FSCK(8) 						       MAINTENANCE COMMANDS							   FSCK(8)

NAME

       fsck - check and repair a Linux file system

SYNOPSIS

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

DESCRIPTION

       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 physical disk drives in parallel to reduce the total amount of time
       needed to check all of the filesystems.

       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-spe-
       cific checker is searched for in /sbin first, then in /etc/fs and /etc, and finally in the directories listed in the PATH environment vari-
       able.  Please see the file system-specific checker manual pages for further details.

OPTIONS

       -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-sepa-
	      rated  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 speci-
	      fier 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 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 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 sys-
	      tem 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  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.

	      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 multiple  filesys-
	      tem checks running in parallel for some reason --- for example, if the machine in question is short on memory so that excessive pag-
	      ing is a concern.

	      fsck normally does not check whether the device actually exists before calling a file system specific checker. Therefore	non-exist-
	      ing  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 special 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 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 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 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 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  some-
	      thing 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 particular, fsck.reis-
	      erfs(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  filesys-
	      tem  corruption  automatically.  Sometimes an expert may be able to do better driving the fsck manually.	Note that not all filesys-
	      tem-specific checkers implement this option.  In particular fsck.minix(8) and fsck.cramfs(8) does not support the -y  option  as	of
	      this writing.

AUTHOR

       Theodore Ts'o (tytso@mit.edu)

AVAILABILITY

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

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 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.)

       FSCK_MAX_INST
	      This  environment  variable will limit the maximum number of file system checkers that can be running at one time.  This allows con-
	      figurations 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 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 use-
	      ful 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).

Linux								   February 2009							   FSCK(8)