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tune2fs




SYNOPSIS

       tune2fs [ -l ] [ -c max-mount-counts ] [ -e  errors-behav­
       ior  ]  [  -f ] [ -i interval-between-checks ] [ -j ] [ -J
       journal-options ] [ -m reserved-blocks-percentage ]  [  -o
       [^]mount-options[,...]  ]

       [ -r reserved-blocks-count ] [ -s sparse-super-flag ] [ -u
       user ] [ -g group ] [ -C mount-count ] [ -L volume-name  ]
       [  -M  last-mounted-directory ] [ -O [^]feature[,...]  ] [
       -T time-last-checked ] [ -U UUID ] device


DESCRIPTION

       tune2fs adjusts tunable filesystem parameters on  a  Linux
       second extended filesystem.


OPTIONS

       -c max-mount-counts
              Adjust   the   maximal  mounts  count  between  two
              filesystem checks.  If max-mount-counts is  0  then
              the  number of times the filesystem is mounted will
              be disregarded by e2fsck(8) and the kernel.

              Staggering the mount-counts  at  which  filesystems
              are  forcibly  checked  will  avoid all filesystems
              being checked at  one  time  when  using  journaled
              filesystems.

              You  should  strongly  consider the consequences of
              disabling mount-count-dependent checking  entirely.
              Bad  disk  drives,  cables, memory, and kernel bugs
              could all corrupt a filesystem without marking  the
              filesystem  dirty  or  in  error.  If you are using
              journaling on your filesystem, your filesystem will
              never  be  marked dirty, so it will not normally be
              checked.  A filesystem error detected by the kernel
              will still force an fsck on the next reboot, but it
              may already be too late to  prevent  data  loss  at
              that point.

              See also the -i option for time-dependent checking.

       -C mount-count
              Set the number of times  the  filesystem  has  been
              mounted.   Can  be  used  in conjunction with -c to
              force an fsck on the filesystem at the next reboot.

       -e error-behavior
              Change  the behavior of the kernel code when errors
              are detected.  In all  cases,  a  filesystem  error
              will cause e2fsck(8) to check the filesystem on the
              next boot.  error-behavior can be one of  the  fol­
              able.

              WARNING:   Removing  an  external  journal  from  a
              filesystem which was not cleanly unmounted  without
              first  replaying the external journal can result in
              severe data loss and filesystem corruption.

       -g group
              Set the group which  can  use  reserved  filesystem
              blocks.  The group parameter can be a numerical gid
              or a group name.  If a group name is given,  it  is
              converted to a numerical gid before it is stored in
              the superblock.

       -i  interval-between-checks[d|m|w]
              Adjust the  maximal  time  between  two  filesystem
              checks.   No  postfix  or  d  result  in days, m in
              months, and w in weeks.  A value of zero will  dis­
              able the time-dependent checking.

              It  is  strongly recommended that either -c (mount-
              count-dependent) or -i (time-dependent) checking be
              enabled  to  force periodic full e2fsck(8) checking
              of the filesystem.  Failure to do so  may  lead  to
              filesystem  corruption  due  to  bad disks, cables,
              memory, or kernel bugs to go unnoticed  until  they
              cause data loss or corruption.

       -j     Add  an  ext3 journal to the filesystem.  If the -J
              option is not specified, the default journal param­
              eters will be used to create an appropriately sized
              journal (given the size of the  filesystem)  stored
              within the filesystem.  Note that you must be using
              a kernel which has ext3 support in order  to  actu­
              ally make use of the journal.

       -J journal-options
              Override the default ext3 journal parameters. Jour­
              nal options are comma separated, and  may  take  an
              argument using the equals ('=')  sign.  The follow­
              ing journal options are supported:

                   size=journal-size
                          Create a journal stored in the filesys­
                          tem  of  size  journal-size  megabytes.
                          The size of  the  journal  must  be  at
                          least 1024 filesystem blocks (i.e., 1MB
                          if using 1k blocks,  4MB  if  using  4k
                          blocks,  etc.)  and may be no more than
                          102,400 filesystem blocks.  There  must
                          be  enough free space in the filesystem
                          to create a journal of that size.
                          directly, external-journal can also  be
                          specified   by  either  LABEL=label  or
                          UUID=UUID to locate the external  jour­
                          nal  by either the volume label or UUID
                          stored in the ext2  superblock  at  the
                          start  of the journal.  Use dumpe2fs(8)
                          to display a  journal  device's  volume
                          label and UUID.  See also the -L option
                          of tune2fs(8).

              Only one of the size or device options can be given
              for a filesystem.

       -l     List the contents of the filesystem superblock.

       -L volume-label
              Set  the  volume  label  of  the  filesystem.  Ext2
              filesystem labels can  be  at  most  16  characters
              long; if volume-label is longer than 16 characters,
              tune2fs will truncate it and print a warning.   The
              volume  label can be used by mount(8), fsck(8), and
              /etc/fstab(5) (and possibly others)  by  specifying
              LABEL=volume_label   instead  of  a  block  special
              device name like /dev/hda5.

       -m reserved-blocks-percentage
              Set the percentage of reserved filesystem blocks.

       -M last-mounted-directory
              Set the last-mounted directory for the  filesystem.

       -o [^]mount-option[,...]
              Set or clear the indicated default mount options in
              the filesystem.  Default mount options can be over­
              riden   by   mount   options  specified  either  in
              /etc/fstab(5) or on the command line  arguments  to
              mount(8).   Older kernels may not support this fea­
              ture; in particular, kernels which  predate  2.4.20
              will  almost  certainly  ignore  the  default mount
              options field in the superblock.

              More than one mount option can be cleared or set by
              separating  features  with  commas.   Mount options
              prefixed with  a  caret  character  ('^')  will  be
              cleared   in  the  filesystem's  superblock;  mount
              options without a prefix character or prefixed with
              a  plus  character  ('+')  will  be  added  to  the
              filesystem.

              The following mount options can be set  or  cleared
              using tune2fs:

                          if it is directory itself.

                   user_xattr
                          Enable     user-specified      extended
                          attributes.

                   acl    Enable Posix Access Control Lists.

                   uid16  Disables 32-bit UIDs and GIDs.  This is
                          for interoperability with older kernels
                          which only store and expect 16-bit val­
                          ues.

                   journal_data
                          When the  filesystem  is  mounted  with
                          journalling enabled, all data (not just
                          metadata) is committed into the journal
                          prior  to  being  written into the main
                          filesystem.

                   journal_data_ordered
                          When the  filesystem  is  mounted  with
                          journalling enabled, all data is forced
                          directly out to the  main  file  system
                          prior  to  its metadata being commutted
                          to the journal.

                   journal_data_writeback
                          When the  filesystem  is  mounted  with
                          journalling  enabled, data may be writ­
                          ten into the main filesystem after  its
                          metadata  has  been  commutted  to  the
                          journal.  This may increase throughput,
                          however,  it  may  allow  old  data  to
                          appear in files after a crash and jour­
                          nal recovery.

       -O [^]feature[,...]
              Set  or  clear  the  indicated  filesystem features
              (options)  in  the  filesystem.   More   than   one
              filesystem  feature  can be cleared or set by sepa­
              rating features with commas.   Filesystem  features
              prefixed  with  a  caret  character  ('^')  will be
              cleared in the filesystem's superblock;  filesystem
              features  without  a  prefix  character or prefixed
              with a plus character ('+') will be  added  to  the
              filesystem.

              The  following  filesystem  features  can be set or
              cleared using tune2fs:

                   dir_index
                          Limit  the number of backup superblocks
                          to save space on large filesystems.

              After setting or clearing sparse_super and filetype
              filesystem  features,  e2fsck(8) must be run on the
              filesystem to return the filesystem to a consistent
              state.   Tune2fs  will  print  a message requesting
              that the system administrator run e2fsck(8) if nec­
              essary.

              Warning:  Linux  kernels before 2.0.39 and many 2.1
              series kernels do not support the filesystems  that
              use   any  of  these  features.   Enabling  certain
              filesystem features may prevent the filesystem from
              being mounted by kernels which do not support those
              features.

       -r reserved-blocks-count
              Set the number of reserved filesystem blocks.

       -s [0|1]
              Turn the sparse super feature off or  on.   Turning
              this  feature on saves space on really big filesys­
              tems.   This  is  the  same   as   using   the   -O
              sparse_super option.

              Warning: Linux kernels before 2.0.39 do not support
              this feature.  Neither do all  Linux  2.1  kernels;
              please  don't  use this unless you know what you're
              doing!  You need to run e2fsck(8) on the filesystem
              after  changing  this  feature  in  order to have a
              valid filesystem.

       -T time-last-checked
              Set the time the filesystem was last checked  using
              e2fsck.   This can be useful in scripts which use a
              Logical Volume Manager to make a  consistent  snap­
              shot of a filesystem, and then check the filesystem
              during off hours to make sure it hasn't  been  cor­
              rupted  due  to  hardware  problems,  etc.   If the
              filesystem was clean, then this option can be  used
              to  set  the  last  checked  time  on  the original
              filesystem.  The format of time-last-checked is the
              international  date  format,  with an optional time
              specifier, i.e.  YYYYMMDD[[HHMM]SS].   The  keyword
              now  is  also  accepted,  in  which  case  the last
              checked time will be set to the current time.

       -u user
              Set the user who can use  the  reserved  filesystem
              blocks.   user  can  be  a  numerical uid or a user
              name.  If a user name is given, it is converted  to
                   time   generate a new time-based UUID

              The UUID may be  used  by  mount(8),  fsck(8),  and
              /etc/fstab(5)  (and  possibly others) by specifying
              UUID=uuid instead of a block  special  device  name
              like /dev/hda1.

              See uuidgen(8) for more information.  If the system
              does not have a good random number  generator  such
              as  /dev/random or /dev/urandom, tune2fs will auto­
              matically use a time-based UUID instead of  a  ran­
              domly-generated UUID.


BUGS

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


AUTHOR

       tune2fs was written by  Remy  Card  <Remy.Card@linux.org>.
       tune2fs  uses  the ext2fs library written by Theodore Ts'o
       <tytso@mit.edu>.  This manual page was written  by  Chris­
       tian  Kuhtz <chk@data-hh.Hanse.DE>.  Time-dependent check­
       ing was added by Uwe Ohse <uwe@tirka.gun.de>.


AVAILABILITY

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


SEE ALSO

       dumpe2fs(8), e2fsck(8), mke2fs(8)

E2fsprogs version 1.34      July 2003                  TUNE2FS(8)
  

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