1TUNE2FS(8) System Manager's Manual TUNE2FS(8)
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6 tune2fs - adjust tunable filesystem parameters on ext2/ext3/ext4
7 filesystems
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10 tune2fs [ -l ] [ -c max-mount-counts ] [ -e errors-behavior ] [ -f ] [
11 -i interval-between-checks ] [ -j ] [ -J journal-options ] [ -m
12 reserved-blocks-percentage ] [ -o [^]mount-options[,...] ] [ -r
13 reserved-blocks-count ] [ -s sparse-super-flag ] [ -u user ] [ -g group
14 ] [ -C mount-count ] [ -E extended-options ] [ -L volume-name ] [ -M
15 last-mounted-directory ] [ -O [^]feature[,...] ] [ -T time-last-
16 checked ] [ -U UUID ] device
17
19 tune2fs allows the system administrator to adjust various tunable
20 filesystem parameters on Linux ext2, ext3, or ext4 filesystems. The
21 current values of these options can be displayed by using the -l option
22 to tune2fs(8) program, or by using the dumpe2fs(8) program.
23
25 -c max-mount-counts
26 Adjust the number of mounts after which the filesystem will be
27 checked by e2fsck(8). If max-mount-counts is 0 or -1, the num‐
28 ber of times the filesystem is mounted will be disregarded by
29 e2fsck(8) and the kernel.
30 Staggering the mount-counts at which filesystems are forcibly
32 checked will avoid all filesystems being checked at one time
33 when using journaled filesystems.
34 You should strongly consider the consequences of disabling
36 mount-count-dependent checking entirely. Bad disk drives,
37 cables, memory, and kernel bugs could all corrupt a filesystem
38 without marking the filesystem dirty or in error. If you are
39 using journaling on your filesystem, your filesystem will never
40 be marked dirty, so it will not normally be checked. A filesys‐
41 tem error detected by the kernel will still force an fsck on the
42 next reboot, but it may already be too late to prevent data loss
43 at that point.
44 See also the -i option for time-dependent checking.
46 -C mount-count
48 Set the number of times the filesystem has been mounted. If set
49 to a greater value than the max-mount-counts parameter set by
50 the -c option, e2fsck(8) will check the filesystem at the next
51 reboot.
52 -e error-behavior
54 Change the behavior of the kernel code when errors are detected.
55 In all cases, a filesystem error will cause e2fsck(8) to check
56 the filesystem on the next boot. error-behavior can be one of
57 the following:
58 continue Continue normal execution.
60 remount-ro Remount filesystem read-only.
62 panic Cause a kernel panic.
64 -E extended-options
66 Set extended options for the filesystem. Extended options are
67 comma separated, and may take an argument using the equals ('=')
68 sign. The following extended options are supported:
69 stride=stride-size
71 Configure the filesystem for a RAID array with
72 stride-size filesystem blocks. This is the number of
73 blocks read or written to disk before moving to next
74 disk. This mostly affects placement of filesystem
75 metadata like bitmaps at mke2fs(2) time to avoid
76 placing them on a single disk, which can hurt the
77 performance. It may also be used by block alloca‐
78 tor.
79 stripe_width=stripe-width
81 Configure the filesystem for a RAID array with
82 stripe-width filesystem blocks per stripe. This is
83 typically be stride-size * N, where N is the number
84 of data disks in the RAID (e.g. RAID 5 N+1, RAID 6
85 N+2). This allows the block allocator to prevent
86 read-modify-write of the parity in a RAID stripe if
87 possible when the data is written.
88 hash_alg=hash-alg
90 Set the default hash algorithm used for filesystems
91 with hashed b-tree directories. Valid algorithms
92 accepted are: legacy, half_md4, and tea.
93 test_fs
95 Set a flag in the filesystem superblock indicating
96 that it may be mounted using experimental kernel
97 code, such as the ext4dev filesystem.
98 ^test_fs
100 Clear the test_fs flag, indicating the filesystem
101 should only be mounted using production-level
102 filesystem code.
103 -f Force the tune2fs operation to complete even in the face of
105 errors. This option is useful when removing the has_journal
106 filesystem feature from a filesystem which has an external jour‐
107 nal (or is corrupted such that it appears to have an external
108 journal), but that external journal is not available.
109 WARNING: Removing an external journal from a filesystem which
111 was not cleanly unmounted without first replaying the external
112 journal can result in severe data loss and filesystem corrup‐
113 tion.
114 -g group
116 Set the group which can use the reserved filesystem blocks. The
117 group parameter can be a numerical gid or a group name. If a
118 group name is given, it is converted to a numerical gid before
119 it is stored in the superblock.
120 -i interval-between-checks[d|m|w]
122 Adjust the maximal time between two filesystem checks. No suf‐
123 fix or d will interpret the number interval-between-checks as
124 days, m as months, and w as weeks. A value of zero will disable
125 the time-dependent checking.
126 It is strongly recommended that either -c (mount-count-depen‐
128 dent) or -i (time-dependent) checking be enabled to force peri‐
129 odic full e2fsck(8) checking of the filesystem. Failure to do
130 so may lead to filesystem corruption (due to bad disks, cables,
131 memory, or kernel bugs) going unnoticed, ultimately resulting in
132 data loss or corruption.
133 -j Add an ext3 journal to the filesystem. If the -J option is not
135 specified, the default journal parameters will be used to create
136 an appropriately sized journal (given the size of the filesys‐
137 tem) stored within the filesystem. Note that you must be using
138 a kernel which has ext3 support in order to actually make use of
139 the journal.
140 If this option is used to create a journal on a mounted filesys‐
142 tem, an immutable file, .journal, will be created in the top-
143 level directory of the filesystem, as it is the only safe way to
144 create the journal inode while the filesystem is mounted. While
145 the ext3 journal is visible, it is not safe to delete it, or
146 modify it while the filesystem is mounted; for this reason the
147 file is marked immutable. While checking unmounted filesystems,
148 e2fsck(8) will automatically move .journal files to the invisi‐
149 ble, reserved journal inode. For all filesystems except for the
150 root filesystem, this should happen automatically and naturally
151 during the next reboot cycle. Since the root filesystem is
152 mounted read-only, e2fsck(8) must be run from a rescue floppy in
153 order to effect this transition.
154 On some distributions, such as Debian, if an initial ramdisk is
156 used, the initrd scripts will automatically convert an ext2 root
157 filesystem to ext3 if the /etc/fstab file specifies the ext3
158 filesystem for the root filesystem in order to avoid requiring
159 the use of a rescue floppy to add an ext3 journal to the root
160 filesystem.
161 -J journal-options
163 Override the default ext3 journal parameters. Journal options
164 are comma separated, and may take an argument using the equals
165 ('=') sign. The following journal options are supported:
166 size=journal-size
168 Create a journal stored in the filesystem of size
169 journal-size megabytes. The size of the journal
170 must be at least 1024 filesystem blocks (i.e., 1MB
171 if using 1k blocks, 4MB if using 4k blocks, etc.)
172 and may be no more than 102,400 filesystem blocks.
173 There must be enough free space in the filesystem to
174 create a journal of that size.
175 device=external-journal
177 Attach the filesystem to the journal block device
178 located on external-journal. The external journal
179 must have been already created using the command
180 mke2fs -O journal_dev external-journal
182 Note that external-journal must be formatted with
184 the same block size as filesystems which will be
185 using it. In addition, while there is support for
186 attaching multiple filesystems to a single external
187 journal, the Linux kernel and e2fsck(8) do not cur‐
188 rently support shared external journals yet.
189 Instead of specifying a device name directly, exter‐
191 nal-journal can also be specified by either
192 LABEL=label or UUID=UUID to locate the external
193 journal by either the volume label or UUID stored in
194 the ext2 superblock at the start of the journal.
195 Use dumpe2fs(8) to display a journal device's volume
196 label and UUID. See also the -L option of
197 tune2fs(8).
198 Only one of the size or device options can be given for a
200 filesystem.
201 -l List the contents of the filesystem superblock, including the
203 current values of the parameters that can be set via this pro‐
204 gram.
205 -L volume-label
207 Set the volume label of the filesystem. Ext2 filesystem labels
208 can be at most 16 characters long; if volume-label is longer
209 than 16 characters, tune2fs will truncate it and print a warn‐
210 ing. The volume label can be used by mount(8), fsck(8), and
211 /etc/fstab(5) (and possibly others) by specifying LABEL=vol‐
212 ume_label instead of a block special device name like /dev/hda5.
213 -m reserved-blocks-percentage
215 Set the percentage of the filesystem which may only be allocated
216 by privileged processes. Reserving some number of filesystem
217 blocks for use by privileged processes is done to avoid filesys‐
218 tem fragmentation, and to allow system daemons, such as sys‐
219 logd(8), to continue to function correctly after non-privileged
220 processes are prevented from writing to the filesystem. Nor‐
221 mally, the default percentage of reserved blocks is 5%.
222 -M last-mounted-directory
224 Set the last-mounted directory for the filesystem.
225 -o [^]mount-option[,...]
227 Set or clear the indicated default mount options in the filesys‐
228 tem. Default mount options can be overridden by mount options
229 specified either in /etc/fstab(5) or on the command line argu‐
230 ments to mount(8). Older kernels may not support this feature;
231 in particular, kernels which predate 2.4.20 will almost cer‐
232 tainly ignore the default mount options field in the superblock.
233 More than one mount option can be cleared or set by separating
235 features with commas. Mount options prefixed with a caret char‐
236 acter ('^') will be cleared in the filesystem's superblock;
237 mount options without a prefix character or prefixed with a plus
238 character ('+') will be added to the filesystem.
239 The following mount options can be set or cleared using tune2fs:
241 debug Enable debugging code for this filesystem.
243 bsdgroups
245 Emulate BSD behaviour when creating new files: they
246 will take the group-id of the directory in which
247 they were created. The standard System V behaviour
248 is the default, where newly created files take on
249 the fsgid of the current process, unless the direc‐
250 tory has the setgid bit set, in which case it takes
251 the gid from the parent directory, and also gets the
252 setgid bit set if it is a directory itself.
253 user_xattr
255 Enable user-specified extended attributes.
256 acl Enable Posix Access Control Lists.
258 uid16 Disables 32-bit UIDs and GIDs. This is for interop‐
260 erability with older kernels which only store and
261 expect 16-bit values.
262 journal_data
264 When the filesystem is mounted with journalling
265 enabled, all data (not just metadata) is committed
266 into the journal prior to being written into the
267 main filesystem.
268 journal_data_ordered
270 When the filesystem is mounted with journalling
271 enabled, all data is forced directly out to the main
272 file system prior to its metadata being committed to
273 the journal.
274 journal_data_writeback
276 When the filesystem is mounted with journalling
277 enabled, data may be written into the main filesys‐
278 tem after its metadata has been committed to the
279 journal. This may increase throughput, however, it
280 may allow old data to appear in files after a crash
281 and journal recovery.
282 -O [^]feature[,...]
284 Set or clear the indicated filesystem features (options) in the
285 filesystem. More than one filesystem feature can be cleared or
286 set by separating features with commas. Filesystem features
287 prefixed with a caret character ('^') will be cleared in the
288 filesystem's superblock; filesystem features without a prefix
289 character or prefixed with a plus character ('+') will be added
290 to the filesystem.
291 The following filesystem features can be set or cleared using
293 tune2fs:
294 dir_index
296 Use hashed b-trees to speed up lookups in large
297 directories.
298 filetype
300 Store file type information in directory entries.
301 flex_bg
303 Allow bitmaps and inode tables for a block group to
304 be placed anywhere on the storage media. Tune2fs
305 will not reorganize the location of the inode tables
306 and allocation bitmaps, as mke2fs(8) will do when it
307 creates a freshly formated file system with flex_bg
308 enabled.
309 has_journal
311 Use a journal to ensure filesystem consistency even
312 across unclean shutdowns. Setting the filesystem
313 feature is equivalent to using the -j option.
314 large_file
316 Filesystem can contain files that are greater than
317 2GB. (Modern kernels set this feature automatically
318 when a file > 2GB is created.)
319 resize_inode
321 Reserve space so the block group descriptor table
322 may grow in the future. Tune2fs only supports
323 clearing this filesystem feature.
324 sparse_super
326 Limit the number of backup superblocks to save space
327 on large filesystems.
328 uninit_bg
330 Allow the kernel to initialize bitmaps and inode
331 tables and keep a high watermark for the unused
332 inodes in a filesystem, to reduce e2fsck(8) time.
333 This first e2fsck run after enabling this feature
334 will take the full time, but subsequent e2fsck runs
335 will take only a fraction of the original time,
336 depending on how full the file system is.
337 After setting or clearing sparse_super, uninit_bg, filetype, or
339 resize_inode filesystem features, e2fsck(8) must be run on the
340 filesystem to return the filesystem to a consistent state.
341 Tune2fs will print a message requesting that the system adminis‐
342 trator run e2fsck(8) if necessary. After setting the dir_index
343 feature, e2fsck -D can be run to convert existing directories to
344 the hashed B-tree format. Enabling certain filesystem features
345 may prevent the filesystem from being mounted by kernels which
346 do not support those features. In particular, the uninit_bg and
347 flex_bg features are only supported by the ext4 filesystem.
348 -r reserved-blocks-count
350 Set the number of reserved filesystem blocks.
351 -T time-last-checked
353 Set the time the filesystem was last checked using e2fsck. The
354 time is interpreted using the current (local) timezone. This
355 can be useful in scripts which use a Logical Volume Manager to
356 make a consistent snapshot of a filesystem, and then check the
357 filesystem during off hours to make sure it hasn't been cor‐
358 rupted due to hardware problems, etc. If the filesystem was
359 clean, then this option can be used to set the last checked time
360 on the original filesystem. The format of time-last-checked is
361 the international date format, with an optional time specifier,
362 i.e. YYYYMMDD[HH[MM[SS]]]. The keyword now is also accepted,
363 in which case the last checked time will be set to the current
364 time.
365 -u user
367 Set the user who can use the reserved filesystem blocks. user
368 can be a numerical uid or a user name. If a user name is given,
369 it is converted to a numerical uid before it is stored in the
370 superblock.
371 -U UUID
373 Set the universally unique identifier (UUID) of the filesystem
374 to UUID. The format of the UUID is a series of hex digits sepa‐
375 rated by hyphens, like this:
376 "c1b9d5a2-f162-11cf-9ece-0020afc76f16". The UUID parameter may
377 also be one of the following:
378 clear clear the filesystem UUID
380 random generate a new randomly-generated UUID
382 time generate a new time-based UUID
384 The UUID may be used by mount(8), fsck(8), and /etc/fstab(5)
386 (and possibly others) by specifying UUID=uuid instead of a block
387 special device name like /dev/hda1.
388 See uuidgen(8) for more information. If the system does not
390 have a good random number generator such as /dev/random or
391 /dev/urandom, tune2fs will automatically use a time-based UUID
392 instead of a randomly-generated UUID.
393
395 We haven't found any bugs yet. That doesn't mean there aren't any...
396
398 tune2fs was written by Remy Card <Remy.Card@linux.org>. It is cur‐
399 rently being maintained by Theodore Ts'o <tytso@alum.mit.edu>. tune2fs
400 uses the ext2fs library written by Theodore Ts'o <tytso@mit.edu>. This
401 manual page was written by Christian Kuhtz <chk@data-hh.Hanse.DE>.
402 Time-dependent checking was added by Uwe Ohse <uwe@tirka.gun.de>.
403
405 tune2fs is part of the e2fsprogs package and is available from
406 http://e2fsprogs.sourceforge.net.
407
409 debugfs(8), dumpe2fs(8), e2fsck(8), mke2fs(8)
410E2fsprogs version 1.41.12 May 2010 TUNE2FS(8)