1 .\" Revision 1.0 93/06/3 23:00 chk
5 .TH TUNE2FS 8 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@"
7 tune2fs \- adjust tunable filesystem parameters on ext2/ext3/ext4 filesystems
26 .I interval-between-checks
41 .I reserved-blocks-percentage
45 .RI [^]mount-options [,...]
49 .I reserved-blocks-count
73 .I last-mounted-directory
77 .RI [^] feature [,...]
98 allows the system administrator to adjust various tunable filesystem
99 parameters on Linux ext2, ext3, or ext4 filesystems. The current values
100 of these options can be displayed by using the
104 program, or by using the
110 specifier can either be a filename (i.e., /dev/sda1), or a LABEL or UUID
111 specifier: "\fBLABEL=\fIvolume-label\fR" or "\fBUUID=\fIuuid\fR". (i.e.,
112 LABEL=home or UUID=e40486c6-84d5-4f2f-b99c-032281799c9d).
115 .BI \-c " max-mount-counts"
116 Adjust the number of mounts after which the filesystem will be checked by
120 is 0 or \-1, the number of times the filesystem is mounted will be disregarded
125 Staggering the mount-counts at which filesystems are forcibly
126 checked will avoid all filesystems being checked at one time
127 when using journaled filesystems.
129 Mount-count-dependent checking is disabled by default to avoid
130 unanticipated long reboots while e2fsck does its work. However,
131 you may wish to consider the consequences of disabling
132 mount-count-dependent checking entirely. Bad disk drives, cables,
133 memory, and kernel bugs could all corrupt a filesystem without
134 marking the filesystem dirty or in error. If you are using
135 journaling on your filesystem, your filesystem will
137 be marked dirty, so it will not normally be checked. A
138 filesystem error detected by the kernel will still force
139 an fsck on the next reboot, but it may already be too late
140 to prevent data loss at that point.
144 option for time-dependent checking.
146 .BI \-C " mount-count"
147 Set the number of times the filesystem has been mounted.
148 If set to a greater value than the max-mount-counts parameter
153 will check the filesystem at the next reboot.
155 .BI \-e " error-behavior"
156 Change the behavior of the kernel code when errors are detected.
157 In all cases, a filesystem error will cause
159 to check the filesystem on the next boot.
161 can be one of the following:
165 Continue normal execution.
168 Remount filesystem read-only.
171 Cause a kernel panic.
174 .BI \-E " extended-options"
175 Set extended options for the filesystem. Extended options are comma
176 separated, and may take an argument using the equals ('=') sign.
177 The following extended options are supported:
181 Reset the MMP block (if any) back to the clean state. Use only if
182 absolutely certain the device is not currently mounted or being
183 fscked, or major filesystem corruption can result. Needs '-f'.
185 .BI mmp_update_interval= interval
186 Adjust the initial MMP update interval to
188 seconds. Specifying an
190 of 0 means to use the default interval. The specified interval must
191 be less than 300 seconds. Requires that the
195 .BI stride= stride-size
196 Configure the filesystem for a RAID array with
198 filesystem blocks. This is the number of blocks read or written to disk
199 before moving to next disk. This mostly affects placement of filesystem
200 metadata like bitmaps at
202 time to avoid placing them on a single disk, which can hurt the performance.
203 It may also be used by block allocator.
205 .BI stripe_width= stripe-width
206 Configure the filesystem for a RAID array with
208 filesystem blocks per stripe. This is typically be stride-size * N, where
209 N is the number of data disks in the RAID (e.g. RAID 5 N+1, RAID 6 N+2).
210 This allows the block allocator to prevent read-modify-write of the
211 parity in a RAID stripe if possible when the data is written.
213 .BI hash_alg= hash-alg
214 Set the default hash algorithm used for filesystems with hashed b-tree
215 directories. Valid algorithms accepted are:
221 .BI mount_opts= mount_option_string
222 Set a set of default mount options which will be used when the file
223 system is mounted. Unlike the bitmask-based default mount options which
224 can be specified with the
227 .I mount_option_string
228 is an arbitrary string with a maximum length of 63 bytes, which is
229 stored in the superblock.
231 The ext4 file system driver will first apply
232 the bitmask-based default options, and then parse the
233 .IR mount_option_string ,
234 before parsing the mount options passed from the
238 This superblock setting is only honored in 2.6.35+ kernels;
239 and not at all by the ext2 and ext3 file system drivers.
242 Set a flag in the filesystem superblock indicating that errors have been found.
243 This will force fsck to run at the next mount.
246 Set a flag in the filesystem superblock indicating that it may be
247 mounted using experimental kernel code, such as the ext4dev filesystem.
250 Clear the test_fs flag, indicating the filesystem should only be mounted
251 using production-level filesystem code.
255 Force the tune2fs operation to complete even in the face of errors. This
256 option is useful when removing the
258 filesystem feature from a filesystem which has
259 an external journal (or is corrupted
260 such that it appears to have an external journal), but that
261 external journal is not available. If the filesystem appears to require
264 flag must be specified twice to proceed.
267 Removing an external journal from a filesystem which was not cleanly unmounted
268 without first replaying the external journal can result in
269 severe data loss and filesystem corruption.
272 Set the group which can use the reserved filesystem blocks.
275 parameter can be a numerical gid or a group name. If a group name is given,
276 it is converted to a numerical gid before it is stored in the superblock.
278 .B \-i " \fIinterval-between-checks\fR[\fBd\fR|\fBm\fR|\fBw\fR]"
279 Adjust the maximal time between two filesystem checks.
282 will interpret the number
283 .I interval-between-checks
288 as weeks. A value of zero will disable the time-dependent checking.
290 There are pros and cons to disabling these periodic checks; see the
293 (mount-count-dependent check) option for details.
296 Change the inode size used by the file system. This requires rewriting
297 the inode table, so it requires that the file system is checked for
298 consistency first using
300 This operation can also take a while and the file system can be
301 corrupted and data lost if it is interrupted while in the middle of
302 converting the file system. Backing up the file system before changing
303 inode size is recommended.
305 File systems with an inode size of 128 bytes do not support timestamps
306 beyond January 19, 2038. Inodes which are 256 bytes or larger will
307 support extended timestamps, project id's, and the ability to store some
308 extended attributes in the inode table for improved performance.
311 Add an ext3 journal to the filesystem. If the
313 option is not specified, the default journal parameters will be used to create
314 an appropriately sized journal (given the size of the filesystem)
315 stored within the filesystem. Note that you must be using a kernel
316 which has ext3 support in order to actually make use of the journal.
318 If this option is used to create a journal on a mounted filesystem, an
321 will be created in the top-level directory of the filesystem, as it is
322 the only safe way to create the journal inode while the filesystem is
323 mounted. While the ext3 journal is visible, it is not safe to
324 delete it, or modify it while the filesystem is mounted; for this
325 reason the file is marked immutable.
326 While checking unmounted filesystems,
328 will automatically move
330 files to the invisible, reserved journal inode. For all filesystems
331 except for the root filesystem, this should happen automatically and
332 naturally during the next reboot cycle. Since the root filesystem is
335 must be run from a rescue floppy in order to effect this transition.
337 On some distributions, such as Debian, if an initial ramdisk is used,
338 the initrd scripts will automatically convert an ext2 root filesystem
341 file specifies the ext3 filesystem for the root filesystem in order to
342 avoid requiring the use of a rescue floppy to add an ext3 journal to
345 .BR \-J " journal-options"
346 Override the default ext3 journal parameters. Journal options are comma
347 separated, and may take an argument using the equals ('=') sign.
348 The following journal options are supported:
351 .BI size= journal-size
352 Create a journal stored in the filesystem of size
354 megabytes. The size of the journal must be at least 1024 filesystem blocks
355 (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.)
356 and may be no more than 10,240,000 filesystem blocks.
357 There must be enough free space in the filesystem to create a journal of
360 .BI location =journal-location
361 Specify the location of the journal. The argument
363 can either be specified as a block number, or if the number has a units
364 suffix (e.g., 'M', 'G', etc.) interpret it as the offset from the
365 beginning of the file system.
367 @JDEV@.BI device= external-journal
368 @JDEV@Attach the filesystem to the journal block device located on
369 @JDEV@.IR external-journal .
371 @JDEV@journal must have been already created using the command
373 @JDEV@.B mke2fs -O journal_dev
374 @JDEV@.I external-journal
377 @JDEV@.I external-journal
378 @JDEV@must be formatted with the same block
379 @JDEV@size as filesystems which will be using it.
380 @JDEV@In addition, while there is support for attaching
381 @JDEV@multiple filesystems to a single external journal,
382 @JDEV@the Linux kernel and
384 @JDEV@do not currently support shared external journals yet.
386 @JDEV@Instead of specifying a device name directly,
387 @JDEV@.I external-journal
388 @JDEV@can also be specified by either
389 @JDEV@.BI LABEL= label
392 @JDEV@to locate the external journal by either the volume label or UUID
393 @JDEV@stored in the ext2 superblock at the start of the journal. Use
394 @JDEV@.BR dumpe2fs (8)
395 @JDEV@to display a journal device's volume label and UUID. See also the
398 @JDEV@.BR tune2fs (8).
401 @JDEV@Only one of the
402 @JDEV@.BR size " or " device
403 @JDEV@options can be given for a filesystem.
406 List the contents of the filesystem superblock, including the current
407 values of the parameters that can be set via this program.
409 .BI \-L " volume-label"
410 Set the volume label of the filesystem.
411 Ext2 filesystem labels can be at most 16 characters long; if
413 is longer than 16 characters,
415 will truncate it and print a warning. The volume label can be used
421 (and possibly others) by specifying
422 .BI LABEL= volume-label
423 instead of a block special device name like
426 .BI \-m " reserved-blocks-percentage"
427 Set the percentage of the filesystem which may only be allocated
428 by privileged processes. Reserving some number of filesystem blocks
429 for use by privileged processes is done
430 to avoid filesystem fragmentation, and to allow system
433 to continue to function correctly after non-privileged processes are
434 prevented from writing to the filesystem. Normally, the default percentage
435 of reserved blocks is 5%.
437 .BI \-M " last-mounted-directory"
438 Set the last-mounted directory for the filesystem.
440 .BR \-o " [^]\fImount-option\fR[,...]"
441 Set or clear the indicated default mount options in the filesystem.
442 Default mount options can be overridden by mount options specified
445 or on the command line arguments to
447 Older kernels may not support this feature; in particular,
448 kernels which predate 2.4.20 will almost certainly ignore the
449 default mount options field in the superblock.
451 More than one mount option can be cleared or set by separating
452 features with commas. Mount options prefixed with a
453 caret character ('^') will be cleared in the filesystem's superblock;
454 mount options without a prefix character or prefixed with a plus
455 character ('+') will be added to the filesystem.
457 The following mount options can be set or cleared using
462 Enable debugging code for this filesystem.
465 Emulate BSD behavior when creating new files: they will take the group-id
466 of the directory in which they were created. The standard System V behavior
467 is the default, where newly created files take on the fsgid of the current
468 process, unless the directory has the setgid bit set, in which case it takes
469 the gid from the parent directory, and also gets the setgid bit set if it is
473 Enable user-specified extended attributes.
476 Enable Posix Access Control Lists.
479 Disables 32-bit UIDs and GIDs. This is for interoperability with
480 older kernels which only store and expect 16-bit values.
483 When the filesystem is mounted with journalling enabled, all data
484 (not just metadata) is committed into the journal prior to being written
485 into the main filesystem.
487 .B journal_data_ordered
488 When the filesystem is mounted with journalling enabled, all data is forced
489 directly out to the main file system prior to its metadata being committed
492 .B journal_data_writeback
493 When the filesystem is mounted with journalling enabled, data may be
494 written into the main filesystem after its metadata has been committed
495 to the journal. This may increase throughput, however, it may allow old
496 data to appear in files after a crash and journal recovery.
499 The file system will be mounted with barrier operations in the journal
500 disabled. (This option is currently only supported by the ext4 file
501 system driver in 2.6.35+ kernels.)
504 The file system will be mounted with the block_validity option enabled,
505 which causes extra checks to be performed after reading or writing from
506 the file system. This prevents corrupted metadata blocks from causing
507 file system damage by overwriting parts of the inode table or block
508 group descriptors. This comes at the cost of increased memory and CPU
509 overhead, so it is enabled only for debugging purposes. (This option is
510 currently only supported by the ext4 file system driver in 2.6.35+
514 The file system will be mounted with the discard mount option. This will
515 cause the file system driver to attempt to use the trim/discard feature
516 of some storage devices (such as SSD's and thin-provisioned drives
517 available in some enterprise storage arrays) to inform the storage
518 device that blocks belonging to deleted files can be reused for other
519 purposes. (This option is currently only supported by the ext4 file
520 system driver in 2.6.35+ kernels.)
523 The file system will be mounted with the nodelalloc mount option. This
524 will disable the delayed allocation feature. (This option is currently
525 only supported by the ext4 file system driver in 2.6.35+ kernels.)
528 .BR \-O " [^]\fIfeature\fR[,...]"
529 Set or clear the indicated filesystem features (options) in the filesystem.
530 More than one filesystem feature can be cleared or set by separating
531 features with commas. Filesystem features prefixed with a
532 caret character ('^') will be cleared in the filesystem's superblock;
533 filesystem features without a prefix character or prefixed with a plus
534 character ('+') will be added to the filesystem. For a detailed
535 description of the file system features, please see the man page
538 The following filesystem features can be set or cleared using
543 Enable the file system to be larger than 2^32 blocks.
546 Use hashed b-trees to speed up lookups for large directories.
549 Allow more than 65000 subdirectories per directory.
552 Allow the value of each extended attribute to be placed in the data blocks of a
553 separate inode if necessary, increasing the limit on the size and number of
554 extended attributes per file.
556 currently only supports setting this filesystem feature.
559 Enable support for file system level encryption.
561 currently only supports setting this filesystem feature.
564 Enable the use of extent trees to store the location of data blocks in inodes.
566 currently only supports setting this filesystem feature.
569 Enable the extended inode fields used by ext4.
572 Store file type information in directory entries.
575 Allow bitmaps and inode tables for a block group to be placed
576 anywhere on the storage media. \fBTune2fs\fR will not reorganize
577 the location of the inode tables and allocation bitmaps, as
579 will do when it creates a freshly formatted file system with
584 Use a journal to ensure filesystem consistency even across unclean shutdowns.
585 Setting the filesystem feature is equivalent to using the
590 Increase the limit on the number of files per directory.
592 currently only supports setting this filesystem feature.
595 Support files larger than 2 terabytes in size.
598 Filesystem can contain files that are greater than 2GB.
601 Store a checksum to protect the contents in each metadata block.
603 .B metadata_csum_seed
604 Allow the filesystem to store the metadata checksum seed in the
605 superblock, enabling the administrator to change the UUID of a filesystem
608 feature while it is mounted.
611 Enable or disable multiple mount protection (MMP) feature.
614 Enable project ID tracking. This is used for project quota tracking.
617 Enable internal file system quota inodes.
620 Force the kernel to mount the file system read-only.
623 Reserve space so the block group descriptor table may grow in the
626 only supports clearing this filesystem feature.
629 Limit the number of backup superblocks to save space on large filesystems.
631 currently only supports setting this filesystem feature.
634 Allow the kernel to initialize bitmaps and inode tables lazily, and to
635 keep a high watermark for the unused inodes in a filesystem, to reduce
637 time. The first e2fsck run after enabling this feature will take the
638 full time, but subsequent e2fsck runs will take only a fraction of the
639 original time, depending on how full the file system is.
642 Enable support for verity protected files.
644 currently only supports setting this filesystem feature.
647 After setting or clearing
654 the file system may require being checked using
656 to return the filesystem to a consistent state.
658 will print a message requesting that the system administrator run
660 if necessary. After setting the
664 can be run to convert existing directories to the hashed B-tree format.
665 Enabling certain filesystem features may prevent the filesystem from being
666 mounted by kernels which do not support those features. In particular, the
670 features are only supported by the ext4 filesystem.
672 .BI \-r " reserved-blocks-count"
673 Set the number of reserved filesystem blocks.
675 .BI \-Q " quota-options"
676 Sets 'quota' feature on the superblock and works on the quota files for the
677 given quota type. Quota options could be one or more of the following:
681 Sets/clears user quota inode in the superblock.
684 Sets/clears group quota inode in the superblock.
687 Sets/clears project quota inode in the superblock.
690 .BI \-T " time-last-checked"
691 Set the time the filesystem was last checked using
693 The time is interpreted using the current (local) timezone.
694 This can be useful in scripts which use a Logical Volume Manager to make
695 a consistent snapshot of a filesystem, and then check the filesystem
696 during off hours to make sure it hasn't been corrupted due to
697 hardware problems, etc. If the filesystem was clean, then this option can
698 be used to set the last checked time on the original filesystem. The format
701 is the international date format, with an optional time specifier, i.e.
702 YYYYMMDD[HH[MM[SS]]]. The keyword
704 is also accepted, in which case the last checked time will be set to the
708 Set the user who can use the reserved filesystem blocks.
710 can be a numerical uid or a user name. If a user name is given, it
711 is converted to a numerical uid before it is stored in the superblock.
714 Set the universally unique identifier (UUID) of the filesystem to
716 The format of the UUID is a series of hex digits separated by hyphens,
718 "c1b9d5a2-f162-11cf-9ece-0020afc76f16".
721 parameter may also be one of the following:
725 clear the filesystem UUID
728 generate a new randomly-generated UUID
731 generate a new time-based UUID
734 The UUID may be used by
739 (and possibly others) by specifying
741 instead of a block special device name like
746 for more information.
747 If the system does not have a good random number generator such as
752 will automatically use a time-based UUID instead of a randomly-generated UUID.
755 Before overwriting a file system block, write the old contents of the block to
756 an undo file. This undo file can be used with e2undo(8) to restore the old
757 contents of the file system should something go wrong. If the empty string is
758 passed as the undo_file argument, the undo file will be written to a file named
759 tune2fs-\fIdevice\fR.e2undo in the directory specified via the
760 \fIE2FSPROGS_UNDO_DIR\fR environment variable.
762 WARNING: The undo file cannot be used to recover from a power or system crash.
764 We haven't found any bugs yet. That doesn't mean there aren't any...
767 was written by Remy Card <Remy.Card@linux.org>. It is currently being
768 maintained by Theodore Ts'o <tytso@alum.mit.edu>.
770 uses the ext2fs library written by Theodore Ts'o <tytso@mit.edu>.
771 This manual page was written by Christian Kuhtz <chk@data-hh.Hanse.DE>.
772 Time-dependent checking was added by Uwe Ohse <uwe@tirka.gun.de>.
775 is part of the e2fsprogs package and is available from
776 http://e2fsprogs.sourceforge.net.