FSCK.FAT(8)		    System Manager's Manual		   FSCK.FAT(8)

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

       •   . and .. are not the two first entries in a non-root directory.
	   The entries are created, moving occupied slots if necessary.

       •   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.

       •   Volume label in root directory or label in boot sector is invalid.
	   Invalid labels are removed.

       •   Volume label in root directory and label in boot sector are
	   different.  Volume label from root directory is copied to boot
	   sector.

       •   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

       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.

       Two different variants of the FAT filesystem are supported.  Standard
       is the FAT12, FAT16 and FAT32 filesystems as defined by Microsoft and
       widely used on hard disks and removable media like USB sticks and SD
       cards.  The other is the legacy Atari variant used on Atari ST.

       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 clusters, where on Atari values 0xfff0–0xfff7 are
       for this purpose (but the standard value is still 0xfff7).

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  Select using the Atari variation of the FAT filesystem if that
	   isn't active already, otherwise select standard FAT filesystem.
	   This is selected by default if mkfs.fat is run on 68k Atari Linux.

       -b  Make read-only boot sector check.

       -c PAGE
	   Use DOS codepage PAGE to decode short file names.  By default
	   codepage 850 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).

       -F NUM
	   Specify FAT table NUM for filesystem access.	 By default value 0 is
	   assumed and then the first uncorrupted FAT table is chosen.
	   Uncorrupted means that FAT table has valid first cluster.  If
	   default value 0 is used and all FAT tables are corrupted then
	   fsck.fat gives up and does not try to repair FAT filesystem.	 If
	   non-zero NUM value is specified then fsck.fat uses FAT table NUM
	   for repairing FAT filesystem.  If FAT table NUM has corrupted first
	   cluster then fsck.fat will repair it.  In any case, if FAT
	   filesystem has more FAT tables then repaired content of chosen FAT
	   table is copied to other FAT tables.	 To repair corrupted first
	   cluster it is required to call fsck.fat with non-zero NUM value.

       -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.

       -S  Consider short (8.3) file names with spaces in the middle to be
	   invalid, like previous versions of this program did.	 While such
	   file names are not forbidden by the FAT specification, and were
	   never treated as errors by Microsoft file system checking tools,
	   many DOS programs are unable to handle files with such names.
	   Using this option can make them accessible to these programs.


	   Short file names which start with a space are considered invalid
	   regardless of this option's setting.


	   Previous versions of this program exceptionally treated EA DATA. SF
	   and WP ROOT. SF as valid short names; using this option does not
	   preserve that exception.

       -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.

       -U  Consider lowercase volume and boot label as invalid and allow only
	   uppercase characters.  Such labels are forbidden by the FAT
	   specification, but they are widely used by Linux tools.  Moreover
	   MS-DOS and Windows systems do not have problems to read them.
	   Therefore volume and boot labels with lowercase characters are by
	   default permitted.

       -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.

       --variant TYPE
	   Create a filesystem of variant TYPE.	 Acceptable values are
	   standard and atari (in any combination of upper/lower case).	 See
	   above under DESCRIPTION for the differences.

       -w  Write changes to disk immediately.

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

       --help
	   Display help message describing usage and options then exit.

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
	   recovered data into files named fsckNNNN.rec in the top level
	   directory of the filesystem.

BUGS
       •   Does not remove entirely empty directories.

       •   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.  Current
       maintainers are Andreas Bombe <aeb@debian.org> and Pali Rohár
       <pali.rohar@gmail.com>.

dosfstools 4.2			  2021-01-31			   FSCK.FAT(8)