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 mmp_update_interval
53 .I reserved-blocks-count
81 .I last-mounted-directory
85 .RI [^] feature [,...]
106 allows the system administrator to adjust various tunable filesystem
107 parameters on Linux ext2, ext3, or ext4 filesystems. The current values
108 of these options can be displayed by using the
112 program, or by using the
118 specifier can either be a filename (i.e., /dev/sda1), or a LABEL or UUID
119 specifier: "\fBLABEL=\fIvolume-label\fR" or "\fBUUID=\fIuuid\fR". (i.e.,
120 LABEL=home or UUID=e40486c6-84d5-4f2f-b99c-032281799c9d).
123 .BI \-c " max-mount-counts"
124 Adjust the number of mounts after which the filesystem will be checked by
128 is 0 or \-1, the number of times the filesystem is mounted will be disregarded
133 Staggering the mount-counts at which filesystems are forcibly
134 checked will avoid all filesystems being checked at one time
135 when using journaled filesystems.
137 You should strongly consider the consequences of disabling
138 mount-count-dependent checking entirely. Bad disk drives, cables,
139 memory, and kernel bugs could all corrupt a filesystem without
140 marking the filesystem dirty or in error. If you are using
141 journaling on your filesystem, your filesystem will
143 be marked dirty, so it will not normally be checked. A
144 filesystem error detected by the kernel will still force
145 an fsck on the next reboot, but it may already be too late
146 to prevent data loss at that point.
150 option for time-dependent checking.
152 .BI \-C " mount-count"
153 Set the number of times the filesystem has been mounted.
154 If set to a greater value than the max-mount-counts parameter
159 will check the filesystem at the next reboot.
161 .BI \-e " error-behavior"
162 Change the behavior of the kernel code when errors are detected.
163 In all cases, a filesystem error will cause
165 to check the filesystem on the next boot.
167 can be one of the following:
171 Continue normal execution.
174 Remount filesystem read-only.
177 Cause a kernel panic.
180 .BI \-E " extended-options"
181 Set extended options for the filesystem. Extended options are comma
182 separated, and may take an argument using the equals ('=') sign.
183 The following extended options are supported:
187 Reset the MMP block (if any) back to the clean state. Use only if
188 absolutely certain the device is not currently mounted or being
189 fscked, or major filesystem corruption can result. Needs '-f'.
191 .BI mmp_update_interval= interval
192 Adjust the initial MMP update interval to
194 seconds. Specifying an
196 of 0 means to use the default interval. The specified interval must
197 be less than 300 seconds. Requires that the
201 .BI stride= stride-size
202 Configure the filesystem for a RAID array with
204 filesystem blocks. This is the number of blocks read or written to disk
205 before moving to next disk. This mostly affects placement of filesystem
206 metadata like bitmaps at
208 time to avoid placing them on a single disk, which can hurt the performance.
209 It may also be used by block allocator.
211 .BI stripe_width= stripe-width
212 Configure the filesystem for a RAID array with
214 filesystem blocks per stripe. This is typically be stride-size * N, where
215 N is the number of data disks in the RAID (e.g. RAID 5 N+1, RAID 6 N+2).
216 This allows the block allocator to prevent read-modify-write of the
217 parity in a RAID stripe if possible when the data is written.
219 .BI hash_alg= hash-alg
220 Set the default hash algorithm used for filesystems with hashed b-tree
221 directories. Valid algorithms accepted are:
227 .BI mount_opts= mount_option_string
228 Set a set of default mount options which will be used when the file
229 system is mounted. Unlike the bitmask-based default mount options which
230 can be specified with the
233 .I mount_option_string
234 is an arbitrary string with a maximum length of 63 bytes, which is
235 stored in the superblock.
237 The ext4 file system driver will first apply
238 the bitmask-based default options, and then parse the
239 .IR mount_option_string ,
240 before parsing the mount options passed from the
244 This superblock setting is only honored in 2.6.35+ kernels;
245 and not at all by the ext2 and ext3 file system drivers.
248 Set a flag in the filesystem superblock indicating that it may be
249 mounted using experimental kernel code, such as the ext4dev filesystem.
252 Clear the test_fs flag, indicating the filesystem should only be mounted
253 using production-level filesystem code.
257 Force the tune2fs operation to complete even in the face of errors. This
258 option is useful when removing the
260 filesystem feature from a filesystem which has
261 an external journal (or is corrupted
262 such that it appears to have an external journal), but that
263 external journal is not available. If the filesystem appears to require
266 flag must be specified twice to proceed.
269 Removing an external journal from a filesystem which was not cleanly unmounted
270 without first replaying the external journal can result in
271 severe data loss and filesystem corruption.
274 Set the group which can use the reserved filesystem blocks.
277 parameter can be a numerical gid or a group name. If a group name is given,
278 it is converted to a numerical gid before it is stored in the superblock.
280 .B \-i " \fIinterval-between-checks\fR[\fBd\fR|\fBm\fR|\fBw\fR]"
281 Adjust the maximal time between two filesystem checks.
284 will interpret the number
285 .I interval-between-checks
290 as weeks. A value of zero will disable the time-dependent checking.
292 It is strongly recommended that either
294 (mount-count-dependent) or
296 (time-dependent) checking be enabled to force periodic full
298 checking of the filesystem. Failure to do so may lead to filesystem
299 corruption (due to bad disks, cables, memory, or kernel bugs) going
300 unnoticed, ultimately resulting in data loss or corruption.
303 Change the inode size used by the file system. This requires rewriting
304 the inode table, so it requires that the file system is checked for
305 consistency first using
307 This operation can also take a while and the file system can be
308 corrupted and data lost if it is interrupted while in the middle of
309 converting the file system.
312 Add an ext3 journal to the filesystem. If the
314 option is not specified, the default journal parameters will be used to create
315 an appropriately sized journal (given the size of the filesystem)
316 stored within the filesystem. Note that you must be using a kernel
317 which has ext3 support in order to actually make use of the journal.
319 If this option is used to create a journal on a mounted filesystem, an
322 will be created in the top-level directory of the filesystem, as it is
323 the only safe way to create the journal inode while the filesystem is
324 mounted. While the ext3 journal is visible, it is not safe to
325 delete it, or modify it while the filesystem is mounted; for this
326 reason the file is marked immutable.
327 While checking unmounted filesystems,
329 will automatically move
331 files to the invisible, reserved journal inode. For all filesystems
332 except for the root filesystem, this should happen automatically and
333 naturally during the next reboot cycle. Since the root filesystem is
336 must be run from a rescue floppy in order to effect this transition.
338 On some distributions, such as Debian, if an initial ramdisk is used,
339 the initrd scripts will automatically convert an ext2 root filesystem
342 file specifies the ext3 filesystem for the root filesystem in order to
343 avoid requiring the use of a rescue floppy to add an ext3 journal to
346 .BR \-J " journal-options"
347 Override the default ext3 journal parameters. Journal options are comma
348 separated, and may take an argument using the equals ('=') sign.
349 The following journal options are supported:
352 .BI size= journal-size
353 Create a journal stored in the filesystem of size
355 megabytes. The size of the journal must be at least 1024 filesystem blocks
356 (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.)
357 and may be no more than 10,240,000 filesystem blocks.
358 There must be enough free space in the filesystem to create a journal of
361 .BI location =journal-location
362 Specify the location of the journal. The argument
364 can either be specified as a block number, or if the number has a units
365 suffix (e.g., 'M', 'G', etc.) interpret it as the offset from the
366 beginning of the file system.
368 @JDEV@.BI device= external-journal
369 @JDEV@Attach the filesystem to the journal block device located on
370 @JDEV@.IR external-journal .
372 @JDEV@journal must have been already created using the command
374 @JDEV@.B mke2fs -O journal_dev
375 @JDEV@.I external-journal
378 @JDEV@.I external-journal
379 @JDEV@must be formatted with the same block
380 @JDEV@size as filesystems which will be using it.
381 @JDEV@In addition, while there is support for attaching
382 @JDEV@multiple filesystems to a single external journal,
383 @JDEV@the Linux kernel and
385 @JDEV@do not currently support shared external journals yet.
387 @JDEV@Instead of specifying a device name directly,
388 @JDEV@.I external-journal
389 @JDEV@can also be specified by either
390 @JDEV@.BI LABEL= label
393 @JDEV@to locate the external journal by either the volume label or UUID
394 @JDEV@stored in the ext2 superblock at the start of the journal. Use
395 @JDEV@.BR dumpe2fs (8)
396 @JDEV@to display a journal device's volume label and UUID. See also the
399 @JDEV@.BR tune2fs (8).
402 @JDEV@Only one of the
403 @JDEV@.BR size " or " device
404 @JDEV@options can be given for a filesystem.
407 List the contents of the filesystem superblock, including the current
408 values of the parameters that can be set via this program.
410 .BI \-L " volume-label"
411 Set the volume label of the filesystem.
412 Ext2 filesystem labels can be at most 16 characters long; if
414 is longer than 16 characters,
416 will truncate it and print a warning. The volume label can be used
422 (and possibly others) by specifying
423 .BI LABEL= volume-label
424 instead of a block special device name like
427 .BI \-m " reserved-blocks-percentage"
428 Set the percentage of the filesystem which may only be allocated
429 by privileged processes. Reserving some number of filesystem blocks
430 for use by privileged processes is done
431 to avoid filesystem fragmentation, and to allow system
434 to continue to function correctly after non-privileged processes are
435 prevented from writing to the filesystem. Normally, the default percentage
436 of reserved blocks is 5%.
438 .BI \-M " last-mounted-directory"
439 Set the last-mounted directory for the filesystem.
441 .BR \-o " [^]\fImount-option\fR[,...]"
442 Set or clear the indicated default mount options in the filesystem.
443 Default mount options can be overridden by mount options specified
446 or on the command line arguments to
448 Older kernels may not support this feature; in particular,
449 kernels which predate 2.4.20 will almost certainly ignore the
450 default mount options field in the superblock.
452 More than one mount option can be cleared or set by separating
453 features with commas. Mount options prefixed with a
454 caret character ('^') will be cleared in the filesystem's superblock;
455 mount options without a prefix character or prefixed with a plus
456 character ('+') will be added to the filesystem.
458 The following mount options can be set or cleared using
463 Enable debugging code for this filesystem.
466 Emulate BSD behavior when creating new files: they will take the group-id
467 of the directory in which they were created. The standard System V behavior
468 is the default, where newly created files take on the fsgid of the current
469 process, unless the directory has the setgid bit set, in which case it takes
470 the gid from the parent directory, and also gets the setgid bit set if it is
474 Enable user-specified extended attributes.
477 Enable Posix Access Control Lists.
480 Disables 32-bit UIDs and GIDs. This is for interoperability with
481 older kernels which only store and expect 16-bit values.
484 When the filesystem is mounted with journalling enabled, all data
485 (not just metadata) is committed into the journal prior to being written
486 into the main filesystem.
488 .B journal_data_ordered
489 When the filesystem is mounted with journalling enabled, all data is forced
490 directly out to the main file system prior to its metadata being committed
493 .B journal_data_writeback
494 When the filesystem is mounted with journalling enabled, data may be
495 written into the main filesystem after its metadata has been committed
496 to the journal. This may increase throughput, however, it may allow old
497 data to appear in files after a crash and journal recovery.
500 The file system will be mounted with barrier operations in the journal
501 disabled. (This option is currently only supported by the ext4 file
502 system driver in 2.6.35+ kernels.)
505 The file system will be mounted with the block_validity option enabled,
506 which causes extra checks to be performed after reading or writing from
507 the file system. This prevents corrupted metadata blocks from causing
508 file system damage by overwriting parts of the inode table or block
509 group descriptors. This comes at the cost of increased memory and CPU
510 overhead, so it is enabled only for debugging purposes. (This option is
511 currently only supported by the ext4 file system driver in 2.6.35+
515 The file system will be mounted with the discard mount option. This will
516 cause the file system driver to attempt to use the trim/discard feature
517 of some storage devices (such as SSD's and thin-provisioned drives
518 available in some enterprise storage arrays) to inform the storage
519 device that blocks belonging to deleted files can be reused for other
520 purposes. (This option is currently only supported by the ext4 file
521 system driver in 2.6.35+ kernels.)
524 The file system will be mounted with the nodelalloc mount option. This
525 will disable the delayed allocation feature. (This option is currently
526 only supported by the ext4 file system driver in 2.6.35+ kernels.)
529 .BR \-O " [^]\fIfeature\fR[,...]"
530 Set or clear the indicated filesystem features (options) in the filesystem.
531 More than one filesystem feature can be cleared or set by separating
532 features with commas. Filesystem features prefixed with a
533 caret character ('^') will be cleared in the filesystem's superblock;
534 filesystem features without a prefix character or prefixed with a plus
535 character ('+') will be added to the filesystem. For a detailed
536 description of the file system features, please see the man page
539 The following filesystem features can be set or cleared using
544 Use hashed b-trees to speed up lookups for large directories.
547 Allow more than 65000 subdirectories per directory.
550 Enable file system level encryption.
552 currently only supports setting this filesystem feature.
555 Enable the use of extent trees to store the location of data blocks in inodes.
557 currently only supports setting this filesystem feature.
560 Enable the extended inode fields used by ext4.
563 Store file type information in directory entries.
566 Allow bitmaps and inode tables for a block group to be placed
567 anywhere on the storage media. \fBTune2fs\fR will not reorganize
568 the location of the inode tables and allocation bitmaps, as
570 will do when it creates a freshly formatted file system with
575 Use a journal to ensure filesystem consistency even across unclean shutdowns.
576 Setting the filesystem feature is equivalent to using the
581 Support files larger than 2 terabytes in size.
584 Filesystem can contain files that are greater than 2GB.
587 Store a checksum to protect the contents in each metadata block.
590 Enable or disable multiple mount protection (MMP) feature.
593 Enable project ID tracking. This is used for project quota tracking.
596 Enable internal file system quota inodes.
599 Force the kernel to mount the file system read-only.
602 Reserve space so the block group descriptor table may grow in the
605 only supports clearing this filesystem feature.
608 Limit the number of backup superblocks to save space on large filesystems.
610 currently only supports setting this filesystem feature.
613 Allow the kernel to initialize bitmaps and inode tables lazily, and to
614 keep a high watermark for the unused inodes in a filesystem, to reduce
616 time. The first e2fsck run after enabling this feature will take the
617 full time, but subsequent e2fsck runs will take only a fraction of the
618 original time, depending on how full the file system is.
621 After setting or clearing
628 the file system may require being checked using
630 to return the filesystem to a consistent state.
632 will print a message requesting that the system administrator run
634 if necessary. After setting the
638 can be run to convert existing directories to the hashed B-tree format.
639 Enabling certain filesystem features may prevent the filesystem from being
640 mounted by kernels which do not support those features. In particular, the
644 features are only supported by the ext4 filesystem.
646 .BI \-p " mmp_check_interval"
647 Set the desired MMP check interval in seconds. It is 5 seconds by default.
649 .BI \-r " reserved-blocks-count"
650 Set the number of reserved filesystem blocks.
652 .BI \-Q " quota-options"
653 Sets 'quota' feature on the superblock and works on the quota files for the
654 given quota type. Quota options could be one or more of the following:
658 Sets/clears user quota inode in the superblock.
661 Sets/clears group quota inode in the superblock.
664 Sets/clears project quota inode in the superblock.
667 .BI \-T " time-last-checked"
668 Set the time the filesystem was last checked using
670 The time is interpreted using the current (local) timezone.
671 This can be useful in scripts which use a Logical Volume Manager to make
672 a consistent snapshot of a filesystem, and then check the filesystem
673 during off hours to make sure it hasn't been corrupted due to
674 hardware problems, etc. If the filesystem was clean, then this option can
675 be used to set the last checked time on the original filesystem. The format
678 is the international date format, with an optional time specifier, i.e.
679 YYYYMMDD[HH[MM[SS]]]. The keyword
681 is also accepted, in which case the last checked time will be set to the
685 Set the user who can use the reserved filesystem blocks.
687 can be a numerical uid or a user name. If a user name is given, it
688 is converted to a numerical uid before it is stored in the superblock.
691 Set the universally unique identifier (UUID) of the filesystem to
693 The format of the UUID is a series of hex digits separated by hyphens,
695 "c1b9d5a2-f162-11cf-9ece-0020afc76f16".
698 parameter may also be one of the following:
702 clear the filesystem UUID
705 generate a new randomly-generated UUID
708 generate a new time-based UUID
711 The UUID may be used by
716 (and possibly others) by specifying
718 instead of a block special device name like
723 for more information.
724 If the system does not have a good random number generator such as
729 will automatically use a time-based UUID instead of a randomly-generated UUID.
732 Before overwriting a file system block, write the old contents of the block to
733 an undo file. This undo file can be used with e2undo(8) to restore the old
734 contents of the file system should something go wrong. If the empty string is
735 passed as the undo_file argument, the undo file will be written to a file named
736 tune2fs-\fIdevice\fR.e2undo in the directory specified via the
737 \fIE2FSPROGS_UNDO_DIR\fR environment variable.
739 WARNING: The undo file cannot be used to recover from a power or system crash.
741 We haven't found any bugs yet. That doesn't mean there aren't any...
744 was written by Remy Card <Remy.Card@linux.org>. It is currently being
745 maintained by Theodore Ts'o <tytso@alum.mit.edu>.
747 uses the ext2fs library written by Theodore Ts'o <tytso@mit.edu>.
748 This manual page was written by Christian Kuhtz <chk@data-hh.Hanse.DE>.
749 Time-dependent checking was added by Uwe Ohse <uwe@tirka.gun.de>.
752 is part of the e2fsprogs package and is available from
753 http://e2fsprogs.sourceforge.net.