DOSFSCK(8)                   MAINTENANCE COMMANDS
DOSFSCK(8)



NNAAMMEE
       dosfsck - check and repair MS-DOS file systems

SSYYNNOOPPSSIISS
       ddoossffsscckk
       [--aaAAffllnnrrttvvVVwwyy] [--dd
       _p_a_t_h --dd _._._.]  [--uu _p_a_t_h
       --uu _._._.]  _d_e_v_i_c_e

DDEESSCCRRIIPPTTIIOONN
       ddoossffsscckk  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
              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  trun‐
              cated.
       -      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 ddoossffsscckk 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w option.

OOPPTTIIOONNSS
       --a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A     Use Atari variation of the MS-DOS
       filesystem. This is default if
              ddoossffsscckk 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d     Drop the specified file. If more that one
       file  with  that  name
              exists, the first one is dropped.

       --ff     Salvage unused cluster chains to files. By
       default, unused clus‐
              ters are added to the free disk space except
              in auto mode (--aa).

       --ll     List path names of files being processed.

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

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

       --tt     Mark unreadable clusters as bad.

       --uu     Try  to undelete the specified
       file. ddoossffsscckk tries to allocate a
              chain of contiguous  unallocated  clusters
              beginning  with  the start cluster of the
              undeleted file.

       --vv     Verbose mode. Generates slightly more output.

       --V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w     Write changes to disk immediately.

       --yy     Same  as  --aa (automatically repair
       filesystem) for compatibility
              with other fsck tools.

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

EEXXIITT SSTTAATTUUSS
       0      No recoverable errors have been detected.

       1      Recoverable  errors have been detected or
       ddoossffsscckk has discovered
              an internal inconsistency.

       2      Usage error. ddoossffsscckk did not
       access the file system.

BBUUGGSS
       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.

AAUUTTHHOORRSS
       Werner   Almesberger
       <werner.almesberger@lrc.di.epfl.ch>   Extensions
       (FAT32, VFAT) by and current maintainer: Roman Hodek
       <roman@hodek.net>



Linux                          December 31 1997
DOSFSCK(8)
