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

BUGS

565       We haven't found any bugs yet.  That doesn't mean there aren't any...
566

AUTHOR

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

AVAILABILITY

575       tune2fs  is  part  of  the  e2fsprogs  package  and  is  available from
576       http://e2fsprogs.sourceforge.net.
577

SEE ALSO

579       debugfs(8), dumpe2fs(8), e2fsck(8), mke2fs(8), ext4(5)
580
581
582
583E2fsprogs version 1.44.6          March 2019                        TUNE2FS(8)
Impressum