dosfsck - check and repair MS-DOS file systems
SYNOPSIS
dosfsck [-aAflrtvVwy] [-d path -d ...] [-u path -u ...]
device
DESCRIPTION
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 adjusted.
- 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 file system check is
restarted after truncation.
- 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.
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.
OPTIONS
-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 used.
-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 is dropped.
-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 clus
ters 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
read.
-w Write changes to disk immediately.
-y Same as -a (automatically repair filesystem) for
compatibility with other fsck tools.
If -a and -r are absent, the file system is only checked,
but not repaired.
EXIT STATUS
0 No recoverable errors have been detected.
1 Recoverable errors have been detected or dosfsck
has discovered an internal inconsistency.
2 Usage error. dosfsck did not access the file sys
tem.
BUGS
Does not create . and .. files where necessary. Does not
remove entirely empty directories. Should give more diag
nostic messages. Undeleting files should use a more
sophisticated algorithm.
AUTHORS
Werner Almesberger <werner.almesberger@lrc.di.epfl.ch>
Extensions (FAT32, VFAT) by and current maintainer: Roman
Hodek <Roman.Hodek@informatik.uni-erlangen.de>
Man(1) output converted with
man2html