term% cat index.txt ICHECK(8) System Manager's Manual 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 sys‐
tem. If the file system is not specified, a set of default file sys‐
tems 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 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 recon‐
struct 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 sup‐
pressed.
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 pro‐
duced.
Dcheck reads the directories in a file system and compares the link-
count in each i-node with the number of directory 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-num‐
ber 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 vio‐
lations 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 encountered, 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 ear‐
lier part of the free list.
When a file turns up for which the link-count and the number of direc‐
tory 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 en‐
tries 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 de‐
generate.
When the filesystem structure is improper, ncheck prints `??' to denote
the `parent' of a parentless file. A pathname beginning with `...' de‐
notes a loop.
BUGS
Since these commands are inherently two-pass in nature, extraneous di‐
agnostics may be produced if applied to active file systems.
They believe even preposterous super-blocks and consequently can get
core images.
ICHECK(8)