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NAME    [Toc]    [Back]

       tune2fs	-  adjust  tunable  filesystem	parameters  on second extended

SYNOPSIS    [Toc]    [Back]

       tune2fs [ -l ] [ -c max-mount-counts ] [ -e errors-behavior ] [ -f ]  [
       -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[,...]   ]  [  -T
       time-last-checked ] [ -U UUID ] device

DESCRIPTION    [Toc]    [Back]

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

OPTIONS    [Toc]    [Back]

       -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 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.

       -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:

			  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.

			  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

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

       -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=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 [^]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

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

			  Store file type information in directory entries.

			  Create  an ext3 journal (as if 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 necessary.

	      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

       -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

       -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

	      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    [Toc]    [Back]

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

AUTHOR    [Toc]    [Back]

       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 Christian Kuhtz <chk@data-hh.Hanse.DE>.	 Timedependent
 checking was added by Uwe Ohse <uwe@tirka.gun.de>.

AVAILABILITY    [Toc]    [Back]

       tune2fs	is  part  of  the  e2fsprogs  package  and  is	available from

SEE ALSO    [Toc]    [Back]

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

E2fsprogs version 1.27		  March 2002			    TUNE2FS(8)
[ Back ]
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