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DOSFSCK(8)                   MAINTENANCE COMMANDS                   DOSFSCK(8)

       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  cor-
       rected (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  cor-
              rupt). 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  trun-
       -      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  dis-
       abled 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 dif-
              ferent. 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 clus-
              ters are added to the free disk space except in auto mode (-a).

       -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 incon-

       -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   <werner.almesbergerATlrc.ch>   Extensions
       (FAT32, VFAT) by and current maintainer: Roman Hodek <romanAThodek.net>

Linux                          December 31 1997                     DOSFSCK(8)