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 casefold
133 This ext4 feature provides file system level character encoding
134 support for directories with the casefold (+F) flag enabled.
135 This feature is name-preserving on the disk, but it allows
136 applications to lookup for a file in the file system using an
137 encoding equivalent version of the file name.
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
263 This section describes mount options which are specific to ext2, ext3,
264 and ext4. Other generic mount options may be used as well; see
265 mount(8) for details.
266
268 The `ext2' filesystem is the standard Linux filesystem. Since Linux
269 2.5.46, for most mount options the default is determined by the
270 filesystem superblock. Set them with tune2fs(8).
271 acl|noacl
273 Support POSIX Access Control Lists (or not). See the acl(5)
274 manual page.
275 bsddf|minixdf
277 Set the behavior for the statfs system call. The minixdf behav‐
278 ior is to return in the f_blocks field the total number of
279 blocks of the filesystem, while the bsddf behavior (which is the
280 default) is to subtract the overhead blocks used by the ext2
281 filesystem and not available for file storage. Thus
282 % mount /k -o minixdf; df /k; umount /k
284 Filesystem 1024-blocks Used Available Capacity Mounted on
286 /dev/sda6 2630655 86954 2412169 3% /k
287 % mount /k -o bsddf; df /k; umount /k
289 Filesystem 1024-blocks Used Available Capacity Mounted on
291 /dev/sda6 2543714 13 2412169 0% /k
292 (Note that this example shows that one can add command line
294 options to the options given in /etc/fstab.)
295 check=none or nocheck
297 No checking is done at mount time. This is the default. This is
298 fast. It is wise to invoke e2fsck(8) every now and then, e.g.
299 at boot time. The non-default behavior is unsupported
300 (check=normal and check=strict options have been removed). Note
301 that these mount options don't have to be supported if ext4 ker‐
302 nel driver is used for ext2 and ext3 filesystems.
303 debug Print debugging info upon each (re)mount.
305 errors={continue|remount-ro|panic}
307 Define the behavior when an error is encountered. (Either
308 ignore errors and just mark the filesystem erroneous and con‐
309 tinue, or remount the filesystem read-only, or panic and halt
310 the system.) The default is set in the filesystem superblock,
311 and can be changed using tune2fs(8).
312 grpid|bsdgroups and nogrpid|sysvgroups
314 These options define what group id a newly created file gets.
315 When grpid is set, it takes the group id of the directory in
316 which it is created; otherwise (the default) it takes the fsgid
317 of the current process, unless the directory has the setgid bit
318 set, in which case it takes the gid from the parent directory,
319 and also gets the setgid bit set if it is a directory itself.
320 grpquota|noquota|quota|usrquota
322 The usrquota (same as quota) mount option enables user quota
323 support on the filesystem. grpquota enables group quotas sup‐
324 port. You need the quota utilities to actually enable and manage
325 the quota system.
326 nouid32
328 Disables 32-bit UIDs and GIDs. This is for interoperability
329 with older kernels which only store and expect 16-bit values.
330 oldalloc or orlov
332 Use old allocator or Orlov allocator for new inodes. Orlov is
333 default.
334 resgid=n and resuid=n
336 The ext2 filesystem reserves a certain percentage of the avail‐
337 able space (by default 5%, see mke2fs(8) and tune2fs(8)). These
338 options determine who can use the reserved blocks. (Roughly:
339 whoever has the specified uid, or belongs to the specified
340 group.)
341 sb=n Instead of using the normal superblock, use an alternative
343 superblock specified by n. This option is normally used when
344 the primary superblock has been corrupted. The location of
345 backup superblocks is dependent on the filesystem's blocksize,
346 the number of blocks per group, and features such as
347 sparse_super.
348 Additional backup superblocks can be determined by using the
350 mke2fs program using the -n option to print out where the
351 superblocks exist, supposing mke2fs is supplied with arguments
352 that are consistent with the filesystem's layout (e.g. block‐
353 size, blocks per group, sparse_super, etc.).
354 The block number here uses 1 k units. Thus, if you want to use
356 logical block 32768 on a filesystem with 4 k blocks, use
357 "sb=131072".
358 user_xattr|nouser_xattr
360 Support "user." extended attributes (or not).
361
365 The ext3 filesystem is a version of the ext2 filesystem which has been
366 enhanced with journaling. It supports the same options as ext2 as well
367 as the following additions:
368 journal_dev=devnum/journal_path=path
370 When the external journal device's major/minor numbers have
371 changed, these options allow the user to specify the new journal
372 location. The journal device is identified either through its
373 new major/minor numbers encoded in devnum, or via a path to the
374 device.
375 norecovery/noload
377 Don't load the journal on mounting. Note that if the filesystem
378 was not unmounted cleanly, skipping the journal replay will lead
379 to the filesystem containing inconsistencies that can lead to
380 any number of problems.
381 data={journal|ordered|writeback}
383 Specifies the journaling mode for file data. Metadata is always
384 journaled. To use modes other than ordered on the root filesys‐
385 tem, pass the mode to the kernel as boot parameter, e.g. root‐
386 flags=data=journal.
387 journal
389 All data is committed into the journal prior to being
390 written into the main filesystem.
391 ordered
393 This is the default mode. All data is forced directly
394 out to the main file system prior to its metadata being
395 committed to the journal.
396 writeback
398 Data ordering is not preserved – data may be written into
399 the main filesystem after its metadata has been committed
400 to the journal. This is rumoured to be the highest-
401 throughput option. It guarantees internal filesystem
402 integrity, however it can allow old data to appear in
403 files after a crash and journal recovery.
404 data_err=ignore
406 Just print an error message if an error occurs in a file data
407 buffer in ordered mode.
408 data_err=abort
410 Abort the journal if an error occurs in a file data buffer in
411 ordered mode.
412 barrier=0 / barrier=1
414 This disables / enables the use of write barriers in the jbd
415 code. barrier=0 disables, barrier=1 enables (default). This
416 also requires an IO stack which can support barriers, and if jbd
417 gets an error on a barrier write, it will disable barriers again
418 with a warning. Write barriers enforce proper on-disk ordering
419 of journal commits, making volatile disk write caches safe to
420 use, at some performance penalty. If your disks are battery-
421 backed in one way or another, disabling barriers may safely
422 improve performance.
423 commit=nrsec
425 Start a journal commit every nrsec seconds. The default value
426 is 5 seconds. Zero means default.
427 user_xattr
429 Enable Extended User Attributes. See the attr(5) manual page.
430 jqfmt={vfsold|vfsv0|vfsv1}
432 Apart from the old quota system (as in ext2, jqfmt=vfsold aka
433 version 1 quota) ext3 also supports journaled quotas (version 2
434 quota). jqfmt=vfsv0 or jqfmt=vfsv1 enables journaled quotas.
435 Journaled quotas have the advantage that even after a crash no
436 quota check is required. When the quota filesystem feature is
437 enabled, journaled quotas are used automatically, and this mount
438 option is ignored.
439 usrjquota=aquota.user|grpjquota=aquota.group
441 For journaled quotas (jqfmt=vfsv0 or jqfmt=vfsv1), the mount
442 options usrjquota=aquota.user and grpjquota=aquota.group are
443 required to tell the quota system which quota database files to
444 use. When the quota filesystem feature is enabled, journaled
445 quotas are used automatically, and this mount option is ignored.
446
449 The ext4 filesystem is an advanced level of the ext3 filesystem which
450 incorporates scalability and reliability enhancements for supporting
451 large filesystem.
452 The options journal_dev, journal_path, norecovery, noload, data, com‐
454 mit, orlov, oldalloc, [no]user_xattr, [no]acl, bsddf, minixdf, debug,
455 errors, data_err, grpid, bsdgroups, nogrpid, sysvgroups, resgid,
456 resuid, sb, quota, noquota, nouid32, grpquota, usrquota, usrjquota,
457 grpjquota, and jqfmt are backwardly compatible with ext3 or ext2.
458 journal_checksum | nojournal_checksum
460 The journal_checksum option enables checksumming of the journal
461 transactions. This will allow the recovery code in e2fsck and
462 the kernel to detect corruption in the kernel. It is a compati‐
463 ble change and will be ignored by older kernels.
464 journal_async_commit
466 Commit block can be written to disk without waiting for descrip‐
467 tor blocks. If enabled older kernels cannot mount the device.
468 This will enable 'journal_checksum' internally.
469 barrier=0 / barrier=1 / barrier / nobarrier
471 These mount options have the same effect as in ext3. The mount
472 options "barrier" and "nobarrier" are added for consistency with
473 other ext4 mount options.
474 The ext4 filesystem enables write barriers by default.
476 inode_readahead_blks=n
478 This tuning parameter controls the maximum number of inode table
479 blocks that ext4's inode table readahead algorithm will pre-read
480 into the buffer cache. The value must be a power of 2. The
481 default value is 32 blocks.
482 stripe=n
484 Number of filesystem blocks that mballoc will try to use for
485 allocation size and alignment. For RAID5/6 systems this should
486 be the number of data disks * RAID chunk size in filesystem
487 blocks.
488 delalloc
490 Deferring block allocation until write-out time.
491 nodelalloc
493 Disable delayed allocation. Blocks are allocated when data is
494 copied from user to page cache.
495 max_batch_time=usec
497 Maximum amount of time ext4 should wait for additional filesys‐
498 tem operations to be batch together with a synchronous write
499 operation. Since a synchronous write operation is going to force
500 a commit and then a wait for the I/O complete, it doesn't cost
501 much, and can be a huge throughput win, we wait for a small
502 amount of time to see if any other transactions can piggyback on
503 the synchronous write. The algorithm used is designed to auto‐
504 matically tune for the speed of the disk, by measuring the
505 amount of time (on average) that it takes to finish committing a
506 transaction. Call this time the "commit time". If the time that
507 the transaction has been running is less than the commit time,
508 ext4 will try sleeping for the commit time to see if other oper‐
509 ations will join the transaction. The commit time is capped by
510 the max_batch_time, which defaults to 15000 µs (15 ms). This
511 optimization can be turned off entirely by setting
512 max_batch_time to 0.
513 min_batch_time=usec
515 This parameter sets the commit time (as described above) to be
516 at least min_batch_time. It defaults to zero microseconds.
517 Increasing this parameter may improve the throughput of multi-
518 threaded, synchronous workloads on very fast disks, at the cost
519 of increasing latency.
520 journal_ioprio=prio
522 The I/O priority (from 0 to 7, where 0 is the highest priority)
523 which should be used for I/O operations submitted by kjournald2
524 during a commit operation. This defaults to 3, which is a
525 slightly higher priority than the default I/O priority.
526 abort Simulate the effects of calling ext4_abort() for debugging pur‐
528 poses. This is normally used while remounting a filesystem
529 which is already mounted.
530 auto_da_alloc|noauto_da_alloc
532 Many broken applications don't use fsync() when replacing exist‐
533 ing files via patterns such as
534 fd = open("foo.new")/write(fd,...)/close(fd)/ rename("foo.new",
536 "foo")
537 or worse yet
539 fd = open("foo", O_TRUNC)/write(fd,...)/close(fd).
541 If auto_da_alloc is enabled, ext4 will detect the replace-via-
543 rename and replace-via-truncate patterns and force that any
544 delayed allocation blocks are allocated such that at the next
545 journal commit, in the default data=ordered mode, the data
546 blocks of the new file are forced to disk before the rename()
547 operation is committed. This provides roughly the same level of
548 guarantees as ext3, and avoids the "zero-length" problem that
549 can happen when a system crashes before the delayed allocation
550 blocks are forced to disk.
551 noinit_itable
553 Do not initialize any uninitialized inode table blocks in the
554 background. This feature may be used by installation CD's so
555 that the install process can complete as quickly as possible;
556 the inode table initialization process would then be deferred
557 until the next time the filesystem is mounted.
558 init_itable=n
560 The lazy itable init code will wait n times the number of mil‐
561 liseconds it took to zero out the previous block group's inode
562 table. This minimizes the impact on system performance while the
563 filesystem's inode table is being initialized.
564 discard/nodiscard
566 Controls whether ext4 should issue discard/TRIM commands to the
567 underlying block device when blocks are freed. This is useful
568 for SSD devices and sparse/thinly-provisioned LUNs, but it is
569 off by default until sufficient testing has been done.
570 block_validity/noblock_validity
572 This option enables/disables the in-kernel facility for tracking
573 filesystem metadata blocks within internal data structures. This
574 allows multi-block allocator and other routines to quickly
575 locate extents which might overlap with filesystem metadata
576 blocks. This option is intended for debugging purposes and since
577 it negatively affects the performance, it is off by default.
578 dioread_lock/dioread_nolock
580 Controls whether or not ext4 should use the DIO read locking. If
581 the dioread_nolock option is specified ext4 will allocate unini‐
582 tialized extent before buffer write and convert the extent to
583 initialized after IO completes. This approach allows ext4 code
584 to avoid using inode mutex, which improves scalability on high
585 speed storages. However this does not work with data journaling
586 and dioread_nolock option will be ignored with kernel warning.
587 Note that dioread_nolock code path is only used for extent-based
588 files. Because of the restrictions this options comprises it is
589 off by default (e.g. dioread_lock).
590 max_dir_size_kb=n
592 This limits the size of the directories so that any attempt to
593 expand them beyond the specified limit in kilobytes will cause
594 an ENOSPC error. This is useful in memory-constrained environ‐
595 ments, where a very large directory can cause severe performance
596 problems or even provoke the Out Of Memory killer. (For example,
597 if there is only 512 MB memory available, a 176 MB directory may
598 seriously cramp the system's style.)
599 i_version
601 Enable 64-bit inode version support. This option is off by
602 default.
603 nombcache
605 This option disables use of mbcache for extended attribute dedu‐
606 plication. On systems where extended attributes are rarely or
607 never shared between files, use of mbcache for deduplication
608 adds unnecessary computational overhead.
609 prjquota
611 The prjquota mount option enables project quota support on the
612 filesystem. You need the quota utilities to actually enable and
613 manage the quota system. This mount option requires the project
614 filesystem feature.
615
618 The ext2, ext3, and ext4 filesystems support setting the following file
619 attributes on Linux systems using the chattr(1) utility:
620 a - append only
622 A - no atime updates
624 d - no dump
626 D - synchronous directory updates
628 i - immutable
630 S - synchronous updates
632 u - undeletable
634 In addition, the ext3 and ext4 filesystems support the following flag:
636 j - data journaling
638 Finally, the ext4 filesystem also supports the following flag:
640 e - extents format
642 For descriptions of these attribute flags, please refer to the
644 chattr(1) man page.
645
647 This section lists the file system driver (e.g., ext2, ext3, ext4) and
648 upstream kernel version where a particular file system feature was sup‐
649 ported. Note that in some cases the feature was present in earlier
650 kernel versions, but there were known, serious bugs. In other cases
651 the feature may still be considered in an experimental state. Finally,
652 note that some distributions may have backported features into older
653 kernels; in particular the kernel versions in certain "enterprise dis‐
654 tributions" can be extremely misleading.
655 filetype ext2, 2.2.0
657 sparse_super ext2, 2.2.0
659 large_file ext2, 2.2.0
661 has_journal ext3, 2.4.15
663 ext_attr ext2/ext3, 2.6.0
665 dir_index ext3, 2.6.0
667 resize_inode ext3, 2.6.10 (online resizing)
669 64bit ext4, 2.6.28
671 dir_nlink ext4, 2.6.28
673 extent ext4, 2.6.28
675 extra_isize ext4, 2.6.28
677 flex_bg ext4, 2.6.28
679 huge_file ext4, 2.6.28
681 meta_bg ext4, 2.6.28
683 uninit_bg ext4, 2.6.28
685 mmp ext4, 3.0
687 bigalloc ext4, 3.2
689 quota ext4, 3.6
691 inline_data ext4, 3.8
693 sparse_super2 ext4, 3.16
695 metadata_csum ext4, 3.18
697 encrypt ext4, 4.1
699 metadata_csum_seed ext4, 4.4
701 project ext4, 4.5
703 ea_inode ext4, 4.13
705 large_dir ext4, 4.13
707
709 mke2fs(8), mke2fs.conf(5), e2fsck(8), dumpe2fs(8), tune2fs(8),
710 debugfs(8), mount(8), chattr(1)
711E2fsprogs version 1.45.3 July 2019 EXT4(5)