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tune2fs

TUNE2FS(8)                                                          TUNE2FS(8)



NAME
       tune2fs  -  adjust  tunable  filesystem  parameters  on second extended
       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-direc-
       tory ] [ -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 filesys-
              tem 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 jour-
              nal (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 corrup-
              tion.

       -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 post-
              fix 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-depen-
              dent) or -i (time-dependent) checking be enabled to force  peri-
              odic  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  filesys-
              tem)  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.

       -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, exter-
                          nal-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 warn-
              ing.  The volume label can be used  by  mount(8),  fsck(8),  and
              /etc/fstab(5)  (and  possibly  others)  by specifying LABEL=vol-
              ume_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 filesys-
              tem.  Default mount options can be overriden  by  mount  options
              specified  either  in /etc/fstab(5) or on the command line argu-
              ments to mount(8).  Older kernels may not support this  feature;
              in  particular,  kernels  which  predate 2.4.20 will almost cer-
              tainly 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 char-
              acter  ('^')  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 crrent process, unless the directry
                          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 interop-
                          erability 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 commutted 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 commutted 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:

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

                   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.

              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 neces-
              sary.

              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 fea-
              tures.

       -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  fea-
              ture.   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 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 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 sepa-
              rated          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>.   tune2fs  uses
       the ext2fs library written by Theodore Ts'o <tytso@mit.edu>.  This man-
       ual 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)



E2fsprogs version 1.32           November 2002                      TUNE2FS(8)