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>


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