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FSCK(8)			     System Administration		       FSCK(8)

NAME
       fsck - check and	repair a Linux filesystem

SYNOPSIS
       fsck [-lrsAVRTMNP] [-C [fd]] [-t	fstype]	[filesystem...]	 [--] [fs-spe-
       cific-options]

DESCRIPTION
       fsck is used to check and optionally repair one or more Linux  filesys-
       tems.   filesys	can  be	 a device name (e.g.  /dev/hdc1, /dev/sdb2), a
       mount point (e.g.  /, /usr, /home), or an ext2 label or UUID  specifier
       (e.g.   UUID=8868abf6-88c5-4a83-98b8-bfc24057f7bd or LABEL=root).  Nor-
       mally, the fsck program will try	to  handle  filesystems	 on  different
       physical	 disk  drives  in  parallel to reduce the total	amount of time
       needed to check all of them.

       If no filesystems are specified on the command line, and	the -A	option
       is  not	specified,  fsck  will	default	 to  checking  filesystems  in
       /etc/fstab serially.  This is equivalent	to the -As options.

       The exit	code returned by fsck is the sum of the	following conditions:

	      0	     No	errors
	      1	     Filesystem	errors corrected
	      2	     System should be rebooted
	      4	     Filesystem	errors left uncorrected
	      8	     Operational error
	      16     Usage or syntax error
	      32     Checking canceled by user request
	      128    Shared-library error

       The exit	code returned when multiple filesystems	 are  checked  is  the
       bit-wise	OR of the exit codes for each filesystem that is checked.

       In  actuality,  fsck  is	 simply	a front-end for	the various filesystem
       checkers	(fsck.fstype) available	under Linux.  The  filesystem-specific
       checker	is  searched for in /sbin first, then in /etc/fs and /etc, and
       finally in the directories listed in  the  PATH	environment  variable.
       Please see the filesystem-specific checker manual pages for further de-
       tails.

OPTIONS
       -l     Lock the whole-disk device by an exclusive flock(2).   This  op-
	      tion can be used with one	device only (this means	that -A	and -l
	      are mutually exclusive).	This option is recommended  when  more
	      fsck(8)  instances are executed in the same time.	 The option is
	      ignored when used	 for  multiple	devices	 or  for  non-rotating
	      disks.   fsck  does not lock underlying devices when executed to
	      check stacked devices (e.g. MD or	DM) -- this feature is not im-
	      plemented	yet.

       -r     Report certain statistics	for each fsck when it completes. These
	      statistics include the exit status, the maximum run set size (in
	      kilobytes),  the	elapsed	all-clock time and the user and	system
	      CPU time used by the fsck	run. For example:

	      /dev/sda1: status	0, rss 92828, real  4.002804,  user  2.677592,
	      sys 0.86186

       -s     Serialize	 fsck  operations.   This  is  a  good idea if you are
	      checking multiple	filesystems and	the checkers are in an	inter-
	      active  mode.   (Note:  e2fsck(8)	runs in	an interactive mode by
	      default.	To make	e2fsck(8) run in a non-interactive  mode,  you
	      must  either specify the -p or -a	option,	if you wish for	errors
	      to be corrected automatically, or	the -n option if you do	not.)

       -t fslist
	      Specifies	the type(s) of filesystem to be	checked.  When the  -A
	      flag  is	specified,  only  filesystems  that  match  fslist are
	      checked.	The fslist parameter  is  a  comma-separated  list  of
	      filesystems  and	options	specifiers.  All of the	filesystems in
	      this comma-separated list	may be prefixed	by a negation operator
	      'no'  or	'!',  which  requests  that only those filesystems not
	      listed in	fslist will be checked.	 If none of the	filesystems in
	      fslist  is  prefixed  by	a  negation  operator, then only those
	      listed filesystems will be checked.

	      Options specifiers may be	included in  the  comma-separated  fs-
	      list.   They must	have the format	opts=fs-option.	 If an options
	      specifier	is present, then only filesystems which	contain	fs-op-
	      tion in their mount options field	of /etc/fstab will be checked.
	      If the options specifier is prefixed  by	a  negation  operator,
	      then  only those filesystems that	do not have fs-option in their
	      mount options field of /etc/fstab	will be	checked.

	      For example, if opts=ro appears in fslist, then only filesystems
	      listed in	/etc/fstab with	the ro option will be checked.

	      For compatibility	with Mandrake distributions whose boot scripts
	      depend upon an unauthorized UI change to the fsck	program, if  a
	      filesystem  type of loop is found	in fslist, it is treated as if
	      opts=loop	were specified as an argument to the -t	option.

	      Normally,	the  filesystem	 type  is  deduced  by	searching  for
	      filesys  in  the /etc/fstab file and using the corresponding en-
	      try.  If the type	can not	be deduced, and	there is only a	single
	      filesystem  given	as an argument to the -t option, fsck will use
	      the specified filesystem type.  If this type is  not  available,
	      then the default filesystem type (currently ext2)	is used.

       -A     Walk  through  the /etc/fstab file and try to check all filesys-
	      tems in one run.	This option is typically used from the /etc/rc
	      system  initialization  file,  instead  of multiple commands for
	      checking a single	filesystem.

	      The root filesystem will be checked first	unless the  -P	option
	      is  specified  (see  below).   After  that,  filesystems will be
	      checked in the order specified  by  the  fs_passno  (the	sixth)
	      field  in	 the  /etc/fstab  file.	  Filesystems with a fs_passno
	      value of 0 are skipped and are not checked at all.   Filesystems
	      with  a  fs_passno value of greater than zero will be checked in
	      order, with filesystems with the lowest fs_passno	 number	 being
	      checked  first.  If there	are multiple filesystems with the same
	      pass number, fsck	will attempt to	check them  in	parallel,  al-
	      though  it  will avoid running multiple filesystem checks	on the
	      same physical disk.

	      fsck does	not check stacked devices (RAIDs,  dm-crypt,  ...)  in
	      parallel	  with	  any	 other	  device.    See   below   for
	      FSCK_FORCE_ALL_PARALLEL setting.	The /sys filesystem is used to
	      detemine dependencies between devices.

	      Hence, a very common configuration in /etc/fstab files is	to set
	      the root filesystem to have a fs_passno value of 1  and  to  set
	      all other	filesystems to have a fs_passno	value of 2.  This will
	      allow fsck to automatically run filesystem checkers in  parallel
	      if  it  is  advantageous	to do so.  System administrators might
	      choose not to use	this configuration if they need	to avoid  mul-
	      tiple  filesystem	checks running in parallel for some reason ---
	      for example, if the machine in question is short	on  memory  so
	      that excessive paging is a concern.

	      fsck  normally does not check whether the	device actually	exists
	      before calling a filesystem specific checker.  Therefore non-ex-
	      isting  devices  may cause the system to enter filesystem	repair
	      mode during boot if the filesystem specific  checker  returns  a
	      fatal  error.  The /etc/fstab mount option nofail	may be used to
	      have fsck	skip non-existing devices.  fsck also skips non-exist-
	      ing devices that have the	special	filesystem type	auto.

       -C [fd]
	      Display  completion/progress  bars for those filesystem checkers
	      (currently only for ext2 and ext3)  which	 support  them.	  fsck
	      will  manage  the	 filesystem  checkers so that only one of them
	      will display a progress bar at a time.  GUI front-ends may spec-
	      ify  a file descriptor fd, in which case the progress bar	infor-
	      mation will be sent to that file descriptor.

       -M     Do not check mounted filesystems and return an exit  code	 of  0
	      for mounted filesystems.

       -N     Don't execute, just show what would be done.

       -P     When  the	 -A flag is set, check the root	filesystem in parallel
	      with the other filesystems.  This	is not the safest thing	in the
	      world  to	 do,  since  if	the root filesystem is in doubt	things
	      like the e2fsck(8) executable might be corrupted!	  This	option
	      is  mainly provided for those sysadmins who don't	want to	repar-
	      tition the root filesystem to be small and compact (which	is re-
	      ally the right solution).

       -R     When  checking  all  filesystems with the	-A flag, skip the root
	      filesystem.  (This is useful in case the root filesystem has al-
	      ready been mounted read-write.)

       -T     Don't show the title on startup.

       -V     Produce  verbose	output,	including all filesystem-specific com-
	      mands that are executed.

       fs-specific-options
	      Options which are	not understood	by  fsck  are  passed  to  the
	      filesystem-specific  checker.  These options must	not take argu-
	      ments, as	there is no way	for fsck to be able to properly	 guess
	      which options take arguments and which don't.

	      Options  and  arguments  which  follow  the  --  are  treated as
	      filesystem-specific options to be	passed to the  filesystem-spe-
	      cific checker.

	      Please  note  that fsck is not designed to pass arbitrarily com-
	      plicated options to filesystem-specific checkers.	 If you're do-
	      ing  something  complicated, please just execute the filesystem-
	      specific checker directly.  If you pass fsck some	horribly  com-
	      plicated	options	 and arguments,	and it doesn't do what you ex-
	      pect, don't bother reporting it as a bug.	  You're  almost  cer-
	      tainly doing something that you shouldn't	be doing with fsck.

       Options	to  different filesystem-specific fsck's are not standardized.
       If in doubt, please consult the man pages  of  the  filesystem-specific
       checker.	  Although not guaranteed, the following options are supported
       by most filesystem checkers:

       -a     Automatically repair the filesystem without any  questions  (use
	      this  option with	caution).  Note	that e2fsck(8) supports	-a for
	      backward compatibility only.  This option	is mapped to  e2fsck's
	      -p  option  which	is safe	to use,	unlike the -a option that some
	      filesystem checkers support.

       -n     For some filesystem-specific checkers, the -n option will	 cause
	      the fs-specific fsck to avoid attempting to repair any problems,
	      but simply report	such problems to stdout.  This is however  not
	      true  for	 all  filesystem-specific  checkers.   In  particular,
	      fsck.reiserfs(8) will not	report any corruption  if  given  this
	      option.  fsck.minix(8) does not support the -n option at all.

       -r     Interactively  repair  the  filesystem  (ask for confirmations).
	      Note: It is generally a bad idea to use this option if  multiple
	      fsck's  are  being  run  in  parallel.   Also  note that this is
	      e2fsck's default behavior; it supports this option for  backward
	      compatibility reasons only.

       -y     For  some	filesystem-specific checkers, the -y option will cause
	      the fs-specific fsck to  always  attempt	to  fix	 any  detected
	      filesystem corruption automatically.  Sometimes an expert	may be
	      able to do better	driving	the fsck manually.  Note that not  all
	      filesystem-specific checkers implement this option.  In particu-
	      lar fsck.minix(8)	and fsck.cramfs(8) do not support the  -y  op-
	      tion as of this writing.

FILES
       /etc/fstab.

ENVIRONMENT VARIABLES
       The  fsck  program's  behavior is affected by the following environment
       variables:

       FSCK_FORCE_ALL_PARALLEL
	      If this environment variable is set, fsck	will attempt to	 check
	      all  of  the  specified  filesystems  in parallel, regardless of
	      whether the filesystems appear to	be on the same device.	 (This
	      is  useful  for RAID systems or high-end storage systems such as
	      those sold by companies such as IBM  or  EMC.)   Note  that  the
	      fs_passno	value is still used.

       FSCK_MAX_INST
	      This  environment	 variable  will	 limit	the  maximum number of
	      filesystem checkers that can be running at one time.   This  al-
	      lows  configurations which have a	large number of	disks to avoid
	      fsck starting too	many filesystem	checkers at once, which	 might
	      overload	CPU  and memory	resources available on the system.  If
	      this value is zero, then an unlimited number of processes	can be
	      spawned.	 This is currently the default,	but future versions of
	      fsck may attempt to automatically	determine how many  filesystem
	      checks  can  be  run based on gathering accounting data from the
	      operating	system.

       PATH   The PATH environment variable is used to find filesystem	check-
	      ers.   A	set  of	 system	directories are	searched first:	/sbin,
	      /sbin/fs.d, /sbin/fs, /etc/fs, and /etc.	Then the set of	direc-
	      tories found in the PATH environment are searched.

       FSTAB_FILE
	      This  environment	 variable  allows  the system administrator to
	      override the standard location of	the /etc/fstab	file.	It  is
	      also useful for developers who are testing fsck.

       LIBBLKID_DEBUG=0xffff
	      enables debug output.

       LIBMOUNT_DEBUG=0xffff
	      enables debug output.

SEE ALSO
       fstab(5),  mkfs(8),  fsck.ext2(8)  or fsck.ext3(8) or e2fsck(8),	cramf-
       sck(8),	 fsck.minix(8),	  fsck.msdos(8),   fsck.jfs(8),	  fsck.nfs(8),
       fsck.vfat(8), fsck.xfs(8), fsck.xiafs(8), reiserfsck(8).

AUTHOR
       Theodore	Ts'o <tytso@mit.edu>

AVAILABILITY
       The  fsck  command  is  part of the util-linux package and is available
       from Linux Kernel  Archive  <ftp://ftp.kernel.org/pub/linux/utils/util-
       linux/>.

util-linux			 February 2009			       FSCK(8)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | FILES | ENVIRONMENT VARIABLES | SEE ALSO | AUTHOR | AVAILABILITY

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