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DOSFSCK(8)		     MAINTENANCE COMMANDS		    DOSFSCK(8)



NAME
       dosfsck - check and repair MS-DOS file systems

SYNOPSIS
       dosfsck [-aAflnrtvVwy] [-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.

       -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-
	      sistency.

       -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.net>



Linux			       December 31 1997			    DOSFSCK(8)
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