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 casefold
58 This ext4 feature provides file system level character encoding
59 support for directories with the casefold (+F) flag enabled.
60 This feature is name-preserving on the disk, but it allows
61 applications to lookup for a file in the file system using an
62 encoding equivalent version of the file name.
63 dir_index
65 Use hashed b-trees to speed up name lookups in large directo‐
66 ries. This feature is supported by ext3 and ext4 file systems,
67 and is ignored by ext2 file systems.
68 dir_nlink
70 Normally, ext4 allows an inode to have no more than 65,000 hard
71 links. This applies to regular files as well as directories,
72 which means that there can be no more than 64,998 subdirectories
73 in a directory (because each of the '.' and '..' entries, as
74 well as the directory entry for the directory in its parent
75 directory counts as a hard link). This feature lifts this limit
76 by causing ext4 to use a link count of 1 to indicate that the
77 number of hard links to a directory is not known when the link
78 count might exceed the maximum count limit.
79 ea_inode
81 Normally, a file's extended attributes and associated metadata
82 must fit within the inode or the inode's associated extended
83 attribute block. This feature allows the value of each extended
84 attribute to be placed in the data blocks of a separate inode if
85 necessary, increasing the limit on the size and number of
86 extended attributes per file.
87 encrypt
89 Enables support for file-system level encryption of data blocks
90 and file names. The inode metadata (timestamps, file size,
91 user/group ownership, etc.) is not encrypted.
92 This feature is most useful on file systems with multiple users,
94 or where not all files should be encrypted. In many use cases,
95 especially on single-user systems, encryption at the block
96 device layer using dm-crypt may provide much better security.
97 ext_attr
99 This feature enables the use of extended attributes. This fea‐
100 ture is supported by ext2, ext3, and ext4.
101 extent
103 This ext4 feature allows the mapping of logical block numbers
104 for a particular inode to physical blocks on the storage device
105 to be stored using an extent tree, which is a more efficient
106 data structure than the traditional indirect block scheme used
107 by the ext2 and ext3 file systems. The use of the extent tree
108 decreases metadata block overhead, improves file system perfor‐
109 mance, and decreases the needed to run e2fsck(8) on the file
110 system. (Note: both extent and extents are accepted as valid
111 names for this feature for historical/backwards compatibility
112 reasons.)
113 extra_isize
115 This ext4 feature reserves a specific amount of space in each
116 inode for extended metadata such as nanosecond timestamps and
117 file creation time, even if the current kernel does not cur‐
118 rently need to reserve this much space. Without this feature,
119 the kernel will reserve the amount of space for features it cur‐
120 rently needs, and the rest may be consumed by extended
121 attributes.
122 For this feature to be useful the inode size must be 256 bytes
124 in size or larger.
125 filetype
127 This feature enables the storage of file type information in
128 directory entries. This feature is supported by ext2, ext3, and
129 ext4.
130 flex_bg
132 This ext4 feature allows the per-block group metadata (alloca‐
133 tion bitmaps and inode tables) to be placed anywhere on the
134 storage media. In addition, mke2fs will place the per-block
135 group metadata together starting at the first block group of
136 each "flex_bg group". The size of the flex_bg group can be
137 specified using the -G option.
138 has_journal
140 Create a journal to ensure filesystem consistency even across
141 unclean shutdowns. Setting the filesystem feature is equivalent
142 to using the -j option with mke2fs or tune2fs. This feature is
143 supported by ext3 and ext4, and ignored by the ext2 file system
144 driver.
145 huge_file
147 This ext4 feature allows files to be larger than 2 terabytes in
148 size.
149 inline_data
151 Allow data to be stored in the inode and extended attribute
152 area.
153 journal_dev
155 This feature is enabled on the superblock found on an external
156 journal device. The block size for the external journal must be
157 the same as the file system which uses it.
158 The external journal device can be used by a file system by
160 specifying the -J device=<external-device> option to mke2fs(8)
161 or tune2fs(8).
162 large_dir
164 This feature increases the limit on the number of files per
165 directory by raising the maximum size of directories and, for
166 hashed b-tree directories (see dir_index), the maximum height of
167 the hashed b-tree used to store the directory entries.
168 large_file
170 This feature flag is set automatically by modern kernels when a
171 file larger than 2 gigabytes is created. Very old kernels could
172 not handle large files, so this feature flag was used to pro‐
173 hibit those kernels from mounting file systems that they could
174 not understand.
175 metadata_csum
177 This ext4 feature enables metadata checksumming. This feature
178 stores checksums for all of the filesystem metadata (superblock,
179 group descriptor blocks, inode and block bitmaps, directories,
180 and extent tree blocks). The checksum algorithm used for the
181 metadata blocks is different than the one used for group
182 descriptors with the uninit_bg feature. These two features are
183 incompatible and metadata_csum will be used preferentially
184 instead of uninit_bg.
185 metadata_csum_seed
187 This feature allows the filesystem to store the metadata check‐
188 sum seed in the superblock, which allows the administrator to
189 change the UUID of a filesystem using the metadata_csum feature
190 while it is mounted.
191 meta_bg
193 This ext4 feature allows file systems to be resized on-line
194 without explicitly needing to reserve space for growth in the
195 size of the block group descriptors. This scheme is also used
196 to resize file systems which are larger than 2^32 blocks. It is
197 not recommended that this feature be set when a file system is
198 created, since this alternate method of storing the block group
199 descriptors will slow down the time needed to mount the file
200 system, and newer kernels can automatically set this feature as
201 necessary when doing an online resize and no more reserved space
202 is available in the resize inode.
203 mmp
205 This ext4 feature provides multiple mount protection (MMP). MMP
206 helps to protect the filesystem from being multiply mounted and
207 is useful in shared storage environments.
208 project
210 This ext4 feature provides project quota support. With this fea‐
211 ture, the project ID of inode will be managed when the filesys‐
212 tem is mounted.
213 quota
215 Create quota inodes (inode #3 for userquota and inode #4 for
216 group quota) and set them in the superblock. With this feature,
217 the quotas will be enabled automatically when the filesystem is
218 mounted.
219 Causes the quota files (i.e., user.quota and group.quota which
221 existed in the older quota design) to be hidden inodes.
222 resize_inode
224 This file system feature indicates that space has been reserved
225 so that the block group descriptor table can be extended while
226 resizing a mounted file system. The online resize operation is
227 carried out by the kernel, triggered by resize2fs(8). By
228 default mke2fs will attempt to reserve enough space so that the
229 filesystem may grow to 1024 times its initial size. This can be
230 changed using the resize extended option.
231 This feature requires that the sparse_super or sparse_super2
233 feature be enabled.
234 sparse_super
236 This file system feature is set on all modern ext2, ext3, and
237 ext4 file systems. It indicates that backup copies of the
238 superblock and block group descriptors are present only in a few
239 block groups, not all of them.
240 sparse_super2
242 This feature indicates that there will only be at most two
243 backup superblocks and block group descriptors. The block
244 groups used to store the backup superblock(s) and blockgroup
245 descriptor(s) are stored in the superblock, but typically, one
246 will be located at the beginning of block group #1, and one in
247 the last block group in the file system. This feature is essen‐
248 tially a more extreme version of sparse_super and is designed to
249 allow a much larger percentage of the disk to have contiguous
250 blocks available for data files.
251 uninit_bg
253 This ext4 file system feature indicates that the block group
254 descriptors will be protected using checksums, making it safe
255 for mke2fs(8) to create a file system without initializing all
256 of the block groups. The kernel will keep a high watermark of
257 unused inodes, and initialize inode tables and blocks lazily.
258 This feature speeds up the time to check the file system using
259 e2fsck(8), and it also speeds up the time required for mke2fs(8)
260 to create the file system.
261 verity
263 Enables support for verity protected files. Verity files are
264 readonly, and their data is transparently verified against a
265 Merkle tree hidden past the end of the file. Using the Merkle
266 tree's root hash, a verity file can be efficiently authenti‐
267 cated, independent of the file's size.
268 This feature is most useful for authenticating important read-
270 only files on read-write file systems. If the file system
271 itself is read-only, then using dm-verity to authenticate the
272 entire block device may provide much better security.
273
275 This section describes mount options which are specific to ext2, ext3,
276 and ext4. Other generic mount options may be used as well; see
277 mount(8) for details.
278
280 The `ext2' filesystem is the standard Linux filesystem. Since Linux
281 2.5.46, for most mount options the default is determined by the
282 filesystem superblock. Set them with tune2fs(8).
283 acl|noacl
285 Support POSIX Access Control Lists (or not). See the acl(5)
286 manual page.
287 bsddf|minixdf
289 Set the behavior for the statfs system call. The minixdf behav‐
290 ior is to return in the f_blocks field the total number of
291 blocks of the filesystem, while the bsddf behavior (which is the
292 default) is to subtract the overhead blocks used by the ext2
293 filesystem and not available for file storage. Thus
294 % mount /k -o minixdf; df /k; umount /k
296 Filesystem 1024-blocks Used Available Capacity Mounted on
298 /dev/sda6 2630655 86954 2412169 3% /k
299 % mount /k -o bsddf; df /k; umount /k
301 Filesystem 1024-blocks Used Available Capacity Mounted on
303 /dev/sda6 2543714 13 2412169 0% /k
304 (Note that this example shows that one can add command line
306 options to the options given in /etc/fstab.)
307 check=none or nocheck
309 No checking is done at mount time. This is the default. This is
310 fast. It is wise to invoke e2fsck(8) every now and then, e.g.
311 at boot time. The non-default behavior is unsupported
312 (check=normal and check=strict options have been removed). Note
313 that these mount options don't have to be supported if ext4 ker‐
314 nel driver is used for ext2 and ext3 filesystems.
315 debug Print debugging info upon each (re)mount.
317 errors={continue|remount-ro|panic}
319 Define the behavior when an error is encountered. (Either
320 ignore errors and just mark the filesystem erroneous and con‐
321 tinue, or remount the filesystem read-only, or panic and halt
322 the system.) The default is set in the filesystem superblock,
323 and can be changed using tune2fs(8).
324 grpid|bsdgroups and nogrpid|sysvgroups
326 These options define what group id a newly created file gets.
327 When grpid is set, it takes the group id of the directory in
328 which it is created; otherwise (the default) it takes the fsgid
329 of the current process, unless the directory has the setgid bit
330 set, in which case it takes the gid from the parent directory,
331 and also gets the setgid bit set if it is a directory itself.
332 grpquota|noquota|quota|usrquota
334 The usrquota (same as quota) mount option enables user quota
335 support on the filesystem. grpquota enables group quotas sup‐
336 port. You need the quota utilities to actually enable and manage
337 the quota system.
338 nouid32
340 Disables 32-bit UIDs and GIDs. This is for interoperability
341 with older kernels which only store and expect 16-bit values.
342 oldalloc or orlov
344 Use old allocator or Orlov allocator for new inodes. Orlov is
345 default.
346 resgid=n and resuid=n
348 The ext2 filesystem reserves a certain percentage of the avail‐
349 able space (by default 5%, see mke2fs(8) and tune2fs(8)). These
350 options determine who can use the reserved blocks. (Roughly:
351 whoever has the specified uid, or belongs to the specified
352 group.)
353 sb=n Instead of using the normal superblock, use an alternative
355 superblock specified by n. This option is normally used when
356 the primary superblock has been corrupted. The location of
357 backup superblocks is dependent on the filesystem's blocksize,
358 the number of blocks per group, and features such as
359 sparse_super.
360 Additional backup superblocks can be determined by using the
362 mke2fs program using the -n option to print out where the
363 superblocks exist, supposing mke2fs is supplied with arguments
364 that are consistent with the filesystem's layout (e.g. block‐
365 size, blocks per group, sparse_super, etc.).
366 The block number here uses 1 k units. Thus, if you want to use
368 logical block 32768 on a filesystem with 4 k blocks, use
369 "sb=131072".
370 user_xattr|nouser_xattr
372 Support "user." extended attributes (or not).
373
377 The ext3 filesystem is a version of the ext2 filesystem which has been
378 enhanced with journaling. It supports the same options as ext2 as well
379 as the following additions:
380 journal_dev=devnum/journal_path=path
382 When the external journal device's major/minor numbers have
383 changed, these options allow the user to specify the new journal
384 location. The journal device is identified either through its
385 new major/minor numbers encoded in devnum, or via a path to the
386 device.
387 norecovery/noload
389 Don't load the journal on mounting. Note that if the filesystem
390 was not unmounted cleanly, skipping the journal replay will lead
391 to the filesystem containing inconsistencies that can lead to
392 any number of problems.
393 data={journal|ordered|writeback}
395 Specifies the journaling mode for file data. Metadata is always
396 journaled. To use modes other than ordered on the root filesys‐
397 tem, pass the mode to the kernel as boot parameter, e.g. root‐
398 flags=data=journal.
399 journal
401 All data is committed into the journal prior to being
402 written into the main filesystem.
403 ordered
405 This is the default mode. All data is forced directly
406 out to the main file system prior to its metadata being
407 committed to the journal.
408 writeback
410 Data ordering is not preserved – data may be written into
411 the main filesystem after its metadata has been committed
412 to the journal. This is rumoured to be the highest-
413 throughput option. It guarantees internal filesystem
414 integrity, however it can allow old data to appear in
415 files after a crash and journal recovery.
416 data_err=ignore
418 Just print an error message if an error occurs in a file data
419 buffer in ordered mode.
420 data_err=abort
422 Abort the journal if an error occurs in a file data buffer in
423 ordered mode.
424 barrier=0 / barrier=1
426 This disables / enables the use of write barriers in the jbd
427 code. barrier=0 disables, barrier=1 enables (default). This
428 also requires an IO stack which can support barriers, and if jbd
429 gets an error on a barrier write, it will disable barriers again
430 with a warning. Write barriers enforce proper on-disk ordering
431 of journal commits, making volatile disk write caches safe to
432 use, at some performance penalty. If your disks are battery-
433 backed in one way or another, disabling barriers may safely
434 improve performance.
435 commit=nrsec
437 Start a journal commit every nrsec seconds. The default value
438 is 5 seconds. Zero means default.
439 user_xattr
441 Enable Extended User Attributes. See the attr(5) manual page.
442 jqfmt={vfsold|vfsv0|vfsv1}
444 Apart from the old quota system (as in ext2, jqfmt=vfsold aka
445 version 1 quota) ext3 also supports journaled quotas (version 2
446 quota). jqfmt=vfsv0 or jqfmt=vfsv1 enables journaled quotas.
447 Journaled quotas have the advantage that even after a crash no
448 quota check is required. When the quota filesystem feature is
449 enabled, journaled quotas are used automatically, and this mount
450 option is ignored.
451 usrjquota=aquota.user|grpjquota=aquota.group
453 For journaled quotas (jqfmt=vfsv0 or jqfmt=vfsv1), the mount
454 options usrjquota=aquota.user and grpjquota=aquota.group are
455 required to tell the quota system which quota database files to
456 use. When the quota filesystem feature is enabled, journaled
457 quotas are used automatically, and this mount option is ignored.
458
461 The ext4 filesystem is an advanced level of the ext3 filesystem which
462 incorporates scalability and reliability enhancements for supporting
463 large filesystem.
464 The options journal_dev, journal_path, norecovery, noload, data, com‐
466 mit, orlov, oldalloc, [no]user_xattr, [no]acl, bsddf, minixdf, debug,
467 errors, data_err, grpid, bsdgroups, nogrpid, sysvgroups, resgid,
468 resuid, sb, quota, noquota, nouid32, grpquota, usrquota, usrjquota,
469 grpjquota, and jqfmt are backwardly compatible with ext3 or ext2.
470 journal_checksum | nojournal_checksum
472 The journal_checksum option enables checksumming of the journal
473 transactions. This will allow the recovery code in e2fsck and
474 the kernel to detect corruption in the kernel. It is a compati‐
475 ble change and will be ignored by older kernels.
476 journal_async_commit
478 Commit block can be written to disk without waiting for descrip‐
479 tor blocks. If enabled older kernels cannot mount the device.
480 This will enable 'journal_checksum' internally.
481 barrier=0 / barrier=1 / barrier / nobarrier
483 These mount options have the same effect as in ext3. The mount
484 options "barrier" and "nobarrier" are added for consistency with
485 other ext4 mount options.
486 The ext4 filesystem enables write barriers by default.
488 inode_readahead_blks=n
490 This tuning parameter controls the maximum number of inode table
491 blocks that ext4's inode table readahead algorithm will pre-read
492 into the buffer cache. The value must be a power of 2. The
493 default value is 32 blocks.
494 stripe=n
496 Number of filesystem blocks that mballoc will try to use for
497 allocation size and alignment. For RAID5/6 systems this should
498 be the number of data disks * RAID chunk size in filesystem
499 blocks.
500 delalloc
502 Deferring block allocation until write-out time.
503 nodelalloc
505 Disable delayed allocation. Blocks are allocated when data is
506 copied from user to page cache.
507 max_batch_time=usec
509 Maximum amount of time ext4 should wait for additional filesys‐
510 tem operations to be batch together with a synchronous write
511 operation. Since a synchronous write operation is going to force
512 a commit and then a wait for the I/O complete, it doesn't cost
513 much, and can be a huge throughput win, we wait for a small
514 amount of time to see if any other transactions can piggyback on
515 the synchronous write. The algorithm used is designed to auto‐
516 matically tune for the speed of the disk, by measuring the
517 amount of time (on average) that it takes to finish committing a
518 transaction. Call this time the "commit time". If the time that
519 the transaction has been running is less than the commit time,
520 ext4 will try sleeping for the commit time to see if other oper‐
521 ations will join the transaction. The commit time is capped by
522 the max_batch_time, which defaults to 15000 µs (15 ms). This
523 optimization can be turned off entirely by setting
524 max_batch_time to 0.
525 min_batch_time=usec
527 This parameter sets the commit time (as described above) to be
528 at least min_batch_time. It defaults to zero microseconds.
529 Increasing this parameter may improve the throughput of multi-
530 threaded, synchronous workloads on very fast disks, at the cost
531 of increasing latency.
532 journal_ioprio=prio
534 The I/O priority (from 0 to 7, where 0 is the highest priority)
535 which should be used for I/O operations submitted by kjournald2
536 during a commit operation. This defaults to 3, which is a
537 slightly higher priority than the default I/O priority.
538 abort Simulate the effects of calling ext4_abort() for debugging pur‐
540 poses. This is normally used while remounting a filesystem
541 which is already mounted.
542 auto_da_alloc|noauto_da_alloc
544 Many broken applications don't use fsync() when replacing exist‐
545 ing files via patterns such as
546 fd = open("foo.new")/write(fd,...)/close(fd)/ rename("foo.new",
548 "foo")
549 or worse yet
551 fd = open("foo", O_TRUNC)/write(fd,...)/close(fd).
553 If auto_da_alloc is enabled, ext4 will detect the replace-via-
555 rename and replace-via-truncate patterns and force that any
556 delayed allocation blocks are allocated such that at the next
557 journal commit, in the default data=ordered mode, the data
558 blocks of the new file are forced to disk before the rename()
559 operation is committed. This provides roughly the same level of
560 guarantees as ext3, and avoids the "zero-length" problem that
561 can happen when a system crashes before the delayed allocation
562 blocks are forced to disk.
563 noinit_itable
565 Do not initialize any uninitialized inode table blocks in the
566 background. This feature may be used by installation CD's so
567 that the install process can complete as quickly as possible;
568 the inode table initialization process would then be deferred
569 until the next time the filesystem is mounted.
570 init_itable=n
572 The lazy itable init code will wait n times the number of mil‐
573 liseconds it took to zero out the previous block group's inode
574 table. This minimizes the impact on system performance while the
575 filesystem's inode table is being initialized.
576 discard/nodiscard
578 Controls whether ext4 should issue discard/TRIM commands to the
579 underlying block device when blocks are freed. This is useful
580 for SSD devices and sparse/thinly-provisioned LUNs, but it is
581 off by default until sufficient testing has been done.
582 block_validity/noblock_validity
584 This option enables/disables the in-kernel facility for tracking
585 filesystem metadata blocks within internal data structures. This
586 allows multi-block allocator and other routines to quickly
587 locate extents which might overlap with filesystem metadata
588 blocks. This option is intended for debugging purposes and since
589 it negatively affects the performance, it is off by default.
590 dioread_lock/dioread_nolock
592 Controls whether or not ext4 should use the DIO read locking. If
593 the dioread_nolock option is specified ext4 will allocate unini‐
594 tialized extent before buffer write and convert the extent to
595 initialized after IO completes. This approach allows ext4 code
596 to avoid using inode mutex, which improves scalability on high
597 speed storages. However this does not work with data journaling
598 and dioread_nolock option will be ignored with kernel warning.
599 Note that dioread_nolock code path is only used for extent-based
600 files. Because of the restrictions this options comprises it is
601 off by default (e.g. dioread_lock).
602 max_dir_size_kb=n
604 This limits the size of the directories so that any attempt to
605 expand them beyond the specified limit in kilobytes will cause
606 an ENOSPC error. This is useful in memory-constrained environ‐
607 ments, where a very large directory can cause severe performance
608 problems or even provoke the Out Of Memory killer. (For example,
609 if there is only 512 MB memory available, a 176 MB directory may
610 seriously cramp the system's style.)
611 i_version
613 Enable 64-bit inode version support. This option is off by
614 default.
615 nombcache
617 This option disables use of mbcache for extended attribute dedu‐
618 plication. On systems where extended attributes are rarely or
619 never shared between files, use of mbcache for deduplication
620 adds unnecessary computational overhead.
621 prjquota
623 The prjquota mount option enables project quota support on the
624 filesystem. You need the quota utilities to actually enable and
625 manage the quota system. This mount option requires the project
626 filesystem feature.
627
630 The ext2, ext3, and ext4 filesystems support setting the following file
631 attributes on Linux systems using the chattr(1) utility:
632 a - append only
634 A - no atime updates
636 d - no dump
638 D - synchronous directory updates
640 i - immutable
642 S - synchronous updates
644 u - undeletable
646 In addition, the ext3 and ext4 filesystems support the following flag:
648 j - data journaling
650 Finally, the ext4 filesystem also supports the following flag:
652 e - extents format
654 For descriptions of these attribute flags, please refer to the
656 chattr(1) man page.
657
659 This section lists the file system driver (e.g., ext2, ext3, ext4) and
660 upstream kernel version where a particular file system feature was sup‐
661 ported. Note that in some cases the feature was present in earlier
662 kernel versions, but there were known, serious bugs. In other cases
663 the feature may still be considered in an experimental state. Finally,
664 note that some distributions may have backported features into older
665 kernels; in particular the kernel versions in certain "enterprise dis‐
666 tributions" can be extremely misleading.
667 filetype ext2, 2.2.0
669 sparse_super ext2, 2.2.0
671 large_file ext2, 2.2.0
673 has_journal ext3, 2.4.15
675 ext_attr ext2/ext3, 2.6.0
677 dir_index ext3, 2.6.0
679 resize_inode ext3, 2.6.10 (online resizing)
681 64bit ext4, 2.6.28
683 dir_nlink ext4, 2.6.28
685 extent ext4, 2.6.28
687 extra_isize ext4, 2.6.28
689 flex_bg ext4, 2.6.28
691 huge_file ext4, 2.6.28
693 meta_bg ext4, 2.6.28
695 uninit_bg ext4, 2.6.28
697 mmp ext4, 3.0
699 bigalloc ext4, 3.2
701 quota ext4, 3.6
703 inline_data ext4, 3.8
705 sparse_super2 ext4, 3.16
707 metadata_csum ext4, 3.18
709 encrypt ext4, 4.1
711 metadata_csum_seed ext4, 4.4
713 project ext4, 4.5
715 ea_inode ext4, 4.13
717 large_dir ext4, 4.13
719 casefold ext4, 5.2
721 verity ext4, 5.4
723
725 mke2fs(8), mke2fs.conf(5), e2fsck(8), dumpe2fs(8), tune2fs(8),
726 debugfs(8), mount(8), chattr(1)
727E2fsprogs version 1.45.6 March 2020 EXT4(5)