1TUNE2FS(8) System Manager's Manual TUNE2FS(8)
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6 tune2fs - adjust tunable filesystem parameters on ext2/ext3 filesystems
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9 tune2fs [ -l ] [ -c max-mount-counts ] [ -e errors-behavior ] [ -f ] [
10 -i interval-between-checks ] [ -j ] [ -J journal-options ] [ -m
11 reserved-blocks-percentage ] [ -o [^]mount-options[,...] ] [ -r
12 reserved-blocks-count ] [ -s sparse-super-flag ] [ -u user ] [ -g group
13 ] [ -C mount-count ] [ -L volume-name ] [ -M last-mounted-directory ] [
14 -O [^]feature[,...] ] [ -T time-last-checked ] [ -U UUID ] device
15
17 tune2fs allows the system administrator to adjust various tunable
18 filesystem parameters on Linux ext2/ext3 filesystems.
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21 -c max-mount-counts
22 Adjust the number of mounts after which the filesystem will be
23 checked by e2fsck(8). If max-mount-counts is 0 or -1, the num‐
24 ber of times the filesystem is mounted will be disregarded by
25 e2fsck(8) and the kernel.
26 Staggering the mount-counts at which filesystems are forcibly
28 checked will avoid all filesystems being checked at one time
29 when using journaled filesystems.
30 You should strongly consider the consequences of disabling
32 mount-count-dependent checking entirely. Bad disk drives,
33 cables, memory, and kernel bugs could all corrupt a filesystem
34 without marking the filesystem dirty or in error. If you are
35 using journaling on your filesystem, your filesystem will never
36 be marked dirty, so it will not normally be checked. A filesys‐
37 tem error detected by the kernel will still force an fsck on the
38 next reboot, but it may already be too late to prevent data loss
39 at that point.
40 See also the -i option for time-dependent checking.
42 -C mount-count
44 Set the number of times the filesystem has been mounted. If set
45 to a greater value than the max-mount-counts parameter set by
46 the -c option, e2fsck(8) will check the filesystem at the next
47 reboot.
48 -e error-behavior
50 Change the behavior of the kernel code when errors are detected.
51 In all cases, a filesystem error will cause e2fsck(8) to check
52 the filesystem on the next boot. error-behavior can be one of
53 the following:
54 continue Continue normal execution.
56 remount-ro Remount filesystem read-only.
58 panic Cause a kernel panic.
60 -f Force the tune2fs operation to complete even in the face of
62 errors. This option is useful when removing the has_journal
63 filesystem feature from a filesystem which has an external jour‐
64 nal (or is corrupted such that it appears to have an external
65 journal), but that external journal is not available.
66 WARNING: Removing an external journal from a filesystem which
68 was not cleanly unmounted without first replaying the external
69 journal can result in severe data loss and filesystem corrup‐
70 tion.
71 -g group
73 Set the group which can use the reserved filesystem blocks. The
74 group parameter can be a numerical gid or a group name. If a
75 group name is given, it is converted to a numerical gid before
76 it is stored in the superblock.
77 -i interval-between-checks[d|m|w]
79 Adjust the maximal time between two filesystem checks. No post‐
80 fix or d result in days, m in months, and w in weeks. A value
81 of zero will disable the time-dependent checking.
82 It is strongly recommended that either -c (mount-count-depen‐
84 dent) or -i (time-dependent) checking be enabled to force peri‐
85 odic full e2fsck(8) checking of the filesystem. Failure to do
86 so may lead to filesystem corruption (due to bad disks, cables,
87 memory, or kernel bugs) going unnoticed, ultimately resulting in
88 data loss or corruption.
89 -j Add an ext3 journal to the filesystem. If the -J option is not
91 specified, the default journal parameters will be used to create
92 an appropriately sized journal (given the size of the filesys‐
93 tem) stored within the filesystem. Note that you must be using
94 a kernel which has ext3 support in order to actually make use of
95 the journal.
96 If this option is used to create a journal on a mounted filesys‐
98 tem, an immutable file, .journal, will be created in the top-
99 level directory of the filesystem, as it is the only safe way to
100 create the journal inode while the filesystem is mounted. While
101 the ext3 journal is visible, it is not safe to delete it, or
102 modify it while the filesystem is mounted; for this reason the
103 file is marked immutable. While checking unmounted filesystems,
104 e2fsck(8) will automatically move .journal files to the invisi‐
105 ble, reserved journal inode. For all filesystems except for the
106 root filesystem, this should happen automatically and naturally
107 during the next reboot cycle. Since the root filesystem is
108 mounted read-only, e2fsck(8) must be run from a rescue floppy in
109 order to effect this transition.
110 On some distributions, such as Debian, if an initial ramdisk is
112 used, the initrd scripts will automatically convert an ext2 root
113 filesystem to ext3 if the /etc/fstab file specifies the ext3
114 filesystem for the root filesystem in order to avoid requiring
115 the use of a rescue floppy to add an ext3 journal to the root
116 filesystem.
117 -J journal-options
119 Override the default ext3 journal parameters. Journal options
120 are comma separated, and may take an argument using the equals
121 ('=') sign. The following journal options are supported:
122 size=journal-size
124 Create a journal stored in the filesystem of size
125 journal-size megabytes. The size of the journal
126 must be at least 1024 filesystem blocks (i.e., 1MB
127 if using 1k blocks, 4MB if using 4k blocks, etc.)
128 and may be no more than 102,400 filesystem blocks.
129 There must be enough free space in the filesystem to
130 create a journal of that size.
131 device=external-journal
133 Attach the filesystem to the journal block device
134 located on external-journal. The external journal
135 must have been already created using the command
136 mke2fs -O journal_dev external-journal
138 Note that external-journal must be formatted with
140 the same block size as filesystems which will be
141 using it. In addition, while there is support for
142 attaching multiple filesystems to a single external
143 journal, the Linux kernel and e2fsck(8) do not cur‐
144 rently support shared external journals yet.
145 Instead of specifying a device name directly, exter‐
147 nal-journal can also be specified by either
148 LABEL=label or UUID=UUID to locate the external
149 journal by either the volume label or UUID stored in
150 the ext2 superblock at the start of the journal.
151 Use dumpe2fs(8) to display a journal device's volume
152 label and UUID. See also the -L option of
153 tune2fs(8).
154 Only one of the size or device options can be given for a
156 filesystem.
157 -l List the contents of the filesystem superblock.
159 -L volume-label
161 Set the volume label of the filesystem. Ext2 filesystem labels
162 can be at most 16 characters long; if volume-label is longer
163 than 16 characters, tune2fs will truncate it and print a warn‐
164 ing. The volume label can be used by mount(8), fsck(8), and
165 /etc/fstab(5) (and possibly others) by specifying LABEL=vol‐
166 ume_label instead of a block special device name like /dev/hda5.
167 -m reserved-blocks-percentage
169 Set the percentage of the filesystem which may only be allocated
170 by privileged processes. Reserving some number of filesystem
171 blocks for use by privileged processes is done to avoid filesys‐
172 tem fragmentation, and to allow system daemons, such as sys‐
173 logd(8), to continue to function correctly after non-privileged
174 processes are prevented from writing to the filesystem. Nor‐
175 mally, the default percentage of reserved blocks is 5%.
176 -M last-mounted-directory
178 Set the last-mounted directory for the filesystem.
179 -o [^]mount-option[,...]
181 Set or clear the indicated default mount options in the filesys‐
182 tem. Default mount options can be overridden by mount options
183 specified either in /etc/fstab(5) or on the command line argu‐
184 ments to mount(8). Older kernels may not support this feature;
185 in particular, kernels which predate 2.4.20 will almost cer‐
186 tainly ignore the default mount options field in the superblock.
187 More than one mount option can be cleared or set by separating
189 features with commas. Mount options prefixed with a caret char‐
190 acter ('^') will be cleared in the filesystem's superblock;
191 mount options without a prefix character or prefixed with a plus
192 character ('+') will be added to the filesystem.
193 The following mount options can be set or cleared using tune2fs:
195 debug Enable debugging code for this filesystem.
197 bsdgroups
199 Emulate BSD behaviour when creating new files: they
200 will take the group-id of the directory in which
201 they were created. The standard System V behaviour
202 is the default, where newly created files take on
203 the fsgid of the current process, unless the direc‐
204 tory has the setgid bit set, in which case it takes
205 the gid from the parent directory, and also gets the
206 setgid bit set if it is a directory itself.
207 user_xattr
209 Enable user-specified extended attributes.
210 acl Enable Posix Access Control Lists.
212 uid16 Disables 32-bit UIDs and GIDs. This is for interop‐
214 erability with older kernels which only store and
215 expect 16-bit values.
216 journal_data
218 When the filesystem is mounted with journalling
219 enabled, all data (not just metadata) is committed
220 into the journal prior to being written into the
221 main filesystem.
222 journal_data_ordered
224 When the filesystem is mounted with journalling
225 enabled, all data is forced directly out to the main
226 file system prior to its metadata being committed to
227 the journal.
228 journal_data_writeback
230 When the filesystem is mounted with journalling
231 enabled, data may be written into the main filesys‐
232 tem after its metadata has been committed to the
233 journal. This may increase throughput, however, it
234 may allow old data to appear in files after a crash
235 and journal recovery.
236 -O [^]feature[,...]
238 Set or clear the indicated filesystem features (options) in the
239 filesystem. More than one filesystem feature can be cleared or
240 set by separating features with commas. Filesystem features
241 prefixed with a caret character ('^') will be cleared in the
242 filesystem's superblock; filesystem features without a prefix
243 character or prefixed with a plus character ('+') will be added
244 to the filesystem.
245 The following filesystem features can be set or cleared using
247 tune2fs:
248 dir_index
250 Use hashed b-trees to speed up lookups in large
251 directories.
252 filetype
254 Store file type information in directory entries.
255 has_journal
257 Use a journal to ensure filesystem consistency even
258 across unclean shutdowns. Setting the filesystem
259 feature is equivalent to using the -j option.
260 sparse_super
262 Limit the number of backup superblocks to save space
263 on large filesystems.
264 After setting or clearing sparse_super and filetype filesystem
266 features, e2fsck(8) must be run on the filesystem to return the
267 filesystem to a consistent state. Tune2fs will print a message
268 requesting that the system administrator run e2fsck(8) if neces‐
269 sary. After setting the dir_index feature, e2fsck -D can be run
270 to convert existing directories to the hashed B-tree format.
271 Warning: Linux kernels before 2.0.39 and many 2.1 series kernels
273 do not support the filesystems that use any of these features.
274 Enabling certain filesystem features may prevent the filesystem
275 from being mounted by kernels which do not support those fea‐
276 tures.
277 -r reserved-blocks-count
279 Set the number of reserved filesystem blocks.
280 -s [0|1]
282 Turn the sparse super feature off or on. Turning this feature
283 on saves space on really big filesystems. This is the same as
284 using the -O sparse_super option.
285 Warning: Linux kernels before 2.0.39 do not support this fea‐
287 ture. Neither do all Linux 2.1 kernels; please don't use this
288 unless you know what you're doing! You need to run e2fsck(8) on
289 the filesystem after changing this feature in order to have a
290 valid filesystem.
291 -T time-last-checked
293 Set the time the filesystem was last checked using e2fsck. This
294 can be useful in scripts which use a Logical Volume Manager to
295 make a consistent snapshot of a filesystem, and then check the
296 filesystem during off hours to make sure it hasn't been cor‐
297 rupted due to hardware problems, etc. If the filesystem was
298 clean, then this option can be used to set the last checked time
299 on the original filesystem. The format of time-last-checked is
300 the international date format, with an optional time specifier,
301 i.e. YYYYMMDD[HH[MM[SS]]]. The keyword now is also accepted,
302 in which case the last checked time will be set to the current
303 time.
304 -u user
306 Set the user who can use the reserved filesystem blocks. user
307 can be a numerical uid or a user name. If a user name is given,
308 it is converted to a numerical uid before it is stored in the
309 superblock.
310 -U UUID
312 Set the universally unique identifier (UUID) of the filesystem
313 to UUID. The format of the UUID is a series of hex digits sepa‐
314 rated by hyphens, like this:
315 "c1b9d5a2-f162-11cf-9ece-0020afc76f16". The UUID parameter may
316 also be one of the following:
317 clear clear the filesystem UUID
319 random generate a new randomly-generated UUID
321 time generate a new time-based UUID
323 The UUID may be used by mount(8), fsck(8), and /etc/fstab(5)
325 (and possibly others) by specifying UUID=uuid instead of a block
326 special device name like /dev/hda1.
327 See uuidgen(8) for more information. If the system does not
329 have a good random number generator such as /dev/random or
330 /dev/urandom, tune2fs will automatically use a time-based UUID
331 instead of a randomly-generated UUID.
332
334 We haven't found any bugs yet. That doesn't mean there aren't any...
335
337 tune2fs was written by Remy Card <Remy.Card@linux.org>. It is cur‐
338 rently being maintained by Theodore Ts'o <tytso@alum.mit.edu>. tune2fs
339 uses the ext2fs library written by Theodore Ts'o <tytso@mit.edu>. This
340 manual page was written by Christian Kuhtz <chk@data-hh.Hanse.DE>.
341 Time-dependent checking was added by Uwe Ohse <uwe@tirka.gun.de>.
342
344 tune2fs is part of the e2fsprogs package and is available from
345 http://e2fsprogs.sourceforge.net.
346
348 dumpe2fs(8), e2fsck(8), mke2fs(8)
349E2fsprogs version 1.40.2 July 2007 TUNE2FS(8)