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
       details.

OPTIONS
       -l     Lock the whole-disk  device  by  an  exclusive  flock(2).	  This
	      option  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 exe-
	      cuted to check stacked devices (e.g. MD or DM) --	 this  feature
	      is not implemented 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
	      fslist.	They  must  have  the  format  opts=fs-option.	 If an
	      options specifier is present, then only filesystems  which  con-
	      tain  fs-option  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
	      entry.  If the type can not be deduced, and there is only a sin-
	      gle  filesystem given as an argument to the -t option, fsck will
	      use the specified filesystem type.  If this type is  not	avail-
	      able, 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,
	      although 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-
	      existing 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
	      really 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
	      already 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
	      doing 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
	      expect, 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
	      option 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
	      allows  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 filesys-
	      tem  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)