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Linux 2.6 - man page for fsck (linux section 8)


       fsck - check and repair a Linux file system

       fsck [-lsAVRTMNP] [-C [fd]] [-t fstype] [filesys...]  [--] [fs-specific-options]

       fsck  is  used to check and optionally repair one or more Linux file systems.  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).  Normally, the fsck program will try to handle filesystems on different phys-
       ical disk drives in parallel to reduce the total amount of time needed to check all of the

       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	 - File system errors corrected
	    2	 - System should be rebooted
	    4	 - File system errors left uncorrected
	    8	 - Operational error
	    16	 - Usage or syntax error
	    32	 - Fsck canceled by user request
	    128  - Shared library error
       The exit code returned when multiple file systems are checked is the bit-wise  OR  of  the
       exit codes for each file system that is checked.

       In   actuality,	fsck  is  simply  a  front-end	for  the  various  file  system  checkers
       (fsck.fstype) available under Linux.  The file system-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 file system-specific checker manual pages	for  fur-
       ther details.

       -l     Lock  whole-disk	device	by  exclusive flock(2).  This option can be used with one
	      device only (e.g. -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 disk. The  fsck  does	not  lock
	      underlying  devices  if  executed  to check stacked devices (e.g. MD or DM) -- this
	      feature is not implemented yet.

       -s     Serialize fsck operations.  This is a  good  idea  if  you  are  checking  multiple
	      filesystems  and the checkers are in an interactive 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 file system 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  all
	      of  the  filesystems  in	fslist are not prefixed by a negation operator, then only
	      those filesystems listed in fslist 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 filesys-
	      tems which contain 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

	      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  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
	      file system type (currently ext2) is used.

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

	      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 low-
	      est 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  filesys-
	      tem  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  check-
	      ers in parallel if it is advantageous to do so.  System administrators might choose
	      not to use this configuration if they need to avoid multiple filesystem checks run-
	      ning  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
	      file  system  specific checker. Therefore non-existing devices may cause the system
	      to enter file system 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-existing devices that have the spe-
	      cial file system 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
	      specify a file descriptor fd, in which case the progress bar  information  will  be
	      sent to that file descriptor.

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

       -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 repartition
	      the root filesystem to be small and compact (which is really the right solution).

       -R     When checking all file systems with the -A flag, skip the root file system (in case
	      it's already mounted read-write).

       -T     Don't show the title on startup.

       -V     Produce  verbose	output, including all file system-specific commands that are exe-

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

	      Options and arguments which follow the  --  are  treated	as  file  system-specific
	      options to be passed to the file system-specific checker.

	      Please  note  that  fsck is not designed to pass arbitrarily complicated 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
	      complicated option and arguments, and it doesn't do what you expect,  don't  bother
	      reporting  it as a bug.  You're almost certainly 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 file system checkers:

       -a     Automatically repair the file system without any questions (use  this  option  with
	      caution).   Note that e2fsck(8) supports -a for backwards compatibility only.  This
	      option is mapped to e2fsck's -p option which is safe to use, unlike the  -a  option
	      that some file system 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 partic-
	      ular, 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 backwards
	      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  particular
	      fsck.minix(8) and fsck.cramfs(8) does not support the -y option as of this writing.

       Theodore Ts'o (tytso@mit.edu)

       The fsck command is part of the util-linux package and is  available  from  ftp://ftp.ker-


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

	      If  this environment variable is set, fsck will attempt to run 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

	      This  environment  variable  will  limit the maximum number of file system checkers
	      that can be running at one time.	This allows configurations  which  have  a  large
	      number of disks to avoid fsck starting too many file system 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  file  system  checks  can  be run based on gathering accounting data from the
	      operating system.

       PATH   The PATH environment variable is used to find file system checkers.  A set of  sys-
	      tem directories are searched first: /sbin, /sbin/fs.d, /sbin/fs, /etc/fs, and /etc.
	      Then the set of directories found in the PATH environment are searched.

	      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

       fstab(5), mkfs(8), fsck.ext2(8) or fsck.ext3(8) or e2fsck(8), cramfsck(8),  fsck.minix(8),
       fsck.msdos(8),  fsck.jfs(8),  fsck.nfs(8), fsck.vfat(8), fsck.xfs(8), fsck.xiafs(8), reis-

Linux					  February 2009 				  FSCK(8)

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