dosfsck



DOSFSCK(8)                   MAINTENANCE COMMANDS                   DOSFSCK(8)




NAME

       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  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 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.


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  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.

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


BUGS

       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.


AUTHORS

       Werner   Almesberger   <werner.almesberger@lrc.di.epfl.ch>   Extensions
       (FAT32,   VFAT)   by    and    current    maintainer:    Roman    Hodek
       <Roman.Hodek@informatik.uni-erlangen.de>



Linux                          December 31 1997                     DOSFSCK(8)

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