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 it may be
243 mounted using experimental kernel code, such as the ext4dev filesystem.
246 Clear the test_fs flag, indicating the filesystem should only be mounted
247 using production-level filesystem code.
251 Force the tune2fs operation to complete even in the face of errors. This
252 option is useful when removing the
254 filesystem feature from a filesystem which has
255 an external journal (or is corrupted
256 such that it appears to have an external journal), but that
257 external journal is not available. If the filesystem appears to require
260 flag must be specified twice to proceed.
263 Removing an external journal from a filesystem which was not cleanly unmounted
264 without first replaying the external journal can result in
265 severe data loss and filesystem corruption.
268 Set the group which can use the reserved filesystem blocks.
271 parameter can be a numerical gid or a group name. If a group name is given,
272 it is converted to a numerical gid before it is stored in the superblock.
274 .B \-i " \fIinterval-between-checks\fR[\fBd\fR|\fBm\fR|\fBw\fR]"
275 Adjust the maximal time between two filesystem checks.
278 will interpret the number
279 .I interval-between-checks
284 as weeks. A value of zero will disable the time-dependent checking.
286 There are pros and cons to disabling these periodic checks; see the
289 (mount-count-dependent check) option for details.
292 Change the inode size used by the file system. This requires rewriting
293 the inode table, so it requires that the file system is checked for
294 consistency first using
296 This operation can also take a while and the file system can be
297 corrupted and data lost if it is interrupted while in the middle of
298 converting the file system.
301 Add an ext3 journal to the filesystem. If the
303 option is not specified, the default journal parameters will be used to create
304 an appropriately sized journal (given the size of the filesystem)
305 stored within the filesystem. Note that you must be using a kernel
306 which has ext3 support in order to actually make use of the journal.
308 If this option is used to create a journal on a mounted filesystem, an
311 will be created in the top-level directory of the filesystem, as it is
312 the only safe way to create the journal inode while the filesystem is
313 mounted. While the ext3 journal is visible, it is not safe to
314 delete it, or modify it while the filesystem is mounted; for this
315 reason the file is marked immutable.
316 While checking unmounted filesystems,
318 will automatically move
320 files to the invisible, reserved journal inode. For all filesystems
321 except for the root filesystem, this should happen automatically and
322 naturally during the next reboot cycle. Since the root filesystem is
325 must be run from a rescue floppy in order to effect this transition.
327 On some distributions, such as Debian, if an initial ramdisk is used,
328 the initrd scripts will automatically convert an ext2 root filesystem
331 file specifies the ext3 filesystem for the root filesystem in order to
332 avoid requiring the use of a rescue floppy to add an ext3 journal to
335 .BR \-J " journal-options"
336 Override the default ext3 journal parameters. Journal options are comma
337 separated, and may take an argument using the equals ('=') sign.
338 The following journal options are supported:
341 .BI size= journal-size
342 Create a journal stored in the filesystem of size
344 megabytes. The size of the journal must be at least 1024 filesystem blocks
345 (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.)
346 and may be no more than 10,240,000 filesystem blocks.
347 There must be enough free space in the filesystem to create a journal of
350 .BI location =journal-location
351 Specify the location of the journal. The argument
353 can either be specified as a block number, or if the number has a units
354 suffix (e.g., 'M', 'G', etc.) interpret it as the offset from the
355 beginning of the file system.
357 @JDEV@.BI device= external-journal
358 @JDEV@Attach the filesystem to the journal block device located on
359 @JDEV@.IR external-journal .
361 @JDEV@journal must have been already created using the command
363 @JDEV@.B mke2fs -O journal_dev
364 @JDEV@.I external-journal
367 @JDEV@.I external-journal
368 @JDEV@must be formatted with the same block
369 @JDEV@size as filesystems which will be using it.
370 @JDEV@In addition, while there is support for attaching
371 @JDEV@multiple filesystems to a single external journal,
372 @JDEV@the Linux kernel and
374 @JDEV@do not currently support shared external journals yet.
376 @JDEV@Instead of specifying a device name directly,
377 @JDEV@.I external-journal
378 @JDEV@can also be specified by either
379 @JDEV@.BI LABEL= label
382 @JDEV@to locate the external journal by either the volume label or UUID
383 @JDEV@stored in the ext2 superblock at the start of the journal. Use
384 @JDEV@.BR dumpe2fs (8)
385 @JDEV@to display a journal device's volume label and UUID. See also the
388 @JDEV@.BR tune2fs (8).
391 @JDEV@Only one of the
392 @JDEV@.BR size " or " device
393 @JDEV@options can be given for a filesystem.
396 List the contents of the filesystem superblock, including the current
397 values of the parameters that can be set via this program.
399 .BI \-L " volume-label"
400 Set the volume label of the filesystem.
401 Ext2 filesystem labels can be at most 16 characters long; if
403 is longer than 16 characters,
405 will truncate it and print a warning. The volume label can be used
411 (and possibly others) by specifying
412 .BI LABEL= volume-label
413 instead of a block special device name like
416 .BI \-m " reserved-blocks-percentage"
417 Set the percentage of the filesystem which may only be allocated
418 by privileged processes. Reserving some number of filesystem blocks
419 for use by privileged processes is done
420 to avoid filesystem fragmentation, and to allow system
423 to continue to function correctly after non-privileged processes are
424 prevented from writing to the filesystem. Normally, the default percentage
425 of reserved blocks is 5%.
427 .BI \-M " last-mounted-directory"
428 Set the last-mounted directory for the filesystem.
430 .BR \-o " [^]\fImount-option\fR[,...]"
431 Set or clear the indicated default mount options in the filesystem.
432 Default mount options can be overridden by mount options specified
435 or on the command line arguments to
437 Older kernels may not support this feature; in particular,
438 kernels which predate 2.4.20 will almost certainly ignore the
439 default mount options field in the superblock.
441 More than one mount option can be cleared or set by separating
442 features with commas. Mount options prefixed with a
443 caret character ('^') will be cleared in the filesystem's superblock;
444 mount options without a prefix character or prefixed with a plus
445 character ('+') will be added to the filesystem.
447 The following mount options can be set or cleared using
452 Enable debugging code for this filesystem.
455 Emulate BSD behavior when creating new files: they will take the group-id
456 of the directory in which they were created. The standard System V behavior
457 is the default, where newly created files take on the fsgid of the current
458 process, unless the directory has the setgid bit set, in which case it takes
459 the gid from the parent directory, and also gets the setgid bit set if it is
463 Enable user-specified extended attributes.
466 Enable Posix Access Control Lists.
469 Disables 32-bit UIDs and GIDs. This is for interoperability with
470 older kernels which only store and expect 16-bit values.
473 When the filesystem is mounted with journalling enabled, all data
474 (not just metadata) is committed into the journal prior to being written
475 into the main filesystem.
477 .B journal_data_ordered
478 When the filesystem is mounted with journalling enabled, all data is forced
479 directly out to the main file system prior to its metadata being committed
482 .B journal_data_writeback
483 When the filesystem is mounted with journalling enabled, data may be
484 written into the main filesystem after its metadata has been committed
485 to the journal. This may increase throughput, however, it may allow old
486 data to appear in files after a crash and journal recovery.
489 The file system will be mounted with barrier operations in the journal
490 disabled. (This option is currently only supported by the ext4 file
491 system driver in 2.6.35+ kernels.)
494 The file system will be mounted with the block_validity option enabled,
495 which causes extra checks to be performed after reading or writing from
496 the file system. This prevents corrupted metadata blocks from causing
497 file system damage by overwriting parts of the inode table or block
498 group descriptors. This comes at the cost of increased memory and CPU
499 overhead, so it is enabled only for debugging purposes. (This option is
500 currently only supported by the ext4 file system driver in 2.6.35+
504 The file system will be mounted with the discard mount option. This will
505 cause the file system driver to attempt to use the trim/discard feature
506 of some storage devices (such as SSD's and thin-provisioned drives
507 available in some enterprise storage arrays) to inform the storage
508 device that blocks belonging to deleted files can be reused for other
509 purposes. (This option is currently only supported by the ext4 file
510 system driver in 2.6.35+ kernels.)
513 The file system will be mounted with the nodelalloc mount option. This
514 will disable the delayed allocation feature. (This option is currently
515 only supported by the ext4 file system driver in 2.6.35+ kernels.)
518 .BR \-O " [^]\fIfeature\fR[,...]"
519 Set or clear the indicated filesystem features (options) in the filesystem.
520 More than one filesystem feature can be cleared or set by separating
521 features with commas. Filesystem features prefixed with a
522 caret character ('^') will be cleared in the filesystem's superblock;
523 filesystem features without a prefix character or prefixed with a plus
524 character ('+') will be added to the filesystem. For a detailed
525 description of the file system features, please see the man page
528 The following filesystem features can be set or cleared using
533 Enable the file system to be larger than 2^32 blocks.
536 Use hashed b-trees to speed up lookups for large directories.
539 Allow more than 65000 subdirectories per directory.
542 Allow the value of each extended attribute to be placed in the data blocks of a
543 separate inode if necessary, increasing the limit on the size and number of
544 extended attributes per file.
546 currently only supports setting this filesystem feature.
549 Enable file system level encryption.
551 currently only supports setting this filesystem feature.
554 Enable the use of extent trees to store the location of data blocks in inodes.
556 currently only supports setting this filesystem feature.
559 Enable the extended inode fields used by ext4.
562 Store file type information in directory entries.
565 Allow bitmaps and inode tables for a block group to be placed
566 anywhere on the storage media. \fBTune2fs\fR will not reorganize
567 the location of the inode tables and allocation bitmaps, as
569 will do when it creates a freshly formatted file system with
574 Use a journal to ensure filesystem consistency even across unclean shutdowns.
575 Setting the filesystem feature is equivalent to using the
580 Increase the limit on the number of files per directory.
582 currently only supports setting this filesystem feature.
585 Support files larger than 2 terabytes in size.
588 Filesystem can contain files that are greater than 2GB.
591 Store a checksum to protect the contents in each metadata block.
593 .B metadata_csum_seed
594 Allow the filesystem to store the metadata checksum seed in the
595 superblock, enabling the administrator to change the UUID of a filesystem
598 feature while it is mounted.
601 Enable or disable multiple mount protection (MMP) feature.
604 Enable project ID tracking. This is used for project quota tracking.
607 Enable internal file system quota inodes.
610 Force the kernel to mount the file system read-only.
613 Reserve space so the block group descriptor table may grow in the
616 only supports clearing this filesystem feature.
619 Limit the number of backup superblocks to save space on large filesystems.
621 currently only supports setting this filesystem feature.
624 Allow the kernel to initialize bitmaps and inode tables lazily, and to
625 keep a high watermark for the unused inodes in a filesystem, to reduce
627 time. The first e2fsck run after enabling this feature will take the
628 full time, but subsequent e2fsck runs will take only a fraction of the
629 original time, depending on how full the file system is.
632 After setting or clearing
639 the file system may require being checked using
641 to return the filesystem to a consistent state.
643 will print a message requesting that the system administrator run
645 if necessary. After setting the
649 can be run to convert existing directories to the hashed B-tree format.
650 Enabling certain filesystem features may prevent the filesystem from being
651 mounted by kernels which do not support those features. In particular, the
655 features are only supported by the ext4 filesystem.
657 .BI \-r " reserved-blocks-count"
658 Set the number of reserved filesystem blocks.
660 .BI \-Q " quota-options"
661 Sets 'quota' feature on the superblock and works on the quota files for the
662 given quota type. Quota options could be one or more of the following:
666 Sets/clears user quota inode in the superblock.
669 Sets/clears group quota inode in the superblock.
672 Sets/clears project quota inode in the superblock.
675 .BI \-T " time-last-checked"
676 Set the time the filesystem was last checked using
678 The time is interpreted using the current (local) timezone.
679 This can be useful in scripts which use a Logical Volume Manager to make
680 a consistent snapshot of a filesystem, and then check the filesystem
681 during off hours to make sure it hasn't been corrupted due to
682 hardware problems, etc. If the filesystem was clean, then this option can
683 be used to set the last checked time on the original filesystem. The format
686 is the international date format, with an optional time specifier, i.e.
687 YYYYMMDD[HH[MM[SS]]]. The keyword
689 is also accepted, in which case the last checked time will be set to the
693 Set the user who can use the reserved filesystem blocks.
695 can be a numerical uid or a user name. If a user name is given, it
696 is converted to a numerical uid before it is stored in the superblock.
699 Set the universally unique identifier (UUID) of the filesystem to
701 The format of the UUID is a series of hex digits separated by hyphens,
703 "c1b9d5a2-f162-11cf-9ece-0020afc76f16".
706 parameter may also be one of the following:
710 clear the filesystem UUID
713 generate a new randomly-generated UUID
716 generate a new time-based UUID
719 The UUID may be used by
724 (and possibly others) by specifying
726 instead of a block special device name like
731 for more information.
732 If the system does not have a good random number generator such as
737 will automatically use a time-based UUID instead of a randomly-generated UUID.
740 Before overwriting a file system block, write the old contents of the block to
741 an undo file. This undo file can be used with e2undo(8) to restore the old
742 contents of the file system should something go wrong. If the empty string is
743 passed as the undo_file argument, the undo file will be written to a file named
744 tune2fs-\fIdevice\fR.e2undo in the directory specified via the
745 \fIE2FSPROGS_UNDO_DIR\fR environment variable.
747 WARNING: The undo file cannot be used to recover from a power or system crash.
749 We haven't found any bugs yet. That doesn't mean there aren't any...
752 was written by Remy Card <Remy.Card@linux.org>. It is currently being
753 maintained by Theodore Ts'o <tytso@alum.mit.edu>.
755 uses the ext2fs library written by Theodore Ts'o <tytso@mit.edu>.
756 This manual page was written by Christian Kuhtz <chk@data-hh.Hanse.DE>.
757 Time-dependent checking was added by Uwe Ohse <uwe@tirka.gun.de>.
760 is part of the e2fsprogs package and is available from
761 http://e2fsprogs.sourceforge.net.