ICHECK(8) ICHECK(8)
NAME
icheck, dcheck, ncheck - file system consistency check
SYNOPSIS
/etc/icheck [ -B ] [ -s ] [ -b numbers ] [ filesystem ]
/etc/dcheck [ -B ] [ -i numbers ] [ filesystem ]
/etc/ncheck [ -B ] [ -i numbers ] [ -a ] [ -s ] [ filesystem
]
DESCRIPTION
These programs perform consistency checks on file systems.
For normal file system maintenance, see fsck(8).
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 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 direc-
tory 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 salvaged) care should be taken
that the system is quiescent. 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 or the free list,
a diagnostic is produced.
Dcheck reads the directories in a file system and compares
the link-count in each i-node with the number of directory
ICHECK(8) ICHECK(8)
entries by which it is referenced. The -i flag is followed
by a list of i-numbers; when one of those i-numbers turns up
in a directory, the number, the i-number of the directory,
and the name of the entry are reported.
Ncheck generates a pathname vs. i-number list of all files
in a file system. Names of directory files are followed by
`/.'. The -i option reduces the report to only those files
whose i-numbers follow. The -a option allows printing of
the names `.' and `..', which are ordinarily suppressed.
The -s option reduces the report to special files and files
with set-user-ID mode; it is intended to discover concealed
violations of security policy. The report is in no useful
order, and probably should be sorted.
These programs are faster if the raw version of the special
file is used, since they read the i-list many blocks at a
time.
If filesystem is a special file, the minor device number is
checked to distinguish between regular and bitmapped file
systems. If the filesystem resides in a regular file, it is
assumed to be a regular file system unless the -B option is
used.
FILES
Default file systems vary with installation.
SEE ALSO
fsck(8), filsys(5), clri(8)
DIAGNOSTICS
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 encoun-
tered 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.
When a file turns up for which the link-count and the number
of directory entries disagree, dcheck reports the relevant
facts. Allocated files which have 0 link-count and no
entries are also listed. The only dangerous situation
occurs when there are more entries than links; if entries
are removed, so the link-count drops to 0, the remaining
entries point to thin air. They should be removed. When
there are more links than entries, or there is an allocated
file with neither links nor entries, some disk space may be
lost but the situation will not degenerate.
ICHECK(8) ICHECK(8)
When the filesystem structure is improper, ncheck prints
`??' to denote the `parent' of a parentless file. A path-
name beginning with `...' denotes a loop.
BUGS
Since these commands are inherently two-pass in nature,
extraneous diagnostics may be produced if applied to active
file systems.
They believe even preposterous super-blocks and consequently
can get core images.