<root
FSCK.FAT(8)                                 dosfstools                                FSCK.FAT(8)

NAME
       fsck.fat - check and repair MS-DOS filesystems

SYNOPSIS
       fsck.fat [OPTIONS] DEVICE

DESCRIPTION
       fsck.fat  verifies  the  consistency  of MS-DOS filesystems and optionally tries to repair
       them.

       The following filesystem problems can be corrected (in this order):

       *   FAT contains invalid cluster numbers.  Cluster is changed to EOF.

       *   File's cluster chain contains a loop.  The loop is broken.

       *   Bad clusters (read errors).  The clusters are marked bad and  they  are  removed  from
           files owning them.  This check is optional.

       *   Directories  with a large number of bad entries (probably corrupt).  The directory can
           be deleted.

       *   Files . and .. are non-directories.  They can be deleted or renamed.

       *   Directories . and .. in root directory.  They are deleted.

       *   Bad filenames.  They can be renamed.

       *   Duplicate directory entries.  They can be deleted or renamed.

       *   Directories with non-zero size field.  Size is set to zero.

       *   Directory . does not point to parent directory.  The start pointer is adjusted.

       *   Directory .. does not point to parent of  parent  directory.   The  start  pointer  is
           adjusted.

       *   Start cluster number of a file is invalid.  The file is truncated.

       *   File contains bad or free clusters.  The file is truncated.

       *   File's  cluster  chain is longer than indicated by the size fields.  The file is trun‐
           cated.

       *   Two or more files share the same cluster(s).  All but one of the files are  truncated.
           If  the  file  being  truncated  is  a  directory file that has already been read, the
           filesystem check is restarted after truncation.

       *   File's cluster chain is shorter than indicated by the size fields.  The file is  trun‐
           cated.

       *   Clusters are marked as used but are not owned by a file.  They are marked as free.

       Additionally, the following problems are detected, but not repaired:

       *   Invalid parameters in boot sector

       *   Absence of . and .. entries in non-root directories

       When  fsck.fat checks a filesystem, it accumulates all changes in memory and performs them
       only after all checks are complete.  This can be disabled with the -w option.

OPTIONS
       -a  Automatically repair the filesystem.  No user  intervention  is  necessary.   Whenever
           there  is  more  than one method to solve a problem, the least destructive approach is
           used.

       -A  Use Atari variation of the MS-DOS filesystem.  This is default if fsck.fat is  run  on
           an  Atari,  then this option turns off Atari format.  There are some minor differences
           in Atari format: Some boot sector fields are interpreted slightly different,  and  the
           special  FAT  entries  for end-of-file and bad cluster can be different.  Under MS-DOS
           0xfff8 is used for EOF and Atari employs 0xffff by default, but both systems recognize
           all values from 0xfff8...0xffff as end-of-file.  MS-DOS uses only 0xfff7 for bad clus‐
           ters, where on Atari values 0xfff0...0xfff7 are for this  purpose  (but  the  standard
           value is still 0xfff7).

       -b  Make read-only boot sector check.

       -d PATH
           Delete  the specified file.  If more than one file with that name exist, the first one
           is deleted.  This option can be given more than once.

       -f  Salvage unused cluster chains to files.  By default, unused clusters are added to  the
           free disk space except in auto mode (-a).

       -l  List path names of files being processed.

       -n  No-operation mode: non-interactively check for errors, but don't write anything to the
           filesystem.

       -p  Same as -a, for compatibility with other *fsck.

       -r  Interactively repair the filesystem.  The user is asked for advice whenever  there  is
           more  than  one  approach  to  fix an inconsistency.  This is the default mode and the
           option is only retained for backwards compatibility.

       -t  Mark unreadable clusters as bad.

       -u PATH
           Try to undelete the specified file.  fsck.fat tries to allocate a chain of  contiguous
           unallocated  clusters  beginning  with  the start cluster of the undeleted file.  This
           option can be given more than once.

       -v  Verbose mode.  Generates slightly more output.

       -V  Perform a verification pass.  The filesystem check is repeated after  the  first  run.
           The  second  pass  should  never  report any fixable errors.  It may take considerably
           longer than the first pass, because the first pass may have  generated  long  list  of
           modifications that have to be scanned for each disk read.

       -w  Write changes to disk immediately.

       -y  Same as -a (automatically repair filesystem) for compatibility with other fsck tools.

EXIT STATUS
       0   No recoverable errors have been detected.

       1   Recoverable errors have been detected or fsck.fat has discovered an internal inconsis‐
           tency.

       2   Usage error.  fsck.fat did not access the filesystem.

FILES
       fsck0000.rec, fsck0001.rec, ...
           When recovering from a corrupted filesystem, fsck.fat dumps recovered data into  files
           named 'fsckNNNN.rec' in the top level directory of the filesystem.

BUGS
       Does  not  create . and .. files where necessary.  Does not remove entirely empty directo‐
       ries.  Should give more diagnostic messages.  Undeleting files should use a more sophisti‐
       cated algorithm.

SEE ALSO
       fatlabel(8)
       mkfs.fat(8)

HOMEPAGE
       The    home    for    the    dosfstools    project    is    its    GitHub   project   page
       ⟨https://github.com/dosfstools/dosfstools⟩.

AUTHORS
       dosfstools were written by Werner Almesberger  ⟨werner.almesberger@lrc.di.epfl.ch⟩,  Roman
       Hodek  ⟨Roman.Hodek@informatik.uni-erlangen.de⟩,  and  others.   The current maintainer is
       Andreas Bombe ⟨aeb@debian.org⟩.

3.0.28                                      2015-05-16                                FSCK.FAT(8)

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