ext4(5) — Linux manual page

NAME | DESCRIPTION | FILE SYSTEM FEATURES | MOUNT OPTIONS | Mount options for ext2 | Mount options for ext3 | Mount options for ext4 | FILE ATTRIBUTES | KERNEL SUPPORT | SEE ALSO | COLOPHON

EXT4(5)                    File Formats Manual                   EXT4(5)

NAME         top

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

DESCRIPTION         top

       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         top

       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 filesystem consistency even
              across unclean shutdowns.  Setting the filesystem 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 filesystem
              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 filesystem to store the metadata
              checksum seed in the superblock, which allows the
              administrator to change the UUID of a filesystem 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 filesystem 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 filesystem 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 filesystem 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 filesystem 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 filesystem's inode numbers and UUID as stable.
              resize2fs(8) will not allow shrinking a filesystem 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         top

       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         top

       The `ext2' filesystem is the standard Linux filesystem.  Since
       Linux 2.5.46, for most mount options the default is determined by
       the filesystem 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 filesystem, while the bsddf
              behavior (which is the default) is to subtract the
              overhead blocks used by the ext2 filesystem and not
              available for file storage. Thus

              % mount /k -o minixdf; df /k; umount /k

              Filesystem  1024-blocks   Used  Available  Capacity  Mounted on
              /dev/sda6     2630655    86954   2412169      3%     /k

              % mount /k -o bsddf; df /k; umount /k

              Filesystem  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 filesystems.

       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 filesystem erroneous and
              continue, or remount the filesystem read-only, or panic
              and halt the system.)  The default is set in the
              filesystem 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 filesystem. 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 filesystem 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
              filesystem'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 filesystem'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 filesystem with 4 k blocks,
              use "sb=131072".

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

Mount options for ext3         top

       The ext3 filesystem is a version of the ext2 filesystem 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
              filesystem was not unmounted cleanly, skipping the journal
              replay will lead to the filesystem 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 filesystem, 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 filesystem.

              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 filesystem after its metadata
                     has been committed to the journal.  This is
                     rumoured to be the highest-throughput option.  It
                     guarantees internal filesystem 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 filesystem 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
              filesystem feature is enabled, journaled quotas are used
              automatically, and this mount option is ignored.

Mount options for ext4         top

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

       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 filesystem 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 filesystem 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 filesystem 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
              filesystem 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
              filesystem 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 filesystem 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 filesystem'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 filesystem metadata blocks within internal data
              structures. This allows multi-block allocator and other
              routines to quickly locate extents which might overlap
              with filesystem 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 filesystem.  You need the quota utilities to actually
              enable and manage the quota system.  This mount option
              requires the project filesystem feature.

FILE ATTRIBUTES         top

       The ext2, ext3, and ext4 filesystems 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 filesystems support the following
       flag:

       j - data journaling

       Finally, the ext4 filesystem also supports the following flag:

       e - extents format

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

KERNEL SUPPORT         top

       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         top

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

COLOPHON         top

       This page is part of the e2fsprogs (utilities for ext2/3/4
       filesystems) project.  Information about the project can be found
       at ⟨http://e2fsprogs.sourceforge.net/⟩.  It is not known how to
       report bugs for this man page; if you know, please send a mail to
       man-pages@man7.org.  This page was obtained from the project's
       upstream Git repository
       ⟨git://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git⟩ on
       2021-04-01.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-02-28.)  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to man-pages@man7.org

E2fsprogs version 1.46.2      February 2021                      EXT4(5)

Pages that refer to this page: chattr(1)fuse2fs(1)ioctl_iflags(2)link(2)filesystems(5)debugfs(8)dmstats(8)dumpe2fs(8)mke2fs(8)mount(8)systemd-makefs@.service(8)tune2fs(8)