Provided by: e2fsprogs_1.38-2ubuntu2_i386 bug

NAME

       tune2fs - adjust tunable filesystem parameters on ext2/ext3 filesystems

SYNOPSIS

       tune2fs [ -l ] [ -c max-mount-counts ] [ -e errors-behavior ] [ -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  allows  the  system  administrator  to  adjust various tunable
       filesystem parameters on Linux ext2/ext3 filesystems.

OPTIONS

       -c max-mount-counts
              Adjust the maximal mounts count between two  filesystem  checks.
              If  max-mount-counts  is  0  or  -1,  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 following:

                   continue    Continue normal execution.

                   remount-ro  Remount filesystem read-only.

                   panic       Cause a kernel panic.

       -f     Force the tune2fs operation to complete  even  in  the  face  of
              errors.   This  option  is  useful when removing the has_journal
              filesystem feature from  a  filesystem  which  has  an  external
              journal  (or  is  corrupted  such  that  it  appears  to have an
              external journal), but that external journal is not available.

              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 disable 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 parameters 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 actually make
              use of the journal.

              If this option  is  used  to  create  a  journal  on  a  mounted
              filesystem,  an immutable file, .journal, will be created in the
              top-level directory of the filesystem, as it is  the  only  safe
              way to create the journal inode while the filesystem is mounted.
              While the ext3 journal is visible, it is not safe to delete  it,
              or  modify  it  while the filesystem is mounted; for this reason
              the  file  is  marked  immutable.   While   checking   unmounted
              filesystems, e2fsck(8) will automatically move .journal files to
              the invisible, reserved  journal  inode.   For  all  filesystems
              except   for   the   root   filesystem,    this   should  happen
              automatically and naturally during the next reboot cycle.  Since
              the  root filesystem is mounted read-only, e2fsck(8) must be run
              from a rescue floppy in order to effect this transition.

              On some distributions, such as Debian, if an initial ramdisk  is
              used, the initrd scripts will automatically convert an ext2 root
              filesystem to ext3 if the /etc/fstab  file  specifies  the  ext3
              filesystem  for  the root filesystem in order to avoid requiring
              the use of a rescue floppy to add an ext3 journal  to  the  root
              filesystem.

       -J journal-options
              Override  the  default  ext3 journal parameters. Journal options
              are comma separated, and may take an argument using  the  equals
              (’=’)  sign.  The following journal options are supported:

                   size=journal-size
                          Create  a  journal  stored in the filesystem 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 block device
                          located on external-journal.  The  external  journal
                          must have been already created using the command

                          mke2fs -O journal_dev external-journal

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

                          Instead   of  specifying  a  device  name  directly,
                          external-journal can also  be  specified  by  either
                          LABEL=label  or  UUID=UUID  to  locate  the external
                          journal 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  overridden  by  mount
              options specified either in /etc/fstab(5) or on the command line
              arguments to mount(8).   Older  kernels  may  not  support  this
              feature; 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:

                   debug  Enable debugging code for this filesystem.

                   bsdgroups
                          Emulate BSD behaviour when creating new files:  they
                          will  take  the  group-id  of the directory in which
                          they were created.  The standard System V  behaviour
                          is  the  default,  where newly created files take on
                          the  fsgid  of  the  current  process,  unless   the
                          directory  has  the setgid bit set, in which case it
                          takes the gid from the parent  directory,  and  also
                          gets the setgid bit set 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 values.

                   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 committed to
                          the journal.

                   journal_data_writeback
                          When  the  filesystem  is  mounted  with journalling
                          enabled,  data  may  be  written   into   the   main
                          filesystem  after its metadata has been committed to
                          the journal.  This may increase throughput, however,
                          it  may  allow  old  data to appear in files after a
                          crash and journal 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 separating 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
                          Use  hashed  b-trees  to  speed  up lookups in large
                          directories.

                   filetype
                          Store file type information in directory entries.

                   has_journal
                          Use a journal to ensure filesystem consistency  even
                          across  unclean  shutdowns.   Setting the filesystem
                          feature is equivalent to using the -j option.

                   sparse_super
                          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
              necessary.   After  setting the dir_index feature, e2fsck -D can
              be run to convert existing  directories  to  the  hashed  B-tree
              format.

              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 filesystems.  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 snapshot of a filesystem, and then check the
              filesystem  during  off  hours  to  make  sure  it  hasn’t  been
              corrupted  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 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         hyphens,         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

              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 automatically use a  time-based  UUID
              instead of a randomly-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>.   It  is
       currently  being  maintained  by  Theodore  Ts’o  <tytso@alum.mit.edu>.
       tune2fs   uses   the   ext2fs   library   written   by   Theodore  Ts’o
       <tytso@mit.edu>.  This manual  page  was  written  by  Christian  Kuhtz
       <chk@data-hh.Hanse.DE>.   Time-dependent checking 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)