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 filesystems
26 .I interval-between-checks
37 .I reserved-blocks-percentage
41 .RI [^]mount-options [,...]
45 .I reserved-blocks-count
73 .I last-mounted-directory
77 .RI [^] feature [,...]
90 allows the system administrator to adjust various tunable filesystem
91 parameters on Linux ext2/ext3 filesystems. The current values of these
92 options can be displayed by using the
96 program, or by using the
101 .BI \-c " max-mount-counts"
102 Adjust the number of mounts after which the filesystem will be checked by
106 is 0 or \-1, the number of times the filesystem is mounted will be disregarded
111 Staggering the mount-counts at which filesystems are forcibly
112 checked will avoid all filesystems being checked at one time
113 when using journaled filesystems.
115 You should strongly consider the consequences of disabling
116 mount-count-dependent checking entirely. Bad disk drives, cables,
117 memory, and kernel bugs could all corrupt a filesystem without
118 marking the filesystem dirty or in error. If you are using
119 journaling on your filesystem, your filesystem will
121 be marked dirty, so it will not normally be checked. A
122 filesystem error detected by the kernel will still force
123 an fsck on the next reboot, but it may already be too late
124 to prevent data loss at that point.
128 option for time-dependent checking.
130 .BI \-C " mount-count"
131 Set the number of times the filesystem has been mounted.
132 If set to a greater value than the max-mount-counts parameter
137 will check the filesystem at the next reboot.
139 .BI \-e " error-behavior"
140 Change the behavior of the kernel code when errors are detected.
141 In all cases, a filesystem error will cause
143 to check the filesystem on the next boot.
145 can be one of the following:
149 Continue normal execution.
152 Remount filesystem read-only.
155 Cause a kernel panic.
158 .BI \-E " extended-options"
159 Set extended options for the filesystem. Extended options are comma
160 separated, and may take an argument using the equals ('=') sign.
161 The following extended options are supported:
164 .BI stride= stride-size
165 Configure the filesystem for a RAID array with
167 filesystem blocks. This is the number of blocks read or written to disk
168 before moving to next disk. This mostly affects placement of filesystem
169 metadata like bitmaps at
171 time to avoid placing them on a single disk, which can hurt the performance.
172 It may also be used by block allocator.
174 .BI stripe_width= stripe-width
175 Configure the filesystem for a RAID array with
177 filesystem blocks per stripe. This is typically be stride-size * N, where
178 N is the number of data disks in the RAID (e.g. RAID 5 N+1, RAID 6 N+2).
179 This allows the block allocator to prevent read-modify-write of the
180 parity in a RAID stripe if possible when the data is written.
182 .BI hash_alg= hash-alg
183 Set the default hash algorithm used for filesystems with hashed b-tree
184 directories. Valid algorithms accepted are:
191 Set a flag in the filesystem superblock indicating that it may be
192 mounted using experimental kernel code, such as the ext4dev filesystem.
195 Clear the test_fs flag, indicating the filesystem should only be mounted
196 using production-level filesystem code.
200 Force the tune2fs operation to complete even in the face of errors. This
201 option is useful when removing the
203 filesystem feature from a filesystem which has
204 an external journal (or is corrupted
205 such that it appears to have an external journal), but that
206 external journal is not available.
209 Removing an external journal from a filesystem which was not cleanly unmounted
210 without first replaying the external journal can result in
211 severe data loss and filesystem corruption.
214 Set the group which can use the reserved filesystem blocks.
217 parameter can be a numerical gid or a group name. If a group name is given,
218 it is converted to a numerical gid before it is stored in the superblock.
220 .B \-i " \fIinterval-between-checks\fR[\fBd\fR|\fBm\fR|\fBw\fR]"
221 Adjust the maximal time between two filesystem checks.
228 in weeks. A value of zero will disable the time-dependent checking.
230 It is strongly recommended that either
232 (mount-count-dependent) or
234 (time-dependent) checking be enabled to force periodic full
236 checking of the filesystem. Failure to do so may lead to filesystem
237 corruption (due to bad disks, cables, memory, or kernel bugs) going
238 unnoticed, ultimately resulting in data loss or corruption.
241 Add an ext3 journal to the filesystem. If the
243 option is not specified, the default journal parameters will be used to create
244 an appropriately sized journal (given the size of the filesystem)
245 stored within the filesystem. Note that you must be using a kernel
246 which has ext3 support in order to actually make use of the journal.
248 If this option is used to create a journal on a mounted filesystem, an
251 will be created in the top-level directory of the filesystem, as it is
252 the only safe way to create the journal inode while the filesystem is
253 mounted. While the ext3 journal is visible, it is not safe to
254 delete it, or modify it while the filesystem is mounted; for this
255 reason the file is marked immutable.
256 While checking unmounted filesystems,
258 will automatically move
260 files to the invisible, reserved journal inode. For all filesystems
261 except for the root filesystem, this should happen automatically and
262 naturally during the next reboot cycle. Since the root filesystem is
265 must be run from a rescue floppy in order to effect this transition.
267 On some distributions, such as Debian, if an initial ramdisk is used,
268 the initrd scripts will automatically convert an ext2 root filesystem
271 file specifies the ext3 filesystem for the root filesystem in order to
272 avoid requiring the use of a rescue floppy to add an ext3 journal to
275 .BR \-J " journal-options"
276 Override the default ext3 journal parameters. Journal options are comma
277 separated, and may take an argument using the equals ('=') sign.
278 The following journal options are supported:
281 .BI size= journal-size
282 Create a journal stored in the filesystem of size
284 megabytes. The size of the journal must be at least 1024 filesystem blocks
285 (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.)
286 and may be no more than 102,400 filesystem blocks.
287 There must be enough free space in the filesystem to create a journal of
290 @JDEV@.BI device= external-journal
291 @JDEV@Attach the filesystem to the journal block device located on
292 @JDEV@.IR external-journal .
294 @JDEV@journal must have been already created using the command
296 @JDEV@.B mke2fs -O journal_dev
297 @JDEV@.I external-journal
300 @JDEV@.I external-journal
301 @JDEV@must be formatted with the same block
302 @JDEV@size as filesystems which will be using it.
303 @JDEV@In addition, while there is support for attaching
304 @JDEV@multiple filesystems to a single external journal,
305 @JDEV@the Linux kernel and
307 @JDEV@do not currently support shared external journals yet.
309 @JDEV@Instead of specifying a device name directly,
310 @JDEV@.I external-journal
311 @JDEV@can also be specified by either
312 @JDEV@.BI LABEL= label
315 @JDEV@to locate the external journal by either the volume label or UUID
316 @JDEV@stored in the ext2 superblock at the start of the journal. Use
317 @JDEV@.BR dumpe2fs (8)
318 @JDEV@to display a journal device's volume label and UUID. See also the
321 @JDEV@.BR tune2fs (8).
324 @JDEV@Only one of the
325 @JDEV@.BR size " or " device
326 @JDEV@options can be given for a filesystem.
329 List the contents of the filesystem superblock, including the current
330 values of the parameters that can be set via this program.
332 .BI \-L " volume-label"
333 Set the volume label of the filesystem.
334 Ext2 filesystem labels can be at most 16 characters long; if
336 is longer than 16 characters,
338 will truncate it and print a warning. The volume label can be used
344 (and possibly others) by specifying
345 .BI LABEL= volume_label
346 instead of a block special device name like
349 .BI \-m " reserved-blocks-percentage"
350 Set the percentage of the filesystem which may only be allocated
351 by privileged processes. Reserving some number of filesystem blocks
352 for use by privileged processes is done
353 to avoid filesystem fragmentation, and to allow system
356 to continue to function correctly after non-privileged processes are
357 prevented from writing to the filesystem. Normally, the default percentage
358 of reserved blocks is 5%.
360 .BI \-M " last-mounted-directory"
361 Set the last-mounted directory for the filesystem.
363 .BR \-o " [^]\fImount-option\fR[,...]"
364 Set or clear the indicated default mount options in the filesystem.
365 Default mount options can be overridden by mount options specified
368 or on the command line arguments to
370 Older kernels may not support this feature; in particular,
371 kernels which predate 2.4.20 will almost certainly ignore the
372 default mount options field in the superblock.
374 More than one mount option can be cleared or set by separating
375 features with commas. Mount options prefixed with a
376 caret character ('^') will be cleared in the filesystem's superblock;
377 mount options without a prefix character or prefixed with a plus
378 character ('+') will be added to the filesystem.
380 The following mount options can be set or cleared using
385 Enable debugging code for this filesystem.
388 Emulate BSD behaviour when creating new files: they will take the group-id
389 of the directory in which they were created. The standard System V behaviour
390 is the default, where newly created files take on the fsgid of the current
391 process, unless the directory has the setgid bit set, in which case it takes
392 the gid from the parent directory, and also gets the setgid bit set if it is
396 Enable user-specified extended attributes.
399 Enable Posix Access Control Lists.
402 Disables 32-bit UIDs and GIDs. This is for interoperability with
403 older kernels which only store and expect 16-bit values.
406 When the filesystem is mounted with journalling enabled, all data
407 (not just metadata) is committed into the journal prior to being written
408 into the main filesystem.
410 .B journal_data_ordered
411 When the filesystem is mounted with journalling enabled, all data is forced
412 directly out to the main file system prior to its metadata being committed
415 .B journal_data_writeback
416 When the filesystem is mounted with journalling enabled, data may be
417 written into the main filesystem after its metadata has been committed
418 to the journal. This may increase throughput, however, it may allow old
419 data to appear in files after a crash and journal recovery.
422 .BR \-O " [^]\fIfeature\fR[,...]"
423 Set or clear the indicated filesystem features (options) in the filesystem.
424 More than one filesystem feature can be cleared or set by separating
425 features with commas. Filesystem features prefixed with a
426 caret character ('^') will be cleared in the filesystem's superblock;
427 filesystem features without a prefix character or prefixed with a plus
428 character ('+') will be added to the filesystem.
430 The following filesystem features can be set or cleared using
435 Filesystem can contain files that are greater than 2GB. (Modern kernels
436 set this feature automatically when a file > 2GB is created.)
439 Use hashed b-trees to speed up lookups in large directories.
442 Store file type information in directory entries.
445 Use a journal to ensure filesystem consistency even across unclean shutdowns.
446 Setting the filesystem feature is equivalent to using the
451 Limit the number of backup superblocks to save space on large filesystems.
454 Reserve space so the block group descriptor table may grow in the
457 only supports clearing this filesystem feature.
460 Allow the kernel to initialize bitmaps and inode tables and keep a high
461 watermark for the unused inodes in a filesystem, to reduce
463 time. This first e2fsck run after enabling this feature will take the
464 full time, but subsequent e2fsck runs will take only a fraction of the
465 original time, depending on how full the file system is.
468 After setting or clearing
476 must be run on the filesystem to return the filesystem to a consistent state.
478 will print a message requesting that the system administrator run
480 if necessary. After setting the
484 can be run to convert existing directories to the hashed B-tree format.
485 Enabling certain filesystem features may prevent the filesystem from being
486 mounted by kernels which do not support those features. In particular the
490 features are only supported by the ext4 filesystem.
492 .BI \-r " reserved-blocks-count"
493 Set the number of reserved filesystem blocks.
495 .BI \-T " time-last-checked"
496 Set the time the filesystem was last checked using
498 The time is interpreted using the current (local) timezone.
499 This can be useful in scripts which use a Logical Volume Manager to make
500 a consistent snapshot of a filesystem, and then check the filesystem
501 during off hours to make sure it hasn't been corrupted due to
502 hardware problems, etc. If the filesystem was clean, then this option can
503 be used to set the last checked time on the original filesystem. The format
506 is the international date format, with an optional time specifier, i.e.
507 YYYYMMDD[HH[MM[SS]]]. The keyword
509 is also accepted, in which case the last checked time will be set to the
513 Set the user who can use the reserved filesystem blocks.
515 can be a numerical uid or a user name. If a user name is given, it
516 is converted to a numerical uid before it is stored in the superblock.
519 Set the universally unique identifier (UUID) of the filesystem to
521 The format of the UUID is a series of hex digits separated by hyphens,
523 "c1b9d5a2-f162-11cf-9ece-0020afc76f16".
526 parameter may also be one of the following:
530 clear the filesystem UUID
533 generate a new randomly-generated UUID
536 generate a new time-based UUID
539 The UUID may be used by
544 (and possibly others) by specifying
546 instead of a block special device name like
551 for more information.
552 If the system does not have a good random number generator such as
557 will automatically use a time-based UUID instead of a randomly-generated UUID.
559 We haven't found any bugs yet. That doesn't mean there aren't any...
562 was written by Remy Card <Remy.Card@linux.org>. It is currently being
563 maintained by Theodore Ts'o <tytso@alum.mit.edu>.
565 uses the ext2fs library written by Theodore Ts'o <tytso@mit.edu>.
566 This manual page was written by Christian Kuhtz <chk@data-hh.Hanse.DE>.
567 Time-dependent checking was added by Uwe Ohse <uwe@tirka.gun.de>.
570 is part of the e2fsprogs package and is available from
571 http://e2fsprogs.sourceforge.net.