1TUNE2FS(8)                  System Manager's Manual                 TUNE2FS(8)
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NAME

6       tune2fs  -  adjust  tunable  filesystem  parameters  on  ext2/ext3/ext4
7       filesystems
8

SYNOPSIS

10       tune2fs [ -l ] [ -c max-mount-counts ] [ -e errors-behavior ] [ -f ]  [
11       -i interval-between-checks ] [ -I new_inode_size ] [ -j ] [ -J journal-
12       options ] [ -m reserved-blocks-percentage ] [ -o [^]mount-options[,...]
13       ]  [  -r  reserved-blocks-count  ] [ -u user ] [ -g group ] [ -C mount-
14       count ] [ -E extended-options ] [ -L volume-label ] [ -M  last-mounted-
15       directory  ]  [  -O [^]feature[,...]  ] [ -Q quota-options ] [ -T time-
16       last-checked ] [ -U UUID ] [ -z undo_file ] device
17

DESCRIPTION

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
24       The  device  specifier can either be a filename (i.e., /dev/sda1), or a
25       LABEL or UUID specifier: "LABEL=volume-label" or  "UUID=uuid".   (i.e.,
26       LABEL=home or UUID=e40486c6-84d5-4f2f-b99c-032281799c9d).
27

OPTIONS

29       -c max-mount-counts
30              Adjust  the  number of mounts after which the filesystem will be
31              checked by e2fsck(8).  If max-mount-counts is 0 or -1, the  num‐
32              ber  of  times  the filesystem is mounted will be disregarded by
33              e2fsck(8) and the kernel.
34
35              Staggering the mount-counts at which  filesystems  are  forcibly
36              checked  will  avoid  all  filesystems being checked at one time
37              when using journaled filesystems.
38
39              Mount-count-dependent checking is disabled by default  to  avoid
40              unanticipated long reboots while e2fsck does its work.  However,
41              you may wish to consider the consequences  of  disabling  mount-
42              count-dependent  checking  entirely.   Bad  disk drives, cables,
43              memory, and kernel bugs could all corrupt a  filesystem  without
44              marking  the  filesystem  dirty  or  in error.  If you are using
45              journaling on your filesystem, your  filesystem  will  never  be
46              marked  dirty, so it will not normally be checked.  A filesystem
47              error detected by the kernel will still force  an  fsck  on  the
48              next reboot, but it may already be too late to prevent data loss
49              at that point.
50
51              See also the -i option for time-dependent checking.
52
53       -C mount-count
54              Set the number of times the filesystem has been mounted.  If set
55              to  a  greater  value than the max-mount-counts parameter set by
56              the -c option, e2fsck(8) will check the filesystem at  the  next
57              reboot.
58
59       -e error-behavior
60              Change the behavior of the kernel code when errors are detected.
61              In all cases, a filesystem error will cause e2fsck(8)  to  check
62              the  filesystem  on the next boot.  error-behavior can be one of
63              the following:
64
65                   continue    Continue normal execution.
66
67                   remount-ro  Remount filesystem read-only.
68
69                   panic       Cause a kernel panic.
70
71       -E extended-options
72              Set extended options for the filesystem.  Extended  options  are
73              comma separated, and may take an argument using the equals ('=')
74              sign.  The following extended options are supported:
75
76                   clear_mmp
77                          Reset the MMP block  (if  any)  back  to  the  clean
78                          state.  Use only if absolutely certain the device is
79                          not currently mounted  or  being  fscked,  or  major
80                          filesystem corruption can result.  Needs '-f'.
81
82                   mmp_update_interval=interval
83                          Adjust  the  initial MMP update interval to interval
84                          seconds.  Specifying an interval of 0 means  to  use
85                          the  default  interval.  The specified interval must
86                          be less than 300 seconds.   Requires  that  the  mmp
87                          feature be enabled.
88
89                   stride=stride-size
90                          Configure  the  filesystem  for  a  RAID  array with
91                          stride-size filesystem blocks. This is the number of
92                          blocks read or written to disk before moving to next
93                          disk. This mostly affects  placement  of  filesystem
94                          metadata  like  bitmaps  at  mke2fs(2) time to avoid
95                          placing them on a single disk, which  can  hurt  the
96                          performance.   It  may also be used by block alloca‐
97                          tor.
98
99                   stripe_width=stripe-width
100                          Configure the  filesystem  for  a  RAID  array  with
101                          stripe-width  filesystem  blocks per stripe. This is
102                          typically be stride-size * N, where N is the  number
103                          of  data  disks in the RAID (e.g. RAID 5 N+1, RAID 6
104                          N+2).  This allows the block  allocator  to  prevent
105                          read-modify-write  of the parity in a RAID stripe if
106                          possible when the data is written.
107
108                   hash_alg=hash-alg
109                          Set the default hash algorithm used for  filesystems
110                          with  hashed  b-tree  directories.  Valid algorithms
111                          accepted are: legacy, half_md4, and tea.
112
113                   mount_opts=mount_option_string
114                          Set a set of default mount  options  which  will  be
115                          used  when  the  file system is mounted.  Unlike the
116                          bitmask-based default mount  options  which  can  be
117                          specified with the -o option, mount_option_string is
118                          an arbitrary string with  a  maximum  length  of  63
119                          bytes, which is stored in the superblock.
120
121                          The  ext4  file  system  driver will first apply the
122                          bitmask-based default options, and  then  parse  the
123                          mount_option_string,   before   parsing   the  mount
124                          options passed from the mount(8) program.
125
126                          This superblock setting is only honored  in  2.6.35+
127                          kernels;  and  not  at all by the ext2 and ext3 file
128                          system drivers.
129
130                   force_fsck
131                          Set a flag in the filesystem  superblock  indicating
132                          that  errors  have been found.  This will force fsck
133                          to run at the next mount.
134
135                   test_fs
136                          Set a flag in the filesystem  superblock  indicating
137                          that  it  may  be  mounted using experimental kernel
138                          code, such as the ext4dev filesystem.
139
140                   ^test_fs
141                          Clear the test_fs flag,  indicating  the  filesystem
142                          should   only   be  mounted  using  production-level
143                          filesystem code.
144
145       -f     Force the tune2fs operation to complete  even  in  the  face  of
146              errors.   This  option  is  useful when removing the has_journal
147              filesystem feature from a filesystem which has an external jour‐
148              nal  (or  is  corrupted such that it appears to have an external
149              journal), but that external journal is not available.    If  the
150              filesystem  appears  to require journal replay, the -f flag must
151              be specified twice to proceed.
152
153              WARNING: Removing an external journal from  a  filesystem  which
154              was  not  cleanly unmounted without first replaying the external
155              journal can result in severe data loss  and  filesystem  corrup‐
156              tion.
157
158       -g group
159              Set the group which can use the reserved filesystem blocks.  The
160              group parameter can be a numerical gid or a group  name.   If  a
161              group  name  is given, it is converted to a numerical gid before
162              it is stored in the superblock.
163
164       -i  interval-between-checks[d|m|w]
165              Adjust the maximal time between two filesystem checks.  No  suf‐
166              fix  or  d  will interpret the number interval-between-checks as
167              days, m as months, and w as weeks.  A value of zero will disable
168              the time-dependent checking.
169
170              There  are pros and cons to disabling these periodic checks; see
171              the discussion under the -c (mount-count-dependent check) option
172              for details.
173
174       -I     Change  the  inode size used by the file system.   This requires
175              rewriting the inode table, so it requires that the  file  system
176              is  checked  for consistency first using e2fsck(8).  This opera‐
177              tion can also take a while and the file system can be  corrupted
178              and  data  lost if it is interrupted while in the middle of con‐
179              verting the file system.
180
181       -j     Add an ext3 journal to the filesystem.  If the -J option is  not
182              specified, the default journal parameters will be used to create
183              an appropriately sized journal (given the size of  the  filesys‐
184              tem)  stored within the filesystem.  Note that you must be using
185              a kernel which has ext3 support in order to actually make use of
186              the journal.
187
188              If this option is used to create a journal on a mounted filesys‐
189              tem, an immutable file, .journal, will be created  in  the  top-
190              level directory of the filesystem, as it is the only safe way to
191              create the journal inode while the filesystem is mounted.  While
192              the  ext3  journal  is  visible, it is not safe to delete it, or
193              modify it while the filesystem is mounted; for this  reason  the
194              file is marked immutable.  While checking unmounted filesystems,
195              e2fsck(8) will automatically move .journal files to the  invisi‐
196              ble, reserved journal inode.  For all filesystems except for the
197              root filesystem,  this should happen automatically and naturally
198              during  the  next  reboot  cycle.   Since the root filesystem is
199              mounted read-only, e2fsck(8) must be run from a rescue floppy in
200              order to effect this transition.
201
202              On  some distributions, such as Debian, if an initial ramdisk is
203              used, the initrd scripts will automatically convert an ext2 root
204              filesystem  to  ext3  if  the /etc/fstab file specifies the ext3
205              filesystem for the root filesystem in order to  avoid  requiring
206              the  use  of  a rescue floppy to add an ext3 journal to the root
207              filesystem.
208
209       -J journal-options
210              Override the default ext3 journal  parameters.  Journal  options
211              are  comma  separated, and may take an argument using the equals
212              ('=')  sign.  The following journal options are supported:
213
214                   size=journal-size
215                          Create a journal stored in the  filesystem  of  size
216                          journal-size  megabytes.    The  size of the journal
217                          must be at least 1024 filesystem blocks  (i.e.,  1MB
218                          if  using  1k  blocks, 4MB if using 4k blocks, etc.)
219                          and  may  be  no  more  than  10,240,000  filesystem
220                          blocks.   There  must  be  enough  free space in the
221                          filesystem to create a journal of that size.
222
223                   location=journal-location
224                          Specify the location of the journal.   The  argument
225                          journal-location  can either be specified as a block
226                          number, or if the number has a units  suffix  (e.g.,
227                          'M',  'G', etc.) interpret it as the offset from the
228                          beginning of the file system.
229
230                   device=external-journal
231                          Attach the filesystem to the  journal  block  device
232                          located  on  external-journal.  The external journal
233                          must have been already created using the command
234
235                          mke2fs -O journal_dev external-journal
236
237                          Note that external-journal must  be  formatted  with
238                          the  same  block  size  as filesystems which will be
239                          using it.  In addition, while there is  support  for
240                          attaching  multiple filesystems to a single external
241                          journal, the Linux kernel and e2fsck(8) do not  cur‐
242                          rently support shared external journals yet.
243
244                          Instead of specifying a device name directly, exter‐
245                          nal-journal  can  also  be   specified   by   either
246                          LABEL=label  or  UUID=UUID  to  locate  the external
247                          journal by either the volume label or UUID stored in
248                          the  ext2  superblock  at  the start of the journal.
249                          Use dumpe2fs(8) to display a journal device's volume
250                          label   and   UUID.   See  also  the  -L  option  of
251                          tune2fs(8).
252
253              Only one of the size or  device  options  can  be  given  for  a
254              filesystem.
255
256       -l     List  the  contents  of the filesystem superblock, including the
257              current values of the parameters that can be set via  this  pro‐
258              gram.
259
260       -L volume-label
261              Set  the volume label of the filesystem.  Ext2 filesystem labels
262              can be at most 16 characters long;  if  volume-label  is  longer
263              than  16  characters, tune2fs will truncate it and print a warn‐
264              ing.  The volume label can be used  by  mount(8),  fsck(8),  and
265              /etc/fstab(5)  (and possibly others) by specifying LABEL=volume-
266              label instead of a block special device name like /dev/hda5.
267
268       -m reserved-blocks-percentage
269              Set the percentage of the filesystem which may only be allocated
270              by  privileged  processes.   Reserving some number of filesystem
271              blocks for use by privileged processes is done to avoid filesys‐
272              tem  fragmentation,  and  to  allow system daemons, such as sys‐
273              logd(8), to continue to function correctly after  non-privileged
274              processes  are  prevented  from writing to the filesystem.  Nor‐
275              mally, the default percentage of reserved blocks is 5%.
276
277       -M last-mounted-directory
278              Set the last-mounted directory for the filesystem.
279
280       -o [^]mount-option[,...]
281              Set or clear the indicated default mount options in the filesys‐
282              tem.   Default  mount options can be overridden by mount options
283              specified either in /etc/fstab(5) or on the command  line  argu‐
284              ments  to mount(8).  Older kernels may not support this feature;
285              in particular, kernels which predate  2.4.20  will  almost  cer‐
286              tainly ignore the default mount options field in the superblock.
287
288              More  than  one mount option can be cleared or set by separating
289              features with commas.  Mount options prefixed with a caret char‐
290              acter  ('^')  will  be  cleared  in the filesystem's superblock;
291              mount options without a prefix character or prefixed with a plus
292              character ('+') will be added to the filesystem.
293
294              The following mount options can be set or cleared using tune2fs:
295
296                   debug  Enable debugging code for this filesystem.
297
298                   bsdgroups
299                          Emulate  BSD  behavior when creating new files: they
300                          will take the group-id of  the  directory  in  which
301                          they  were  created.  The standard System V behavior
302                          is the default, where newly created  files  take  on
303                          the  fsgid of the current process, unless the direc‐
304                          tory has the setgid bit set, in which case it  takes
305                          the gid from the parent directory, and also gets the
306                          setgid bit set if it is a directory itself.
307
308                   user_xattr
309                          Enable user-specified extended attributes.
310
311                   acl    Enable Posix Access Control Lists.
312
313                   uid16  Disables 32-bit UIDs and GIDs.  This is for interop‐
314                          erability  with  older  kernels which only store and
315                          expect 16-bit values.
316
317                   journal_data
318                          When the  filesystem  is  mounted  with  journalling
319                          enabled,  all  data (not just metadata) is committed
320                          into the journal prior to  being  written  into  the
321                          main filesystem.
322
323                   journal_data_ordered
324                          When  the  filesystem  is  mounted  with journalling
325                          enabled, all data is forced directly out to the main
326                          file system prior to its metadata being committed to
327                          the journal.
328
329                   journal_data_writeback
330                          When the  filesystem  is  mounted  with  journalling
331                          enabled,  data may be written into the main filesys‐
332                          tem after its metadata has  been  committed  to  the
333                          journal.   This may increase throughput, however, it
334                          may allow old data to appear in files after a  crash
335                          and journal recovery.
336
337                   nobarrier
338                          The  file system will be mounted with barrier opera‐
339                          tions in the journal disabled.  (This option is cur‐
340                          rently only supported by the ext4 file system driver
341                          in 2.6.35+ kernels.)
342
343                   block_validity
344                          The  file  system   will   be   mounted   with   the
345                          block_validity  option  enabled,  which causes extra
346                          checks to be performed after reading or writing from
347                          the  file  system.  This prevents corrupted metadata
348                          blocks from causing file system damage by  overwrit‐
349                          ing parts of the inode table or block group descrip‐
350                          tors.  This comes at the cost  of  increased  memory
351                          and  CPU  overhead, so it is enabled only for debug‐
352                          ging purposes.  (This option is currently only  sup‐
353                          ported  by  the  ext4  file system driver in 2.6.35+
354                          kernels.)
355
356                   discard
357                          The file system will be  mounted  with  the  discard
358                          mount  option.   This  will  cause  the  file system
359                          driver to attempt to use the trim/discard feature of
360                          some  storage devices (such as SSD's and thin-provi‐
361                          sioned drives available in some  enterprise  storage
362                          arrays)  to  inform  the  storage device that blocks
363                          belonging to deleted files can be reused  for  other
364                          purposes.   (This option is currently only supported
365                          by the ext4 file system driver in 2.6.35+ kernels.)
366
367                   nodelalloc
368                          The file system will be mounted with the  nodelalloc
369                          mount option.  This will disable the delayed alloca‐
370                          tion feature.  (This option is currently  only  sup‐
371                          ported  by  the  ext4  file system driver in 2.6.35+
372                          kernels.)
373
374       -O [^]feature[,...]
375              Set or clear the indicated filesystem features (options) in  the
376              filesystem.   More than one filesystem feature can be cleared or
377              set by separating features  with  commas.   Filesystem  features
378              prefixed  with  a  caret  character ('^') will be cleared in the
379              filesystem's superblock; filesystem features  without  a  prefix
380              character  or prefixed with a plus character ('+') will be added
381              to the filesystem.  For a detailed description of the file  sys‐
382              tem features, please see the man page ext4(5).
383
384              The  following  filesystem  features can be set or cleared using
385              tune2fs:
386
387                   64bit  Enable the  file  system  to  be  larger  than  2^32
388                          blocks.
389
390                   dir_index
391                          Use  hashed  b-trees  to  speed up lookups for large
392                          directories.
393
394                   dir_nlink
395                          Allow more than 65000 subdirectories per directory.
396
397                   ea_inode
398                          Allow the value of each  extended  attribute  to  be
399                          placed  in  the  data  blocks of a separate inode if
400                          necessary, increasing the limit on the size and num‐
401                          ber  of  extended attributes per file.  Tune2fs cur‐
402                          rently only supports setting  this  filesystem  fea‐
403                          ture.
404
405                   encrypt
406                          Enable  file  system level encryption.  Tune2fs cur‐
407                          rently only supports setting  this  filesystem  fea‐
408                          ture.
409
410                   extent Enable the use of extent trees to store the location
411                          of data blocks in inodes.   Tune2fs  currently  only
412                          supports setting this filesystem feature.
413
414                   extra_isize
415                          Enable the extended inode fields used by ext4.
416
417                   filetype
418                          Store file type information in directory entries.
419
420                   flex_bg
421                          Allow  bitmaps and inode tables for a block group to
422                          be placed anywhere on the  storage  media.   Tune2fs
423                          will not reorganize the location of the inode tables
424                          and allocation bitmaps, as mke2fs(8) will do when it
425                          creates a freshly formatted file system with flex_bg
426                          enabled.
427
428                   has_journal
429                          Use a journal to ensure filesystem consistency  even
430                          across  unclean  shutdowns.   Setting the filesystem
431                          feature is equivalent to using the -j option.
432
433                   large_dir
434                          Increase the limit on the number of files per direc‐
435                          tory.   Tune2fs currently only supports setting this
436                          filesystem feature.
437
438                   huge_file
439                          Support files larger than 2 terabytes in size.
440
441                   large_file
442                          Filesystem can contain files that are  greater  than
443                          2GB.
444
445                   metadata_csum
446                          Store  a  checksum  to  protect the contents in each
447                          metadata block.
448
449                   metadata_csum_seed
450                          Allow the filesystem to store the metadata  checksum
451                          seed  in  the superblock, enabling the administrator
452                          to change the UUID of a filesystem using  the  meta‐
453                          data_csum feature while it is mounted.
454
455                   mmp    Enable  or  disable  multiple mount protection (MMP)
456                          feature.
457
458                   project
459                          Enable  project  ID  tracking.   This  is  used  for
460                          project quota tracking.
461
462                   quota  Enable internal file system quota inodes.
463
464                   read-only
465                          Force the kernel to mount the file system read-only.
466
467                   resize_inode
468                          Reserve  space  so  the block group descriptor table
469                          may grow  in  the  future.   Tune2fs  only  supports
470                          clearing this filesystem feature.
471
472                   sparse_super
473                          Limit the number of backup superblocks to save space
474                          on large filesystems.  Tune2fs currently  only  sup‐
475                          ports setting this filesystem feature.
476
477                   uninit_bg
478                          Allow  the  kernel  to  initialize bitmaps and inode
479                          tables lazily, and to keep a high watermark for  the
480                          unused  inodes  in a filesystem, to reduce e2fsck(8)
481                          time.  The first e2fsck run after enabling this fea‐
482                          ture  will take the full time, but subsequent e2fsck
483                          runs will take only a fraction of the original time,
484                          depending on how full the file system is.
485
486              After  setting or clearing sparse_super, uninit_bg, filetype, or
487              resize_inode filesystem features, the file  system  may  require
488              being checked using e2fsck(8) to return the filesystem to a con‐
489              sistent state.  Tune2fs will print a message requesting that the
490              system  administrator run e2fsck(8) if necessary.  After setting
491              the dir_index feature, e2fsck -D can be run to convert  existing
492              directories  to  the  hashed  B-tree  format.   Enabling certain
493              filesystem  features  may  prevent  the  filesystem  from  being
494              mounted by kernels which do not support those features.  In par‐
495              ticular, the uninit_bg and flex_bg features are  only  supported
496              by the ext4 filesystem.
497
498       -r reserved-blocks-count
499              Set the number of reserved filesystem blocks.
500
501       -Q quota-options
502              Sets  'quota'  feature  on the superblock and works on the quota
503              files for the given quota type. Quota options could  be  one  or
504              more of the following:
505
506                   [^]usrquota
507                          Sets/clears user quota inode in the superblock.
508
509                   [^]grpquota
510                          Sets/clears group quota inode in the superblock.
511
512                   [^]prjquota
513                          Sets/clears project quota inode in the superblock.
514
515       -T time-last-checked
516              Set  the time the filesystem was last checked using e2fsck.  The
517              time is interpreted using the current  (local)  timezone.   This
518              can  be  useful in scripts which use a Logical Volume Manager to
519              make a consistent snapshot of a filesystem, and then  check  the
520              filesystem  during  off  hours  to make sure it hasn't been cor‐
521              rupted due to hardware problems, etc.   If  the  filesystem  was
522              clean, then this option can be used to set the last checked time
523              on the original filesystem.  The format of time-last-checked  is
524              the  international date format, with an optional time specifier,
525              i.e.  YYYYMMDD[HH[MM[SS]]].   The keyword now is also  accepted,
526              in  which  case the last checked time will be set to the current
527              time.
528
529       -u user
530              Set the user who can use the reserved filesystem  blocks.   user
531              can be a numerical uid or a user name.  If a user name is given,
532              it is converted to a numerical uid before it is  stored  in  the
533              superblock.
534
535       -U UUID
536              Set  the  universally unique identifier (UUID) of the filesystem
537              to UUID.  The format of the UUID is a series of hex digits sepa‐
538              rated          by          hyphens,          like          this:
539              "c1b9d5a2-f162-11cf-9ece-0020afc76f16".  The UUID parameter  may
540              also be one of the following:
541
542                   clear  clear the filesystem UUID
543
544                   random generate a new randomly-generated UUID
545
546                   time   generate a new time-based UUID
547
548              The  UUID  may  be  used by mount(8), fsck(8), and /etc/fstab(5)
549              (and possibly others) by specifying UUID=uuid instead of a block
550              special device name like /dev/hda1.
551
552              See  uuidgen(8)  for  more  information.  If the system does not
553              have a good random  number  generator  such  as  /dev/random  or
554              /dev/urandom,  tune2fs  will automatically use a time-based UUID
555              instead of a randomly-generated UUID.
556
557       -z undo_file
558              Before overwriting a file system block, write the  old  contents
559              of  the  block to an undo file.  This undo file can be used with
560              e2undo(8) to restore the old contents of the file system  should
561              something  go  wrong.   If  the  empty  string  is passed as the
562              undo_file argument, the undo file will  be  written  to  a  file
563              named  tune2fs-device.e2undo  in the directory specified via the
564              E2FSPROGS_UNDO_DIR environment variable.
565
566              WARNING: The undo file cannot be used to recover from a power or
567              system crash.
568

BUGS

570       We haven't found any bugs yet.  That doesn't mean there aren't any...
571

AUTHOR

573       tune2fs  was  written  by  Remy Card <Remy.Card@linux.org>.  It is cur‐
574       rently being maintained by Theodore Ts'o <tytso@alum.mit.edu>.  tune2fs
575       uses the ext2fs library written by Theodore Ts'o <tytso@mit.edu>.  This
576       manual page was  written  by  Christian  Kuhtz  <chk@data-hh.Hanse.DE>.
577       Time-dependent checking was added by Uwe Ohse <uwe@tirka.gun.de>.
578

AVAILABILITY

580       tune2fs  is  part  of  the  e2fsprogs  package  and  is  available from
581       http://e2fsprogs.sourceforge.net.
582

SEE ALSO

584       debugfs(8), dumpe2fs(8), e2fsck(8), mke2fs(8), ext4(5)
585
586
587
588E2fsprogs version 1.45.3           July 2019                        TUNE2FS(8)
Impressum