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       dosfsck - check and repair MS-DOS file systems


       dosfsck [-aAflnrtvVwy] [-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
       -      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
       -      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.


       -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

       -l     List path names of files being processed.

       -n     No-operation mode: non-interactively check for errors, but don’t
              write anything to the filesystem.

       -r     Interactively  repair  the  file  system.  The user is asked for
              advice whenever there is  more  than  one  approach  to  fix  an

       -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 tools.

       If -a and -r are absent, the file  system  is  only  checked,  but  not


       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 system.


       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.


       Werner   Almesberger   <>   Extensions
       (FAT32, VFAT) by and current maintainer: Roman Hodek <>