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DOSFSCK(8) MAINTENANCE COMMANDS DOSFSCK(8)
dosfsck - check and repair MS-DOS file systems
dosfsck [-aAflrtvVwy] [-d path -d ...] [-u path -u ...] device
dosfsck verifies the consistency of MS-DOS file systems and optionally tries to repair
them. The following file system 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 dropped.
- Files . and .. are non-directories. They can be dropped or renamed.
- Directories . and .. in root directory. They are dropped.
- Bad file names. They can be renamed.
- Duplicate directory entries. They can be dropped 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
- 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 trun-
- Two or more files share the same cluster(s). All but one of the files are trun-
cated. If the file being truncated is a directory file that has already been read,
the file system check is restarted after truncation.
- File's cluster chain is shorter than indicated by the size fields. The file is
- 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
When dosfsck checks a file system, it accumulates all changes in memory and performs them
only after all checks are complete. This can be disabled with the -w option.
-a Automatically repair the file system. No user intervention is necessary. Whenever
there is more than one method to solve a problem, the least destructive approach is
-A Use Atari variation of the MS-DOS filesystem. This is default if dosfsck 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).
-d Drop the specified file. If more that one file with that name exists, the first one
-f Salvage unused cluster chains to files. By default, unused clusters are added to
the free disk space except in auto mode (-a).
-l List path names of files being processed.
-r Interactively repair the file system. The user is asked for advice whenever there
is more than one approach to fix an inconsistency. This is the default behaviour.
-t Mark unreadable clusters as bad.
-u Try to undelete the specified file. dosfsck tries to allocate a chain of contiguous
unallocated clusters beginning with the start cluster of the undeleted file.
-v Verbose mode. Generates slightly more output.
-V Perform a verification pass. The file system 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.
-w Write changes to disk immediately.
-y Same as -a (automatically repair filesystem) for compatibility with other fsck
If -a and -r are absent, the file system is only checked, but not repaired.
0 No recoverable errors have been detected.
1 Recoverable errors have been detected or dosfsck has discovered an internal incon-
2 Usage error. dosfsck did not access the file system.
Does not create . and .. files where necessary. Does not remove entirely empty directo-
ries. Should give more diagnostic messages. Undeleting files should use a more sophisti-
Werner Almesberger <email@example.com> Extensions (FAT32, VFAT) by and
current maintainer: Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de>
Linux December 31 1997 DOSFSCK(8)
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