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diff --git a/misc/ext4.5.in b/misc/ext4.5.in new file mode 100644 index 0000000..c835a34 --- /dev/null +++ b/misc/ext4.5.in @@ -0,0 +1,815 @@ +.\" -*- nroff -*- +.\" Copyright 1993, 1994, 1995 by Theodore Ts'o. All Rights Reserved. +.\" This file may be copied under the terms of the GNU Public License. +.\" +.TH EXT4 5 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@" +.SH NAME +ext2 \- the second extended file system +.br +ext3 \- the third extended file system +.br +ext4 \- the fourth extended file system +.SH DESCRIPTION +The second, third, and fourth extended file systems, or ext2, ext3, and +ext4 as they are commonly known, are Linux file systems that have +historically been the default file system for many Linux distributions. +They are general purpose file systems that have been designed for +extensibility and backwards compatibility. In particular, file systems +previously intended for use with the ext2 and ext3 file systems can be +mounted using the ext4 file system driver, and indeed in many modern +Linux distributions, the ext4 file system driver has been configured +to handle mount requests for ext2 and ext3 file systems. +.SH FILE SYSTEM FEATURES +A file system formatted for ext2, ext3, or ext4 can have some +collection of the following file system feature flags enabled. Some of +these features are not supported by all implementations of the ext2, +ext3, and ext4 file system drivers, depending on Linux kernel version in +use. On other operating systems, such as the GNU/HURD or FreeBSD, only +a very restrictive set of file system features may be supported in their +implementations of ext2. +.TP +.B 64bit +.br +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. +.TP +.B bigalloc +.br +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 +.B mke2fs \-C +option. +.IP +.B 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 +.B nodelalloc +mount option). +.IP +This feature requires that the +.B extent +feature be enabled. +.TP +.B casefold +.br +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. +.TP +.B dir_index +.br +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. +.TP +.B dir_nlink +.br +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. +.TP +.B ea_inode +.br +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. +.TP +.B encrypt +.br +Enables support for file-system level encryption of data blocks and file +names. The inode metadata (timestamps, file size, user/group ownership, +etc.) is +.I not +encrypted. +.IP +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. +.TP +.B ext_attr +.br +This feature enables the use of extended attributes. This feature is +supported by ext2, ext3, and ext4. +.TP +.B extent +.br +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 +.BR e2fsck (8) +on the file system. +(Note: both +.B extent +and +.B extents +are accepted as valid names for this feature for +historical/backwards compatibility reasons.) +.TP +.B extra_isize +.br +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. +.TP +.B filetype +.br +This feature enables the storage of file type information in directory +entries. This feature is supported by ext2, ext3, and ext4. +.TP +.B flex_bg +.br +This ext4 feature allows the per-block group metadata (allocation +bitmaps +and inode tables) +to be placed anywhere on the storage media. In addition, +.B 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 +.B \-G +option. +.TP +.B has_journal +.br +Create a journal to ensure file system consistency even across unclean +shutdowns. Setting the file system feature is equivalent to using the +.B \-j +option with +.BR mke2fs " or " tune2fs. +This feature is supported by ext3 and ext4, and ignored by the +ext2 file system driver. +.TP +.B huge_file +.br +This ext4 feature allows files to be larger than 2 terabytes in size. +.TP +.B inline_data +Allow data to be stored in the inode and extended attribute area. +.TP +.B journal_dev +.br +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. +.IP +The external journal device can be used by a file system by specifying +the +.B \-J +.BR device= <external-device> +option to +.BR mke2fs (8) +or +.BR tune2fs(8) . +.TP +.B large_dir +.br +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 +.BR dir_index ), +the maximum height of the hashed b-tree used to store the directory entries. +.TP +.B large_file +.br +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. +.TP +.B metadata_csum +.br +This ext4 feature enables metadata checksumming. This feature stores +checksums for all of the file system metadata (superblock, group +descriptor blocks, inode and block bitmaps, directories, and +extent tree blocks). The checksum algorithm used for the metadata +blocks is different than the one used for group descriptors with the +.B uninit_bg +feature. These two features are incompatible and +.B metadata_csum +will be used preferentially instead of +.BR uninit_bg . +.TP +.B metadata_csum_seed +.br +This feature allows the file system to store the metadata checksum seed in the +superblock, which allows the administrator to change the UUID of a file system +using the +.B metadata_csum +feature while it is mounted. +.TP +.B meta_bg +.br +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. +.TP +.B mmp +.br +This ext4 feature provides multiple mount protection (MMP). MMP helps to +protect the file system from being multiply mounted and is useful in +shared storage environments. +.TP +.B project +.br +This ext4 feature provides project quota support. With this feature, +the project ID of inode will be managed when the file system is mounted. +.TP +.B quota +.br +Create quota inodes (inode #3 for userquota and inode +#4 for group quota) and set them in the superblock. +With this feature, the quotas will be enabled +automatically when the file system is mounted. +.IP +Causes the quota files (i.e., user.quota and +group.quota which existed +in the older quota design) to be hidden inodes. +.TP +.B resize_inode +.br +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 +.BR resize2fs (8). +By default +.B mke2fs +will attempt to reserve enough space so that the +file system may grow to 1024 times its initial size. This can be changed +using the +.B resize +extended option. +.IP +This feature requires that the +.B sparse_super +or +.B sparse_super2 +feature be enabled. +.TP +.B sparse_super +.br +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. +.TP +.B sparse_super2 +.br +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. +.TP +.B stable_inodes +.br +Marks the file system's inode numbers and UUID as stable. +.BR resize2fs (8) +will not allow shrinking a file system with this feature, nor +will +.BR 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 +.B encrypt +feature still needs to be enabled separately. +.B stable_inodes +is a "compat" feature, so old kernels will allow it. +.TP +.B uninit_bg +.br +This ext4 file system feature indicates that the block group descriptors +will be protected using checksums, making it safe for +.BR 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 +.BR e2fsck (8), +and it also speeds up the time required for +.BR mke2fs (8) +to create the file system. +.TP +.B verity +.br +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. +.IP +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. +.SH MOUNT OPTIONS +This section describes mount options which are specific to ext2, ext3, +and ext4. Other generic mount options may be used as well; see +.BR mount (8) +for details. +.SH "Mount options for ext2" +The `ext2' file system is the standard Linux file system. +Since Linux 2.5.46, for most mount options the default +is determined by the file system superblock. Set them with +.BR tune2fs (8). +.TP +.BR acl | noacl +Support POSIX Access Control Lists (or not). See the +.BR acl (5) +manual page. +.TP +.BR bsddf | minixdf +Set the behavior for the +.I statfs +system call. The +.B minixdf +behavior is to return in the +.I f_blocks +field the total number of blocks of the file system, while the +.B bsddf +behavior (which is the default) is to subtract the overhead blocks +used by the ext2 file system and not available for file storage. Thus +.sp 1 +% mount /k \-o minixdf; df /k; umount /k +.TS +tab(#); +l2 l2 r2 l2 l2 l +l c r c c l. +File System#1024-blocks#Used#Available#Capacity#Mounted on +/dev/sda6#2630655#86954#2412169#3%#/k +.TE +.sp 1 +% mount /k \-o bsddf; df /k; umount /k +.TS +tab(#); +l2 l2 r2 l2 l2 l +l c r c c l. +File System#1024-blocks#Used#Available#Capacity#Mounted on +/dev/sda6#2543714#13#2412169#0%#/k +.TE +.sp 1 +(Note that this example shows that one can add command line options +to the options given in +.IR /etc/fstab .) +.TP +.BR check=none " or " nocheck +No checking is done at mount time. This is the default. This is fast. +It is wise to invoke +.BR e2fsck (8) +every now and then, e.g.\& at boot time. The non-default behavior is unsupported +(check=normal and check=strict options have been removed). Note that these mount options +don't have to be supported if ext4 kernel driver is used for ext2 and ext3 file systems. +.TP +.B debug +Print debugging info upon each (re)mount. +.TP +.BR errors= { continue | remount-ro | panic } +Define the behavior when an error is encountered. +(Either ignore errors and just mark the file system erroneous and continue, +or remount the file system read-only, or panic and halt the system.) +The default is set in the file system superblock, and can be +changed using +.BR tune2fs (8). +.TP +.BR grpid | bsdgroups " and " nogrpid | sysvgroups +These options define what group id a newly created file gets. +When +.B 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. +.TP +.BR grpquota | noquota | quota | usrquota +The usrquota (same as quota) mount option enables user quota support on the +file system. grpquota enables group quotas support. You need the quota utilities +to actually enable and manage the quota system. +.TP +.B nouid32 +Disables 32-bit UIDs and GIDs. This is for interoperability with older +kernels which only store and expect 16-bit values. +.TP +.BR oldalloc " or " orlov +Use old allocator or Orlov allocator for new inodes. Orlov is default. +.TP +\fBresgid=\fP\,\fIn\fP and \fBresuid=\fP\,\fIn\fP +The ext2 file system reserves a certain percentage of the available +space (by default 5%, see +.BR mke2fs (8) +and +.BR tune2fs (8)). +These options determine who can use the reserved blocks. +(Roughly: whoever has the specified uid, or belongs to the specified group.) +.TP +.BI sb= n +Instead of using the normal superblock, use an alternative superblock +specified by +.IR n . +This option is normally used when the primary superblock has been +corrupted. The location of backup superblocks is dependent on the +file system's blocksize, the number of blocks per group, and features +such as +.BR sparse_super . +.IP +Additional backup superblocks can be determined by using the +.B mke2fs +program using the +.B \-n +option to print out where the superblocks exist, supposing +.B mke2fs +is supplied with arguments that are consistent with the file system's layout +(e.g. blocksize, blocks per group, +.BR sparse_super , +etc.). +.IP +The block number here uses 1\ k units. Thus, if you want to use logical +block 32768 on a file system with 4\ k blocks, use "sb=131072". +.TP +.BR user_xattr | nouser_xattr +Support "user." extended attributes (or not). + + +.SH "Mount options for ext3" +The ext3 file system is a version of the ext2 file system which has been +enhanced with journaling. It supports the same options as ext2 as +well as the following additions: +.TP +.BR 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. +.TP +.BR norecovery / noload +Don't load the journal on mounting. Note that +if the file system was not unmounted cleanly, +skipping the journal replay will lead to the +file system containing inconsistencies that can +lead to any number of problems. +.TP +.BR data= { journal | ordered | writeback } +Specifies the journaling mode for file data. Metadata is always journaled. +To use modes other than +.B ordered +on the root file system, pass the mode to the kernel as boot parameter, e.g.\& +.IR rootflags=data=journal . +.RS +.TP +.B journal +All data is committed into the journal prior to being written into the +main file system. +.TP +.B 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. +.TP +.B writeback +Data ordering is not preserved \(en data may be written into the main +file system after its metadata has been committed to the journal. +This is rumoured to be the highest-throughput option. It guarantees +internal file system integrity, however it can allow old data to appear +in files after a crash and journal recovery. +.RE +.TP +.B data_err=ignore +Just print an error message if an error occurs in a file data buffer in +ordered mode. +.TP +.B data_err=abort +Abort the journal if an error occurs in a file data buffer in ordered mode. +.TP +.BR 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. +.TP +.BI commit= nrsec +Start a journal commit every +.I nrsec +seconds. The default value is 5 seconds. Zero means default. +.TP +.B user_xattr +Enable Extended User Attributes. See the +.BR attr (5) +manual page. +.TP +.BR 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 +.B quota +file system feature is enabled, journaled quotas are used automatically, and +this mount option is ignored. +.TP +.BR 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 +.B quota +file system feature is enabled, journaled quotas are used automatically, and +this mount option is ignored. + +.SH "Mount options for ext4" +The ext4 file system is an advanced level of the ext3 file system which +incorporates scalability and reliability enhancements for supporting large +file system. + +The options +.B journal_dev, journal_path, norecovery, noload, data, commit, orlov, +.B oldalloc, [no]user_xattr, [no]acl, bsddf, minixdf, debug, errors, +.B data_err, grpid, bsdgroups, nogrpid, sysvgroups, resgid, resuid, sb, +.B quota, noquota, nouid32, grpquota, usrquota, usrjquota, grpjquota, +.B and jqfmt are backwardly compatible with ext3 or ext2. +.TP +.B 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. +.TP +.B 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. +.TP +.BR barrier=0 " / " barrier=1 " / " barrier " / " nobarrier +These mount options have the same effect as in ext3. The mount options +"barrier" and "nobarrier" are added for consistency with other ext4 mount +options. + +The ext4 file system enables write barriers by default. +.TP +.BI 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. +.TP +.BI stripe= n +Number of file system blocks that mballoc will try to use for allocation size +and alignment. For RAID5/6 systems this should be the number of data disks * +RAID chunk size in file system blocks. +.TP +.B delalloc +Deferring block allocation until write-out time. +.TP +.B nodelalloc +Disable delayed allocation. Blocks are allocated when data is copied from user +to page cache. +.TP +.BI max_batch_time= usec +Maximum amount of time ext4 should wait for additional file system operations to +be batch together with a synchronous write operation. Since a synchronous +write operation is going to force a commit and then a wait for the I/O +complete, it doesn't cost much, and can be a huge throughput win, we wait for a +small amount of time to see if any other transactions can piggyback on the +synchronous write. The algorithm used is designed to automatically tune for +the speed of the disk, by measuring the amount of time (on average) that it +takes to finish committing a transaction. Call this time the "commit time". +If the time that the transaction has been running is less than the commit time, +ext4 will try sleeping for the commit time to see if other operations will join +the transaction. The commit time is capped by the max_batch_time, which +defaults to 15000\ \[mc]s (15\ ms). This optimization can be turned off entirely by +setting max_batch_time to 0. +.TP +.BI 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. +.TP +.BI 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. +.TP +.B abort +Simulate the effects of calling ext4_abort() for +debugging purposes. This is normally used while +remounting a file system which is already mounted. +.TP +.BR 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. +.TP +.B noinit_itable +Do not initialize any uninitialized inode table blocks in the background. This +feature may be used by installation CD's so that the install process can +complete as quickly as possible; the inode table initialization process would +then be deferred until the next time the file system is mounted. +.TP +.B init_itable=n +The lazy itable init code will wait n times the number of milliseconds it took +to zero out the previous block group's inode table. This minimizes the impact on +system performance while the file system's inode table is being initialized. +.TP +.BR 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. +.TP +.BR block_validity / noblock_validity +This option enables/disables the in-kernel facility for tracking +file system metadata blocks within internal data structures. This allows multi-\c +block allocator and other routines to quickly locate extents which might +overlap with file system metadata blocks. This option is intended for debugging +purposes and since it negatively affects the performance, it is off by default. +.TP +.BR 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). +.TP +.B 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.) +.TP +.B i_version +Enable 64-bit inode version support. This option is off by default. +.TP +.B 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. +.TP +.B prjquota +The prjquota mount option enables project quota support on the file system. +You need the quota utilities to actually enable and manage the quota system. +This mount option requires the +.B project +file system feature. + +.SH FILE ATTRIBUTES +The ext2, ext3, and ext4 file systems support setting the following file +attributes on Linux systems using the +.BR chattr (1) +utility: +.sp +.BR a " - append only" +.sp +.BR A " - no atime updates" +.sp +.BR d " - no dump" +.sp +.BR D " - synchronous directory updates" +.sp +.BR i " - immutable" +.sp +.BR S " - synchronous updates" +.sp +.BR u " - undeletable" +.sp +In addition, the ext3 and ext4 file systems support the following flag: +.sp +.BR j " - data journaling" +.sp +Finally, the ext4 file system also supports the following flag: +.sp +.BR e " - extents format" +.sp +For descriptions of these attribute flags, please refer to the +.BR chattr (1) +man page. +.SH KERNEL SUPPORT +This section lists the file system driver (e.g., ext2, ext3, ext4) and +upstream kernel version where a particular file system feature was +supported. Note that in some cases the feature was present in earlier +kernel versions, but there were known, serious bugs. In other cases the +feature may still be considered in an experimental state. Finally, note +that some distributions may have backported features into older kernels; +in particular the kernel versions in certain "enterprise distributions" +can be extremely misleading. +.IP "\fBfiletype\fR" 2in +ext2, 2.2.0 +.IP "\fBsparse_super\fR" 2in +ext2, 2.2.0 +.IP "\fBlarge_file\fR" 2in +ext2, 2.2.0 +.IP "\fBhas_journal\fR" 2in +ext3, 2.4.15 +.IP "\fBext_attr\fR" 2in +ext2/ext3, 2.6.0 +.IP "\fBdir_index\fR" 2in +ext3, 2.6.0 +.IP "\fBresize_inode\fR" 2in +ext3, 2.6.10 (online resizing) +.IP "\fB64bit\fR" 2in +ext4, 2.6.28 +.IP "\fBdir_nlink\fR" 2in +ext4, 2.6.28 +.IP "\fBextent\fR" 2in +ext4, 2.6.28 +.IP "\fBextra_isize\fR" 2in +ext4, 2.6.28 +.IP "\fBflex_bg\fR" 2in +ext4, 2.6.28 +.IP "\fBhuge_file\fR" 2in +ext4, 2.6.28 +.IP "\fBmeta_bg\fR" 2in +ext4, 2.6.28 +.IP "\fBuninit_bg\fR" 2in +ext4, 2.6.28 +.IP "\fBmmp\fR" 2in +ext4, 3.0 +.IP "\fBbigalloc\fR" 2in +ext4, 3.2 +.IP "\fBquota\fR" 2in +ext4, 3.6 +.IP "\fBinline_data\fR" 2in +ext4, 3.8 +.IP "\fBsparse_super2\fR" 2in +ext4, 3.16 +.IP "\fBmetadata_csum\fR" 2in +ext4, 3.18 +.IP "\fBencrypt\fR" 2in +ext4, 4.1 +.IP "\fBmetadata_csum_seed\fR" 2i +ext4, 4.4 +.IP "\fBproject\fR" 2i +ext4, 4.5 +.IP "\fBea_inode\fR" 2i +ext4, 4.13 +.IP "\fBlarge_dir\fR" 2i +ext4, 4.13 +.IP "\fBcasefold\fR" 2i +ext4, 5.2 +.IP "\fBverity\fR" 2i +ext4, 5.4 +.IP "\fBstable_inodes\fR" 2i +ext4, 5.5 +.SH SEE ALSO +.BR mke2fs (8), +.BR mke2fs.conf (5), +.BR e2fsck (8), +.BR dumpe2fs (8), +.BR tune2fs (8), +.BR debugfs (8), +.BR mount (8), +.BR chattr (1) |