fsck.msdos(8) — Linux manual page


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

NAME         top

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

SYNOPSIS         top

       fsck.fat [OPTIONS] DEVICE

DESCRIPTION         top

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

       The following filesystem problems can be corrected (in this

       •   FAT contains invalid cluster numbers.  Cluster is changed to

       •   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

       •   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

       •   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

       •   Start cluster number of a file is invalid.  The file is

       •   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

       •   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         top

       -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

       -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.

           Display help message describing usage and options then exit.

EXIT STATUS         top

       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         top

       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         top

       •   Does not remove entirely empty directories.

       •   Should give more diagnostic messages.

       •   Undeleting files should use a more sophisticated algorithm.

SEE ALSO         top

       fatlabel(8), mkfs.fat(8)

HOMEPAGE         top

       The home for the dosfstools project is its GitHub project page 

AUTHORS         top

       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@

COLOPHON         top

       This page is part of the dosfstools (Tools for making and
       checking MS-DOS FAT filesystems) project.  Information about the
       project can be found at 
       ⟨https://github.com/dosfstools/dosfstools⟩.  If you have a bug
       report for this manual page, see
       ⟨https://github.com/dosfstools/dosfstools/issues⟩.  This page was
       obtained from the project's upstream Git repository
       ⟨https://github.com/dosfstools/dosfstools.git⟩ on 2023-06-23.
       (At that time, the date of the most recent commit that was found
       in the repository was 2023-05-05.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

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

Pages that refer to this page: fsck(8@@e2fsprogs)fsck(8)