dosfsck

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 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  re-
           named.

       *   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  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 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 dis-
       abled with the -w option.

OPTIONS
       -a  Automatically  repair the filesystem.  No user intervention is nec-
           essary.  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  for-
           mat.   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.  Un-
           der MS-DOS 0xfff8 is used for EOF and Atari employs 0xffff  by  de-
           fault,  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 code-
           page 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 clus-
           ters 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 back-
           wards 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 af-
           ter the first run.  The second pass should never report any fixable
           errors.   It  may take considerably longer than the first pass, be-
           cause 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 inconsistency.

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

FILES
       fsck0000.rec, fsck0001.rec, ...
           When  recovering from a corrupted filesystem, fsck.fat dumps recov-
           ered data into files named 'fsckNNNN.rec' in the top  level  direc-
           tory of the filesystem.

BUGS
       Does  not  create  . and .. files where necessary.  Does not remove en-
       tirely empty directories.  Should give more diagnostic  messages.   Un-
       deleting 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 maintainer is Andreas Bombe <aeb@debian.org>.

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