icheck.8

UNIX v6源代码 这几乎是最经典的unix版本 unix操作系统设计和莱昂氏unix源代码分析都是用的该版

.th ICHECK VIII 2/9/75
.sh NAME
icheck \*- file system storage consistency check
.sh SYNOPSIS
.bd icheck
[
.bd \*-s
]  [
.bd \*-b
numbers ]
[ filesystem ]
.sh DESCRIPTION
.it 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
.it icheck
includes a report of
.s3
.lp +4 0
The number of blocks missing; i.e. not in any file
nor in the free list,
.lp +4 0
The number of special files,
.lp +4 0
The total number of files,
.lp +4 0
The number of large and huge files,
.lp +4 0
The number of directories,
.lp +4 0
The number of indirect blocks,
and the number of double-indirect blocks in huge files,
.lp +4 0
The number of blocks used in files,
.lp +4 0
The number of free blocks.
.s3
.i0
The
.bd \*-s
flag causes
.it 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 and that
it is rebooted immediately 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
.bd \*-s
flag
causes the normal output reports to be suppressed.
.s3
Following the
.bd \-b
flag is a list of block numbers;
whenever any of the named blocks turns up in a file,
a diagnostic is produced.
.s3
.it Icheck
is faster if the raw version of the special file is used,
since it reads the i-list many blocks at a time.
.sh FILES
Currently, /dev/rrk2
and /dev/rrp0
are the default file systems.
.sh "SEE ALSO"
dcheck (VIII), ncheck (VIII),
fs (V), clri (VIII), restor(VIII)
.sh DIAGNOSTICS
For duplicate blocks
and bad blocks (which lie outside the file system)
.it 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
.it icheck
considers it to contain 0.
``Bad freeblock'' means that
a block number outside the available space was encountered in the free list.
``\fIn\fR dups in free''
means that \fIn\fR blocks were found in the free list which
duplicate blocks either in some file or in the earlier part of the free list.
.sh BUGS
Since
.it icheck
is inherently two-pass in nature, extraneous diagnostics
may be produced if applied to active file systems.
.br
It believes even preposterous super-blocks and
consequently can get core images.