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Unix Version 7 - man page for icheck (v7 section 1M)

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ICHECK(1M)									       ICHECK(1M)

       icheck - file system storage consistency check

       icheck [ -s ]  [ -b numbers ] [ filesystem ]

       Icheck  examines a file system, builds a bit map of used blocks, and compares this bit map
       against the free list maintained on the file system.  If the file system is not specified,
       a  set  of default file systems is checked.  The normal output of icheck includes a report

	      The total number of files and the numbers of regular, directory, block special  and
	      character special files.

	      The  total number of blocks in use and the numbers of single-, double-, and triple-
	      indirect blocks and directory blocks.

	      The number of free blocks.

	      The number of blocks missing; i.e. not in any file nor in the free list.

       The -s option causes icheck to ignore the actual free list and reconstruct a  new  one  by
       rewriting  the super-block of the file system.  The file system should be dismounted while
       this is done; if this is not possible (for example if the root file system has to be  sal-
       vaged)  care  should be taken that the system is quiescent and that it is rebooted immedi-
       ately afterwards so that the old, bad in-core copy of the super-block will not continue to
       be  used.   Notice  also  that the words in the super-block which indicate the size of the
       free list and of the i-list are believed.  If the super-block has been curdled these words
       will have to be patched.  The -s option causes the normal output reports to be suppressed.

       Following the -b option is a list of block numbers; whenever any of the named blocks turns
       up in a file, a diagnostic is produced.

       Icheck is faster if the raw version of the special file is used, since it reads the i-list
       many blocks at a time.

       Default file systems vary with installation.

       dcheck(1), ncheck(1), filsys(5), clri(1)

       For  duplicate  blocks and bad blocks (which lie outside the file system) icheck announces
       the difficulty, the i-number, and the kind of block involved.  If a read error is  encoun-
       tered,  the block number of the bad block is printed and icheck considers it to contain 0.
       `Bad freeblock' means that a block number outside the available space was  encountered  in
       the  free  list.   `n  dups in free' means that n blocks were found in the free list which
       duplicate blocks either in some file or in the earlier part of the free list.

       Since icheck is inherently two-pass in nature, extraneous diagnostics may be  produced  if
       applied to active file systems.
       It believes even preposterous super-blocks and consequently can get core images.

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