FSCK(8) 					       System Administration						   FSCK(8)



NAME
       fsck - check and repair a Linux filesystem

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

DESCRIPTION
       fsck  is used to check and optionally repair one or more Linux filesystems.  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 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	 - Fsck 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  underly‐
	      ing devices when 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-interac‐
	      tive 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	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  filesys‐
	      tems 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 argu‐
	      ment 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 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  (cur‐
	      rently ext2) is used.

       -A     Walk  through  the  /etc/fstab file and try to check all filesystems 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 filesys‐
	      tem checkers in parallel if it is advantageous to do so.	System administrators might choose not to use this config‐
	      uration if they need to avoid multiple 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-exist‐
	      ing devices.  fsck also skips non-existing 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  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 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 repartition 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 filesys‐
	      tem has already been mounted read-write.)

       -T     Don't show the title on startup.

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

       fs-specific-options
	      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 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-
	      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 options 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 filesystem checkers:

       -a     Automatically  repair the filesystem without any questions (use this option with caution).  Note that e2fsck(8) sup‐
	      ports -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 manu‐
	      ally.  Note that not all filesystem-specific checkers  implement	this  option.	In  particular	fsck.minix(8)  and
	      fsck.cramfs(8) do not support the -y option as of this writing.

AUTHOR
       Theodore Ts'o (tytso@mit.edu)

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

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 unlim‐
	      ited 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 checkers.  A set of system 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.

       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.

SEE ALSO
       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), reiserfsck(8).



util-linux						   February 2009						   FSCK(8)