1EXT4(5) File Formats Manual EXT4(5)
2
6 ext2 - the second extended file system
7 ext3 - the third extended file system
8 ext4 - the fourth extended file system
9
11 The second, third, and fourth extended file systems, or ext2, ext3, and
12 ext4 as they are commonly known, are Linux file systems that have his‐
13 torically been the default file system for many Linux distributions.
14 They are general purpose file systems that have been designed for
15 extensibility and backwards compatibility. In particular, file systems
16 previously intended for use with the ext2 and ext3 file systems can be
17 mounted using the ext4 file system driver, and indeed in many modern
18 Linux distributions, the ext4 file system driver has been configured to
19 handle mount requests for ext2 and ext3 file systems.
20
22 A file system formatted for ext2, ext3, or ext4 can have some collec‐
23 tion of the following file system feature flags enabled. Some of these
24 features are not supported by all implementations of the ext2, ext3,
25 and ext4 file system drivers, depending on Linux kernel version in use.
26 On other operating systems, such as the GNU/HURD or FreeBSD, only a
27 very restrictive set of file system features may be supported in their
28 implementations of ext2.
29 64bit
31 Enables the file system to be larger than 2^32 blocks. This
32 feature is set automatically, as needed, but it can be useful to
33 specify this feature explicitly if the file system might need to
34 be resized larger than 2^32 blocks, even if it was smaller than
35 that threshold when it was originally created. Note that some
36 older kernels and older versions of e2fsprogs will not support
37 file systems with this ext4 feature enabled.
38 bigalloc
40 This ext4 feature enables clustered block allocation, so that
41 the unit of allocation is a power of two number of blocks. That
42 is, each bit in the what had traditionally been known as the
43 block allocation bitmap now indicates whether a cluster is in
44 use or not, where a cluster is by default composed of 16 blocks.
45 This feature can decrease the time spent on doing block alloca‐
46 tion and brings smaller fragmentation, especially for large
47 files. The size can be specified using the mke2fs -C option.
48 Warning: The bigalloc feature is still under development, and
50 may not be fully supported with your kernel or may have various
51 bugs. Please see the web page http://ext4.wiki.ker‐
52 nel.org/index.php/Bigalloc for details. May clash with delayed
53 allocation (see nodelalloc mount option).
54 This feature requires that the extent feature be enabled.
56 dir_index
58 Use hashed b-trees to speed up name lookups in large directo‐
59 ries. This feature is supported by ext3 and ext4 file systems,
60 and is ignored by ext2 file systems.
61 dir_nlink
63 Normally, ext4 allows an inode to have no more than 65,000 hard
64 links. This applies to regular files as well as directories,
65 which means that there can be no more than 64,998 subdirectories
66 in a directory (because each of the '.' and '..' entries, as
67 well as the directory entry for the directory in its parent
68 directory counts as a hard link). This feature lifts this limit
69 by causing ext4 to use a link count of 1 to indicate that the
70 number of hard links to a directory is not known when the link
71 count might exceed the maximum count limit.
72 ea_inode
74 Normally, a file's extended attributes and associated metadata
75 must fit within the inode or the inode's associated extended
76 attribute block. This feature allows the value of each extended
77 attribute to be placed in the data blocks of a separate inode if
78 necessary, increasing the limit on the size and number of
79 extended attributes per file.
80 encrypt
82 This ext4 feature provides file-system level encryption of data
83 blocks and file names. The inode metadata (timestamps, file
84 size, user/group ownership, etc.) is not encrypted.
85 This feature is most useful on file systems with multiple users,
87 or where not all files should be encrypted. In many use cases,
88 especially on single-user systems, encryption at the block
89 device layer using dm-crypt may provide much better security.
90 ext_attr
92 This feature enables the use of extended attributes. This fea‐
93 ture is supported by ext2, ext3, and ext4.
94 extent
96 This ext4 feature allows the mapping of logical block numbers
97 for a particular inode to physical blocks on the storage device
98 to be stored using an extent tree, which is a more efficient
99 data structure than the traditional indirect block scheme used
100 by the ext2 and ext3 file systems. The use of the extent tree
101 decreases metadata block overhead, improves file system perfor‐
102 mance, and decreases the needed to run e2fsck(8) on the file
103 system. (Note: both extent and extents are accepted as valid
104 names for this feature for historical/backwards compatibility
105 reasons.)
106 extra_isize
108 This ext4 feature reserves a specific amount of space in each
109 inode for extended metadata such as nanosecond timestamps and
110 file creation time, even if the current kernel does not cur‐
111 rently need to reserve this much space. Without this feature,
112 the kernel will reserve the amount of space for features it cur‐
113 rently needs, and the rest may be consumed by extended
114 attributes.
115 For this feature to be useful the inode size must be 256 bytes
117 in size or larger.
118 filetype
120 This feature enables the storage of file type information in
121 directory entries. This feature is supported by ext2, ext3, and
122 ext4.
123 flex_bg
125 This ext4 feature allows the per-block group metadata (alloca‐
126 tion bitmaps and inode tables) to be placed anywhere on the
127 storage media. In addition, mke2fs will place the per-block
128 group metadata together starting at the first block group of
129 each "flex_bg group". The size of the flex_bg group can be
130 specified using the -G option.
131 has_journal
133 Create a journal to ensure filesystem consistency even across
134 unclean shutdowns. Setting the filesystem feature is equivalent
135 to using the -j option with mke2fs or tune2fs. This feature is
136 supported by ext3 and ext4, and ignored by the ext2 file system
137 driver.
138 huge_file
140 This ext4 feature allows files to be larger than 2 terabytes in
141 size.
142 inline_data
144 Allow data to be stored in the inode and extended attribute
145 area.
146 journal_dev
148 This feature is enabled on the superblock found on an external
149 journal device. The block size for the external journal must be
150 the same as the file system which uses it.
151 The external journal device can be used by a file system by
153 specifying the -J device=<external-device> option to mke2fs(8)
154 or tune2fs(8).
155 large_dir
157 This feature increases the limit on the number of files per
158 directory by raising the maximum size of directories and, for
159 hashed b-tree directories (see dir_index), the maximum height of
160 the hashed b-tree used to store the directory entries.
161 large_file
163 This feature flag is set automatically by modern kernels when a
164 file larger than 2 gigabytes is created. Very old kernels could
165 not handle large files, so this feature flag was used to pro‐
166 hibit those kernels from mounting file systems that they could
167 not understand.
168 metadata_csum
170 This ext4 feature enables metadata checksumming. This feature
171 stores checksums for all of the filesystem metadata (superblock,
172 group descriptor blocks, inode and block bitmaps, directories,
173 and extent tree blocks). The checksum algorithm used for the
174 metadata blocks is different than the one used for group
175 descriptors with the uninit_bg feature. These two features are
176 incompatible and metadata_csum will be used preferentially
177 instead of uninit_bg.
178 metadata_csum_seed
180 This feature allows the filesystem to store the metadata check‐
181 sum seed in the superblock, which allows the administrator to
182 change the UUID of a filesystem using the metadata_csum feature
183 while it is mounted.
184 meta_bg
186 This ext4 feature allows file systems to be resized on-line
187 without explicitly needing to reserve space for growth in the
188 size of the block group descriptors. This scheme is also used
189 to resize file systems which are larger than 2^32 blocks. It is
190 not recommended that this feature be set when a file system is
191 created, since this alternate method of storing the block group
192 descriptors will slow down the time needed to mount the file
193 system, and newer kernels can automatically set this feature as
194 necessary when doing an online resize and no more reserved space
195 is available in the resize inode.
196 mmp
198 This ext4 feature provides multiple mount protection (MMP). MMP
199 helps to protect the filesystem from being multiply mounted and
200 is useful in shared storage environments.
201 project
203 This ext4 feature provides project quota support. With this fea‐
204 ture, the project ID of inode will be managed when the filesys‐
205 tem is mounted.
206 quota
208 Create quota inodes (inode #3 for userquota and inode #4 for
209 group quota) and set them in the superblock. With this feature,
210 the quotas will be enabled automatically when the filesystem is
211 mounted.
212 Causes the quota files (i.e., user.quota and group.quota which
214 existed in the older quota design) to be hidden inodes.
215 resize_inode
217 This file system feature indicates that space has been reserved
218 so that the block group descriptor table can be extended while
219 resizing a mounted file system. The online resize operation is
220 carried out by the kernel, triggered by resize2fs(8). By
221 default mke2fs will attempt to reserve enough space so that the
222 filesystem may grow to 1024 times its initial size. This can be
223 changed using the resize extended option.
224 This feature requires that the sparse_super or sparse_super2
226 feature be enabled.
227 sparse_super
229 This file system feature is set on all modern ext2, ext3, and
230 ext4 file systems. It indicates that backup copies of the
231 superblock and block group descriptors are present only in a few
232 block groups, not all of them.
233 sparse_super2
235 This feature indicates that there will only be at most two
236 backup superblocks and block group descriptors. The block
237 groups used to store the backup superblock(s) and blockgroup
238 descriptor(s) are stored in the superblock, but typically, one
239 will be located at the beginning of block group #1, and one in
240 the last block group in the file system. This feature is essen‐
241 tially a more extreme version of sparse_super and is designed to
242 allow a much larger percentage of the disk to have contiguous
243 blocks available for data files.
244 uninit_bg
246 This ext4 file system feature indicates that the block group
247 descriptors will be protected using checksums, making it safe
248 for mke2fs(8) to create a file system without initializing all
249 of the block groups. The kernel will keep a high watermark of
250 unused inodes, and initialize inode tables and blocks lazily.
251 This feature speeds up the time to check the file system using
252 e2fsck(8), and it also speeds up the time required for mke2fs(8)
253 to create the file system.
254
256 This section describes mount options which are specific to ext2, ext3,
257 and ext4. Other generic mount options may be used as well; see
258 mount(8) for details.
259
261 The `ext2' filesystem is the standard Linux filesystem. Since Linux
262 2.5.46, for most mount options the default is determined by the
263 filesystem superblock. Set them with tune2fs(8).
264 acl|noacl
266 Support POSIX Access Control Lists (or not). See the acl(5)
267 manual page.
268 bsddf|minixdf
270 Set the behavior for the statfs system call. The minixdf behav‐
271 ior is to return in the f_blocks field the total number of
272 blocks of the filesystem, while the bsddf behavior (which is the
273 default) is to subtract the overhead blocks used by the ext2
274 filesystem and not available for file storage. Thus
275 % mount /k -o minixdf; df /k; umount /k
277 Filesystem 1024-blocks Used Available Capacity Mounted on
279 /dev/sda6 2630655 86954 2412169 3% /k
280 % mount /k -o bsddf; df /k; umount /k
282 Filesystem 1024-blocks Used Available Capacity Mounted on
284 /dev/sda6 2543714 13 2412169 0% /k
285 (Note that this example shows that one can add command line
287 options to the options given in /etc/fstab.)
288 check=none or nocheck
290 No checking is done at mount time. This is the default. This is
291 fast. It is wise to invoke e2fsck(8) every now and then, e.g.
292 at boot time. The non-default behavior is unsupported
293 (check=normal and check=strict options have been removed). Note
294 that these mount options don't have to be supported if ext4 ker‐
295 nel driver is used for ext2 and ext3 filesystems.
296 debug Print debugging info upon each (re)mount.
298 errors={continue|remount-ro|panic}
300 Define the behavior when an error is encountered. (Either
301 ignore errors and just mark the filesystem erroneous and con‐
302 tinue, or remount the filesystem read-only, or panic and halt
303 the system.) The default is set in the filesystem superblock,
304 and can be changed using tune2fs(8).
305 grpid|bsdgroups and nogrpid|sysvgroups
307 These options define what group id a newly created file gets.
308 When grpid is set, it takes the group id of the directory in
309 which it is created; otherwise (the default) it takes the fsgid
310 of the current process, unless the directory has the setgid bit
311 set, in which case it takes the gid from the parent directory,
312 and also gets the setgid bit set if it is a directory itself.
313 grpquota|noquota|quota|usrquota
315 The usrquota (same as quota) mount option enables user quota
316 support on the filesystem. grpquota enables group quotas sup‐
317 port. You need the quota utilities to actually enable and manage
318 the quota system.
319 nouid32
321 Disables 32-bit UIDs and GIDs. This is for interoperability
322 with older kernels which only store and expect 16-bit values.
323 oldalloc or orlov
325 Use old allocator or Orlov allocator for new inodes. Orlov is
326 default.
327 resgid=n and resuid=n
329 The ext2 filesystem reserves a certain percentage of the avail‐
330 able space (by default 5%, see mke2fs(8) and tune2fs(8)). These
331 options determine who can use the reserved blocks. (Roughly:
332 whoever has the specified uid, or belongs to the specified
333 group.)
334 sb=n Instead of using the normal superblock, use an alternative
336 superblock specified by n. This option is normally used when
337 the primary superblock has been corrupted. The location of
338 backup superblocks is dependent on the filesystem's blocksize,
339 the number of blocks per group, and features such as
340 sparse_super.
341 Additional backup superblocks can be determined by using the
343 mke2fs program using the -n option to print out where the
344 superblocks exist, supposing mke2fs is supplied with arguments
345 that are consistent with the filesystem's layout (e.g. block‐
346 size, blocks per group, sparse_super, etc.).
347 The block number here uses 1 k units. Thus, if you want to use
349 logical block 32768 on a filesystem with 4 k blocks, use
350 "sb=131072".
351 user_xattr|nouser_xattr
353 Support "user." extended attributes (or not).
354
358 The ext3 filesystem is a version of the ext2 filesystem which has been
359 enhanced with journaling. It supports the same options as ext2 as well
360 as the following additions:
361 journal_dev=devnum/journal_path=path
363 When the external journal device's major/minor numbers have
364 changed, these options allow the user to specify the new journal
365 location. The journal device is identified either through its
366 new major/minor numbers encoded in devnum, or via a path to the
367 device.
368 norecovery/noload
370 Don't load the journal on mounting. Note that if the filesystem
371 was not unmounted cleanly, skipping the journal replay will lead
372 to the filesystem containing inconsistencies that can lead to
373 any number of problems.
374 data={journal|ordered|writeback}
376 Specifies the journaling mode for file data. Metadata is always
377 journaled. To use modes other than ordered on the root filesys‐
378 tem, pass the mode to the kernel as boot parameter, e.g. root‐
379 flags=data=journal.
380 journal
382 All data is committed into the journal prior to being
383 written into the main filesystem.
384 ordered
386 This is the default mode. All data is forced directly
387 out to the main file system prior to its metadata being
388 committed to the journal.
389 writeback
391 Data ordering is not preserved – data may be written into
392 the main filesystem after its metadata has been committed
393 to the journal. This is rumoured to be the highest-
394 throughput option. It guarantees internal filesystem
395 integrity, however it can allow old data to appear in
396 files after a crash and journal recovery.
397 data_err=ignore
399 Just print an error message if an error occurs in a file data
400 buffer in ordered mode.
401 data_err=abort
403 Abort the journal if an error occurs in a file data buffer in
404 ordered mode.
405 barrier=0 / barrier=1
407 This disables / enables the use of write barriers in the jbd
408 code. barrier=0 disables, barrier=1 enables (default). This
409 also requires an IO stack which can support barriers, and if jbd
410 gets an error on a barrier write, it will disable barriers again
411 with a warning. Write barriers enforce proper on-disk ordering
412 of journal commits, making volatile disk write caches safe to
413 use, at some performance penalty. If your disks are battery-
414 backed in one way or another, disabling barriers may safely
415 improve performance.
416 commit=nrsec
418 Start a journal commit every nrsec seconds. The default value
419 is 5 seconds. Zero means default.
420 user_xattr
422 Enable Extended User Attributes. See the attr(5) manual page.
423 jqfmt={vfsold|vfsv0|vfsv1}
425 Apart from the old quota system (as in ext2, jqfmt=vfsold aka
426 version 1 quota) ext3 also supports journaled quotas (version 2
427 quota). jqfmt=vfsv0 or jqfmt=vfsv1 enables journaled quotas.
428 Journaled quotas have the advantage that even after a crash no
429 quota check is required. When the quota filesystem feature is
430 enabled, journaled quotas are used automatically, and this mount
431 option is ignored.
432 usrjquota=aquota.user|grpjquota=aquota.group
434 For journaled quotas (jqfmt=vfsv0 or jqfmt=vfsv1), the mount
435 options usrjquota=aquota.user and grpjquota=aquota.group are
436 required to tell the quota system which quota database files to
437 use. When the quota filesystem feature is enabled, journaled
438 quotas are used automatically, and this mount option is ignored.
439
442 The ext4 filesystem is an advanced level of the ext3 filesystem which
443 incorporates scalability and reliability enhancements for supporting
444 large filesystem.
445 The options journal_dev, journal_path, norecovery, noload, data, com‐
447 mit, orlov, oldalloc, [no]user_xattr, [no]acl, bsddf, minixdf, debug,
448 errors, data_err, grpid, bsdgroups, nogrpid, sysvgroups, resgid,
449 resuid, sb, quota, noquota, nouid32, grpquota, usrquota, usrjquota,
450 grpjquota, and jqfmt are backwardly compatible with ext3 or ext2.
451 journal_checksum | nojournal_checksum
453 The journal_checksum option enables checksumming of the journal
454 transactions. This will allow the recovery code in e2fsck and
455 the kernel to detect corruption in the kernel. It is a compati‐
456 ble change and will be ignored by older kernels.
457 journal_async_commit
459 Commit block can be written to disk without waiting for descrip‐
460 tor blocks. If enabled older kernels cannot mount the device.
461 This will enable 'journal_checksum' internally.
462 barrier=0 / barrier=1 / barrier / nobarrier
464 These mount options have the same effect as in ext3. The mount
465 options "barrier" and "nobarrier" are added for consistency with
466 other ext4 mount options.
467 The ext4 filesystem enables write barriers by default.
469 inode_readahead_blks=n
471 This tuning parameter controls the maximum number of inode table
472 blocks that ext4's inode table readahead algorithm will pre-read
473 into the buffer cache. The value must be a power of 2. The
474 default value is 32 blocks.
475 stripe=n
477 Number of filesystem blocks that mballoc will try to use for
478 allocation size and alignment. For RAID5/6 systems this should
479 be the number of data disks * RAID chunk size in filesystem
480 blocks.
481 delalloc
483 Deferring block allocation until write-out time.
484 nodelalloc
486 Disable delayed allocation. Blocks are allocated when data is
487 copied from user to page cache.
488 max_batch_time=usec
490 Maximum amount of time ext4 should wait for additional filesys‐
491 tem operations to be batch together with a synchronous write
492 operation. Since a synchronous write operation is going to force
493 a commit and then a wait for the I/O complete, it doesn't cost
494 much, and can be a huge throughput win, we wait for a small
495 amount of time to see if any other transactions can piggyback on
496 the synchronous write. The algorithm used is designed to auto‐
497 matically tune for the speed of the disk, by measuring the
498 amount of time (on average) that it takes to finish committing a
499 transaction. Call this time the "commit time". If the time that
500 the transaction has been running is less than the commit time,
501 ext4 will try sleeping for the commit time to see if other oper‐
502 ations will join the transaction. The commit time is capped by
503 the max_batch_time, which defaults to 15000 µs (15 ms). This
504 optimization can be turned off entirely by setting
505 max_batch_time to 0.
506 min_batch_time=usec
508 This parameter sets the commit time (as described above) to be
509 at least min_batch_time. It defaults to zero microseconds.
510 Increasing this parameter may improve the throughput of multi-
511 threaded, synchronous workloads on very fast disks, at the cost
512 of increasing latency.
513 journal_ioprio=prio
515 The I/O priority (from 0 to 7, where 0 is the highest priority)
516 which should be used for I/O operations submitted by kjournald2
517 during a commit operation. This defaults to 3, which is a
518 slightly higher priority than the default I/O priority.
519 abort Simulate the effects of calling ext4_abort() for debugging pur‐
521 poses. This is normally used while remounting a filesystem
522 which is already mounted.
523 auto_da_alloc|noauto_da_alloc
525 Many broken applications don't use fsync() when replacing exist‐
526 ing files via patterns such as
527 fd = open("foo.new")/write(fd,...)/close(fd)/ rename("foo.new",
529 "foo")
530 or worse yet
532 fd = open("foo", O_TRUNC)/write(fd,...)/close(fd).
534 If auto_da_alloc is enabled, ext4 will detect the replace-via-
536 rename and replace-via-truncate patterns and force that any
537 delayed allocation blocks are allocated such that at the next
538 journal commit, in the default data=ordered mode, the data
539 blocks of the new file are forced to disk before the rename()
540 operation is committed. This provides roughly the same level of
541 guarantees as ext3, and avoids the "zero-length" problem that
542 can happen when a system crashes before the delayed allocation
543 blocks are forced to disk.
544 noinit_itable
546 Do not initialize any uninitialized inode table blocks in the
547 background. This feature may be used by installation CD's so
548 that the install process can complete as quickly as possible;
549 the inode table initialization process would then be deferred
550 until the next time the filesystem is mounted.
551 init_itable=n
553 The lazy itable init code will wait n times the number of mil‐
554 liseconds it took to zero out the previous block group's inode
555 table. This minimizes the impact on system performance while the
556 filesystem's inode table is being initialized.
557 discard/nodiscard
559 Controls whether ext4 should issue discard/TRIM commands to the
560 underlying block device when blocks are freed. This is useful
561 for SSD devices and sparse/thinly-provisioned LUNs, but it is
562 off by default until sufficient testing has been done.
563 block_validity/noblock_validity
565 This option enables/disables the in-kernel facility for tracking
566 filesystem metadata blocks within internal data structures. This
567 allows multi-block allocator and other routines to quickly
568 locate extents which might overlap with filesystem metadata
569 blocks. This option is intended for debugging purposes and since
570 it negatively affects the performance, it is off by default.
571 dioread_lock/dioread_nolock
573 Controls whether or not ext4 should use the DIO read locking. If
574 the dioread_nolock option is specified ext4 will allocate unini‐
575 tialized extent before buffer write and convert the extent to
576 initialized after IO completes. This approach allows ext4 code
577 to avoid using inode mutex, which improves scalability on high
578 speed storages. However this does not work with data journaling
579 and dioread_nolock option will be ignored with kernel warning.
580 Note that dioread_nolock code path is only used for extent-based
581 files. Because of the restrictions this options comprises it is
582 off by default (e.g. dioread_lock).
583 max_dir_size_kb=n
585 This limits the size of the directories so that any attempt to
586 expand them beyond the specified limit in kilobytes will cause
587 an ENOSPC error. This is useful in memory-constrained environ‐
588 ments, where a very large directory can cause severe performance
589 problems or even provoke the Out Of Memory killer. (For example,
590 if there is only 512 MB memory available, a 176 MB directory may
591 seriously cramp the system's style.)
592 i_version
594 Enable 64-bit inode version support. This option is off by
595 default.
596 nombcache
598 This option disables use of mbcache for extended attribute dedu‐
599 plication. On systems where extended attributes are rarely or
600 never shared between files, use of mbcache for deduplication
601 adds unnecessary computational overhead.
602 prjquota
604 The prjquota mount option enables project quota support on the
605 filesystem. You need the quota utilities to actually enable and
606 manage the quota system. This mount option requires the project
607 filesystem feature.
608
611 The ext2, ext3, and ext4 filesystems support setting the following file
612 attributes on Linux systems using the chattr(1) utility:
613 a - append only
615 A - no atime updates
617 d - no dump
619 D - synchronous directory updates
621 i - immutable
623 S - synchronous updates
625 u - undeletable
627 In addition, the ext3 and ext4 filesystems support the following flag:
629 j - data journaling
631 Finally, the ext4 filesystem also supports the following flag:
633 e - extents format
635 For descriptions of these attribute flags, please refer to the
637 chattr(1) man page.
638
640 This section lists the file system driver (e.g., ext2, ext3, ext4) and
641 upstream kernel version where a particular file system feature was sup‐
642 ported. Note that in some cases the feature was present in earlier
643 kernel versions, but there were known, serious bugs. In other cases
644 the feature may still be considered in an experimental state. Finally,
645 note that some distributions may have backported features into older
646 kernels; in particular the kernel versions in certain "enterprise dis‐
647 tributions" can be extremely misleading.
648 filetype ext2, 2.2.0
650 sparse_super ext2, 2.2.0
652 large_file ext2, 2.2.0
654 has_journal ext3, 2.4.15
656 ext_attr ext2/ext3, 2.6.0
658 dir_index ext3, 2.6.0
660 resize_inode ext3, 2.6.10 (online resizing)
662 64bit ext4, 2.6.28
664 dir_nlink ext4, 2.6.28
666 extent ext4, 2.6.28
668 extra_isize ext4, 2.6.28
670 flex_bg ext4, 2.6.28
672 huge_file ext4, 2.6.28
674 meta_bg ext4, 2.6.28
676 uninit_bg ext4, 2.6.28
678 mmp ext4, 3.0
680 bigalloc ext4, 3.2
682 quota ext4, 3.6
684 inline_data ext4, 3.8
686 sparse_super2 ext4, 3.16
688 metadata_csum ext4, 3.18
690 encrypt ext4, 4.1
692 metadata_csum_seed ext4, 4.4
694 project ext4, 4.5
696 ea_inode ext4, 4.13
698 large_dir ext4, 4.13
700
702 mke2fs(8), mke2fs.conf(5), e2fsck(8), dumpe2fs(8), tune2fs(8),
703 debugfs(8), mount(8), chattr(1)
704E2fsprogs version 1.44.6 March 2019 EXT4(5)