FSCK.FAT(8)                        System Manager's Manual                       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 re‐
       pair 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
           truncated.

       *   Two or more files share the same cluster(s).  All but one of the files are  trun‐
           cated.   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
           truncated.

       *   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.  When‐
           ever there is more than one method to solve a problem, the least destructive  ap‐
           proach 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  dif‐
           ferences  in  Atari format: Some boot sector fields are interpreted slightly dif‐
           ferent, and the special FAT entries for end-of-file and bad cluster can  be  dif‐
           ferent.  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 clusters, where on Atari values 0xfff0...0xfff7
           are for this purpose (but the standard value is still 0xfff7).

       -b  Make read-only boot sector check.

       -c PAGE
           Use DOS codepage PAGE to decode short file names.  By  default  codepage  437  is
           used.

       -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  con‐
           tiguous  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 con‐
           siderably 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  in‐
           consistency.

       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  di‐
       rectories.  Should give more diagnostic messages.  Undeleting files should use a more
       sophisticated 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  main‐
       tainer is Andreas Bombe ⟨aeb@debian.org⟩.

dosfstools 4.1                           2015-04-16                              FSCK.FAT(8)

usage: fsck.fat [-aAbflrtvVwy] [-d path -d ...] [-u path -u ...]
               device
  -a       automatically repair the filesystem
  -A       toggle Atari filesystem format
  -b       make read-only boot sector check
  -c N     use DOS codepage N to decode short file names (default: 437)
  -d path  drop that file
  -f       salvage unused chains to files
  -l       list path names
  -n       no-op, check non-interactively without changing
  -p       same as -a, for compat with other *fsck
  -r       interactively repair the filesystem (default)
  -t       test for bad clusters
  -u path  try to undelete that (non-directory) file
  -v       verbose mode
  -V       perform a verification pass
  -w       write changes to disk immediately
  -y       same as -a, for compat with other *fsck