tune2fs  -  adjust tunable filesystem parameters on second
       extended filesystems


SYNOPSIS

       tune2fs [ -l ] [ -c max-mount-counts ] [ -e  errors-behav­
       ior  ] [ -i interval-between-checks ] [ -j ] [ -J journal-
       options ] [ -m reserved-blocks-percentage ] [ -r reserved-
       blocks-count  ]  [ -s sparse-super-flag ] [ -u user ] [ -g
       group ] [ -C mount-count ] [ -L volume-name ] [  -M  last-
       mounted-directory  ]  [ -O [^]feature[,...]  ] [ -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
              lowing:


                   remount-ro  Remount filesystem read-only.

                   panic       Cause a kernel panic.

       -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.

                   device=external-journal
                          Attach  the  filesystem  to the journal

                          nal.   The  external  journal must have
                          been already created using the command

                          mke2fs -O journal_dev external-journal

                          Note that external-journal must be for­
                          matted  with  the  same  block  size as
                          filesystems which will be using it.

              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.

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

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

       -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:

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

                   filetype
                          Store  file  type information in direc­
                          tory entries.

                   has_journal
                          Create an ext3 journal (as if using the
                          -j option).

              After  setting  or clearing any filesystem feature,

              the filesystem to a consistent state.

              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.

       -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
              a   numerical  uid  before  it  is  stored  in  the
              superblock.

       -U UUID
              Set the universally unique identifier (UUID) of the
              filesystem  to  UUID.   The format of the UUID is a
              series of hex digits separated  by  hypthens,  like
              this:  "c1b9d5a2-f162-11cf-9ece-0020afc76f16".  The
              UUID parameter may also be one of the following:

                   clear  clear the filesystem UUID

                   random generate a new randomly-generated UUID

                   time   generate a new time-based UUID

              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



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)


Man(1) output converted with man2html