dosfsck man page on aLinux

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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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