ICHECK(8) System Manager's Manual ICHECK(8)
icheck - file system storage consistency check
/usr/etc/icheck [ -s ] -b numbers ] [ filesystem ]
Note: icheck has been superseded for normal consistency checking by
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 sys-
tem. The normal output of icheck includes a report of
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; that is, not in any file nor in
the free list.
With the -s option icheck ignores the actual free list and reconstructs
a new one by rewriting the superblock 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 salvaged) care should be
taken that the system is quiescent and that it is rebooted immediately
afterwards so that the old, bad in-core copy of the superblock will not
continue to be used. Notice also that the words in the superblock
which indicate the size of the free list and of the i-list are
believed. If the superblock has been curdled these words will have to
be patched. The -s option suppresses the normal output reports.
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.
fs(5), clri(8), dcheck(8), fsck(8), ncheck(8)
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 encountered, the block number of the bad
block is printed and icheck considers it to contain 0.
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
Since icheck is inherently two-pass in nature, extraneous diagnostics
may be produced if applied to active file systems.
It believes even preposterous superblocks and consequently can get core
The system should be fixed so that the reboot after fixing the root
file system is not necessary.
9 September 1987 ICHECK(8)