              Marks the file system's inode numbers and UUID as stable.  resize2fs(8) will not allow shrinking a
              file system with this feature, nor will tune2fs(8) allow changing its UUID.  This  feature  allows
              the use of specialized encryption settings that make use of the inode numbers and UUID.  Note that
              the encrypt feature still needs to be enabled separately.  stable_inodes is a "compat" feature, so
              old kernels will allow it.

       uninit_bg
              This  ext4  file system feature indicates that the block group descriptors will be protected using
              checksums, making it safe for mke2fs(8) to create a file system without initializing  all  of  the
              block groups.  The kernel will keep a high watermark of unused inodes, and initialize inode tables
              and  blocks lazily.  This feature speeds up the time to check the file system using e2fsck(8), and
              it also speeds up the time required for mke2fs(8) to create the file system.

       verity
              Enables support for verity protected  files.   Verity  files  are  readonly,  and  their  data  is
              transparently  verified  against  a Merkle tree hidden past the end of the file.  Using the Merkle
              tree's root hash, a verity file can be efficiently authenticated, independent of the file's size.

              This feature is most useful for  authenticating  important  read-only  files  on  read-write  file
              systems.   If the file system itself is read-only, then using dm-verity to authenticate the entire
              block device may provide much better security.

MOUNT OPTIONS

       This section describes mount options which are specific to ext2, ext3, and  ext4.   Other  generic  mount
       options may be used as well; see mount(8) for details.

Mount options for ext2

       The `ext2' file system is the standard Linux file system.  Since Linux 2.5.46, for most mount options the
       default is determined by the file system superblock. Set them with tune2fs(8).

       acl|noacl
              Support POSIX Access Control Lists (or not).  See the acl(5) manual page.

       bsddf|minixdf
              Set  the  behavior  for  the statfs system call. The minixdf behavior is to return in the f_blocks
              field the total number of blocks of the file system,  while  the  bsddf  behavior  (which  is  the
              default)  is  to  subtract  the overhead blocks used by the ext2 file system and not available for
              file storage. Thus

              % mount /k -o minixdf; df /k; umount /k
              File System  1024-blocks   Used  Available  Capacity  Mounted on
              /dev/sda6      2630655    86954   2412169      3%     /k

              % mount /k -o bsddf; df /k; umount /k
              File System  1024-blocks  Used  Available  Capacity  Mounted on
              /dev/sda6      2543714      13   2412169      0%     /k

              (Note that this example shows that one can add command  line  options  to  the  options  given  in
              /etc/fstab.)

       check=none or nocheck
              No  checking  is  done  at  mount  time.  This is the default. This is fast.  It is wise to invoke
              e2fsck(8) every now and  then,  e.g.  at  boot  time.  The  non-default  behavior  is  unsupported
              (check=normal  and  check=strict  options  have been removed). Note that these mount options don't
              have to be supported if ext4 kernel driver is used for ext2 and ext3 file systems.

       debug  Print debugging info upon each (re)mount.

       errors={continue|remount-ro|panic}
              Define the behavior when an error is encountered.  (Either ignore errors and just  mark  the  file
              system  erroneous  and  continue,  or  remount  the  file  system read-only, or panic and halt the
              system.)  The default is set in the file system superblock, and can be changed using tune2fs(8).

       grpid|bsdgroups and nogrpid|sysvgroups
              These options define what group id a newly created file gets.  When grpid is  set,  it  takes  the
              group  id  of  the directory in which it is created; otherwise (the default) it takes the fsgid of
              the current process, unless the directory has the setgid bit set, in which case it takes  the  gid
              from the parent directory, and also gets the setgid bit set if it is a directory itself.

       grpquota|noquota|quota|usrquota
              The  usrquota (same as quota) mount option enables user quota support on the file system. grpquota
              enables group quotas support. You need the quota utilities to actually enable and manage the quota
              system.

       nouid32
              Disables 32-bit UIDs and GIDs.  This is for interoperability with older kernels which  only  store
              and expect 16-bit values.

       oldalloc or orlov
              Use old allocator or Orlov allocator for new inodes. Orlov is default.

       resgid=n and resuid=n
              The  ext2  file  system  reserves  a certain percentage of the available space (by default 5%, see
              mke2fs(8) and tune2fs(8)).  These options determine who can use the  reserved  blocks.   (Roughly:
              whoever has the specified uid, or belongs to the specified group.)

       sb=n   Instead of using the normal superblock, use an alternative superblock specified by n.  This option
              is  normally  used  when  the  primary  superblock  has  been  corrupted.   The location of backup
              superblocks is dependent on the file system's blocksize, the  number  of  blocks  per  group,  and
              features such as sparse_super.

              Additional backup superblocks can be determined by using the mke2fs program using the -n option to
              print  out  where  the  superblocks  exist,  supposing  mke2fs is supplied with arguments that are
              consistent with the file system's layout (e.g. blocksize, blocks per group, sparse_super, etc.).

              The block number here uses 1 k units. Thus, if you want to use  logical  block  32768  on  a  file
              system with 4 k blocks, use "sb=131072".

       user_xattr|nouser_xattr
              Support "user." extended attributes (or not).

Mount options for ext3

       The  ext3  file  system is a version of the ext2 file system which has been enhanced with journaling.  It
       supports the same options as ext2 as well as the following additions:

       journal_dev=devnum/journal_path=path
              When the external journal device's major/minor numbers have changed, these options allow the  user
              to  specify  the  new  journal  location.  The journal device is identified either through its new
              major/minor numbers encoded in devnum, or via a path to the device.

       norecovery/noload
              Don't load the journal on mounting.  Note that if the  file  system  was  not  unmounted  cleanly,
              skipping  the journal replay will lead to the file system containing inconsistencies that can lead
              to any number of problems.

       data={journal|ordered|writeback}
              Specifies the journaling mode for file data.  Metadata is always journaled.  To  use  modes  other
              than  ordered  on  the  root  file  system,  pass  the  mode to the kernel as boot parameter, e.g.
              rootflags=data=journal.

              journal
                     All data is committed into the journal prior to being written into the main file system.

              ordered
                     This is the default mode.  All data is forced directly out to the main file system prior to
                     its metadata being committed to the journal.

              writeback
                     Data ordering is not preserved – data may be written into the main file  system  after  its
                     metadata  has been committed to the journal.  This is rumoured to be the highest-throughput
                     option.  It guarantees internal file system integrity, however it can  allow  old  data  to
                     appear in files after a crash and journal recovery.

       data_err=ignore
              Just print an error message if an error occurs in a file data buffer in ordered mode.

       data_err=abort
              Abort the journal if an error occurs in a file data buffer in ordered mode.

       barrier=0 / barrier=1
              This  disables / enables the use of write barriers in the jbd code.  barrier=0 disables, barrier=1
              enables (default). This also requires an IO stack which can support barriers, and if jbd  gets  an
              error  on  a barrier write, it will disable barriers again with a warning.  Write barriers enforce
              proper on-disk ordering of journal commits, making volatile disk write caches safe to use, at some
              performance penalty.  If your disks are battery-backed in one way or another,  disabling  barriers
              may safely improve performance.

       commit=nrsec
              Start a journal commit every nrsec seconds.  The default value is 5 seconds.  Zero means default.

       user_xattr
              Enable Extended User Attributes. See the attr(5) manual page.

       jqfmt={vfsold|vfsv0|vfsv1}
              Apart  from the old quota system (as in ext2, jqfmt=vfsold aka version 1 quota) ext3 also supports
              journaled quotas (version 2 quota). jqfmt=vfsv0 or jqfmt=vfsv1 enables journaled quotas. Journaled
              quotas have the advantage that even after a crash no quota check is required. When the quota  file
              system  feature  is  enabled,  journaled  quotas  are used automatically, and this mount option is
              ignored.

       usrjquota=aquota.user|grpjquota=aquota.group
              For journaled quotas (jqfmt=vfsv0 or jqfmt=vfsv1), the  mount  options  usrjquota=aquota.user  and
              grpjquota=aquota.group  are  required  to tell the quota system which quota database files to use.
              When the quota file system feature is enabled, journaled quotas are used automatically,  and  this
              mount option is ignored.

Mount options for ext4

       The  ext4  file  system  is  an advanced level of the ext3 file system which incorporates scalability and
       reliability enhancements for supporting large file system.

       The options journal_dev, journal_path, norecovery, noload, data, commit, orlov, oldalloc, [no]user_xattr,
       [no]acl, bsddf, minixdf, debug, errors, data_err, grpid, bsdgroups, nogrpid, sysvgroups, resgid,  resuid,
       sb,  quota,  noquota,  nouid32,  grpquota,  usrquota,  usrjquota,  grpjquota,  and  jqfmt  are backwardly
       compatible with ext3 or ext2.

       journal_checksum | nojournal_checksum
              The journal_checksum option enables checksumming of the journal transactions.  This will allow the
              recovery code in e2fsck and the kernel to detect corruption in the  kernel.  It  is  a  compatible
              change and will be ignored by older kernels.

       journal_async_commit
              Commit  block  can  be  written  to  disk  without waiting for descriptor blocks. If enabled older
              kernels cannot mount the device.  This will enable 'journal_checksum' internally.

       barrier=0 / barrier=1 / barrier / nobarrier
              These mount options have the same effect as in ext3.  The mount options "barrier" and  "nobarrier"
              are added for consistency with other ext4 mount options.

              The ext4 file system enables write barriers by default.

       inode_readahead_blks=n
              This  tuning  parameter  controls the maximum number of inode table blocks that ext4's inode table
              readahead algorithm will pre-read into the buffer cache.  The value must be  a  power  of  2.  The
              default value is 32 blocks.

       stripe=n
              Number  of  file system blocks that mballoc will try to use for allocation size and alignment. For
              RAID5/6 systems this should be the number of data disks * RAID chunk size in file system blocks.

       delalloc
              Deferring block allocation until write-out time.

       nodelalloc
              Disable delayed allocation. Blocks are allocated when data is copied from user to page cache.

       max_batch_time=usec
              Maximum amount of time ext4 should wait for additional file system operations to be batch together
              with a synchronous write operation. Since a synchronous write operation is going to force a commit
              and then a wait for the I/O complete, it doesn't cost much, and can be a huge throughput  win,  we
              wait  for a small amount of time to see if any other transactions can piggyback on the synchronous
              write. The algorithm used is designed to  automatically  tune  for  the  speed  of  the  disk,  by
              measuring  the  amount of time (on average) that it takes to finish committing a transaction. Call
              this time the "commit time".  If the time that the transaction has been running is less  than  the
              commit  time,  ext4 will try sleeping for the commit time to see if other operations will join the
              transaction. The commit time is capped by the max_batch_time, which defaults to 15000 µs  (15 ms).
              This optimization can be turned off entirely by setting max_batch_time to 0.

       min_batch_time=usec
              This  parameter  sets  the  commit  time  (as  described  above) to be at least min_batch_time. It
              defaults to zero microseconds. Increasing this parameter may  improve  the  throughput  of  multi-
              threaded, synchronous workloads on very fast disks, at the cost of increasing latency.

       journal_ioprio=prio
              The  I/O  priority  (from  0  to  7, where 0 is the highest priority) which should be used for I/O
              operations submitted by kjournald2 during a commit operation.  This defaults  to  3,  which  is  a
              slightly higher priority than the default I/O priority.

       abort  Simulate  the effects of calling ext4_abort() for debugging purposes.  This is normally used while
              remounting a file system which is already mounted.

       auto_da_alloc|noauto_da_alloc
              Many broken applications don't use fsync() when replacing existing files via patterns such as

              fd = open("foo.new")/write(fd,...)/close(fd)/ rename("foo.new", "foo")

              or worse yet

              fd = open("foo", O_TRUNC)/write(fd,...)/close(fd).

              If auto_da_alloc is enabled, ext4 will  detect  the  replace-via-rename  and  replace-via-truncate
              patterns  and force that any delayed allocation blocks are allocated such that at the next journal
              commit, in the default data=ordered mode, the data blocks of the  new  file  are  forced  to  disk
              before the rename() operation is committed.  This provides roughly the same level of guarantees as
              ext3,  and  avoids  the  "zero-length"  problem  that  can happen when a system crashes before the
              delayed allocation blocks are forced to disk.

       noinit_itable
              Do not initialize any uninitialized inode table blocks in the background. This feature may be used
              by installation CD's so that the install process can complete as quickly as  possible;  the  inode
              table  initialization  process  would  then  be  deferred  until  the next time the file system is
              mounted.

       init_itable=n
              The lazy itable init code will wait n times the number of milliseconds it took  to  zero  out  the
              previous block group's inode table. This minimizes the impact on system performance while the file
              system's inode table is being initialized.

       discard/nodiscard
              Controls  whether  ext4  should  issue  discard/TRIM  commands to the underlying block device when
              blocks are freed.  This is useful for SSD devices and sparse/thinly-provisioned LUNs,  but  it  is
              off by default until sufficient testing has been done.

       block_validity/noblock_validity
              This  option  enables/disables  the  in-kernel  facility  for tracking file system metadata blocks
              within internal data structures. This allows multi-block allocator and other routines  to  quickly
              locate  extents  which might overlap with file system metadata blocks. This option is intended for
              debugging purposes and since it negatively affects the performance, it is off by default.

       dioread_lock/dioread_nolock
              Controls whether or not ext4 should use the DIO read locking.  If  the  dioread_nolock  option  is
              specified  ext4  will  allocate uninitialized extent before buffer write and convert the extent to
              initialized after IO completes.  This approach allows ext4 code to avoid using inode mutex,  which
              improves  scalability  on high speed storages. However this does not work with data journaling and
              dioread_nolock option will be ignored with kernel warning.  Note that dioread_nolock code path  is
              only used for extent-based files.  Because of the restrictions this options comprises it is off by
              default (e.g. dioread_lock).

       max_dir_size_kb=n
              This  limits  the  size of the directories so that any attempt to expand them beyond the specified
              limit in kilobytes will cause an ENOSPC error. This is useful in memory-constrained  environments,
              where  a  very  large  directory  can cause severe performance problems or even provoke the Out Of
              Memory killer. (For example, if there is only 512 MB memory  available,  a  176 MB  directory  may
              seriously cramp the system's style.)

       i_version
              Enable 64-bit inode version support. This option is off by default.

       nombcache
              This  option  disables  use  of  mbcache  for  extended  attribute deduplication. On systems where
              extended attributes are rarely or never shared between files, use  of  mbcache  for  deduplication
              adds unnecessary computational overhead.

       prjquota
              The  prjquota  mount  option enables project quota support on the file system.  You need the quota
              utilities to actually enable and manage the quota system.  This mount option requires the  project
              file system feature.

FILE ATTRIBUTES

       The  ext2,  ext3,  and  ext4  file systems support setting the following file attributes on Linux systems
       using the chattr(1) utility:

       a - append only

       A - no atime updates

       d - no dump

       D - synchronous directory updates

       i - immutable

       S - synchronous updates

       u - undeletable

       In addition, the ext3 and ext4 file systems support the following flag:

       j - data journaling

       Finally, the ext4 file system also supports the following flag:

       e - extents format

       For descriptions of these attribute flags, please refer to the chattr(1) man page.

KERNEL SUPPORT

       This section lists the file system driver (e.g., ext2, ext3, ext4) and upstream kernel  version  where  a
       particular file system feature was supported.  Note that in some cases the feature was present in earlier
       kernel  versions, but there were known, serious bugs.  In other cases the feature may still be considered
       in an experimental state.  Finally, note that some distributions may have backported features into  older
       kernels;  in  particular  the  kernel  versions  in  certain  "enterprise distributions" can be extremely
       misleading.

       filetype            ext2, 2.2.0

       sparse_super        ext2, 2.2.0

       large_file          ext2, 2.2.0

       has_journal         ext3, 2.4.15

       ext_attr            ext2/ext3, 2.6.0

       dir_index           ext3, 2.6.0

       resize_inode        ext3, 2.6.10 (online resizing)

       64bit               ext4, 2.6.28

       dir_nlink           ext4, 2.6.28

       extent              ext4, 2.6.28

       extra_isize         ext4, 2.6.28

       flex_bg             ext4, 2.6.28

       huge_file           ext4, 2.6.28

       meta_bg             ext4, 2.6.28

       uninit_bg           ext4, 2.6.28

       mmp                 ext4, 3.0

       bigalloc            ext4, 3.2

       quota               ext4, 3.6

       inline_data         ext4, 3.8

       sparse_super2       ext4, 3.16

       metadata_csum       ext4, 3.18

       encrypt             ext4, 4.1

       metadata_csum_seed  ext4, 4.4

       project             ext4, 4.5

       ea_inode            ext4, 4.13

       large_dir           ext4, 4.13

       casefold            ext4, 5.2

       verity              ext4, 5.4

       stable_inodes       ext4, 5.5

SEE ALSO

       mke2fs(8), mke2fs.conf(5), e2fsck(8), dumpe2fs(8), tune2fs(8), debugfs(8), mount(8), chattr(1)

E2fsprogs version 1.47.0                          February 2023                                          EXT4(5)