- check and repair MS-DOS filesystems
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
- File's cluster chain contains a loop. The loop is
- 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
- Directories . and .. in root directory. They are
- Bad filenames. They can be renamed.
- Duplicate directory entries. They can be deleted or
- Directories with non-zero size field. Size is set to
- 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
- File contains bad or free clusters. The file is
- 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
- 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
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
- 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.
- 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 format. 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).
- Make read-only boot sector check.
- -c PAGE
- Use DOS codepage PAGE to decode short file names. By
default codepage 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
- Salvage unused cluster chains to files. By default, unused
clusters are added to the free disk space except in auto mode (
- List path names of files being processed.
- No-operation mode: non-interactively check for errors, but
don't write anything to the filesystem.
- Same as -a, for compatibility with other *fsck.
- 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
- 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
- Verbose mode. Generates slightly more output.
- 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.
- Write changes to disk immediately.
- Same as -a (automatically repair filesystem) for
compatibility with other fsck tools.
- No recoverable errors have been detected.
- Recoverable errors have been detected or fsck.fat
has discovered an internal inconsistency.
- Usage error. fsck.fat did not access the
- 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 create . and .. files where necessary. Does not remove entirely empty
directories. Should give more diagnostic messages. Undeleting files should use
a more sophisticated algorithm.
The home for the dosfstools
project is its
were written by
and others. The current maintainer is