Provided by: dosfstools_4.2-1build3_amd64 
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⟩.