fsck.fat - check and repair MS-DOS FAT filesystems
fsck.fat [OPTIONS] DEVICE
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).
- -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.
- 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.
- 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.
- Does not remove entirely empty directories.
- Should give more diagnostic messages.
- Undeleting files should use a more sophisticated algorithm.