dosfsck

NAME

       dosfsck - check and repair MS-DOS file systems

SYNOPSIS

       dosfsck [-aflrtvVw] [-dpath-d...]  [-upath-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.
       -      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.

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.

       -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.

       -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.

       -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 mod-
              ifications that have to be scanned  for  each  disk
              read.

       -w     Write changes to disk immediately.

       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.

AUTHOR

       Werner Almesberger <almesber@bernina.ethz.ch>