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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  pro-
       gram  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 spec-
       ified,  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 man-
       ual 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-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 filesystems which contain fs-option in their  mount  options  field  of
              /etc/fstab will be checked.  If the options specifier is prefixed by a nega-
              tion 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 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 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 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 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 call-
              ing 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 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  filesys-
              tem 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-spe-
              cific 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-spe-
              cific 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  compli-
              cated, 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 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 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-spe-
              cific fsck to avoid attempting to repair any  problems,  but  simply  report
              such  problems  to stdout.  This is however not true for all filesystem-spe-
              cific checkers.  In particular, fsck.reiserfs(8) will not report any corrup-
              tion  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-spe-
              cific fsck to always attempt to fix any detected filesystem corruption auto-
              matically.   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.

AUTHOR
       Theodore Ts'o (tytso AT 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.)
              Note that the fs_passno value is still used.

       FSCK_MAX_INST
              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  system  directories  are  searched  first:  /sbin, /sbin/fs.d, /sbin/fs,
              /etc/fs, and /etc.  Then the set of directories found in the  PATH  environ-
              ment 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).



Linux                            February 2009                         FSCK(8)

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