Ausam/doc/man/man8/chk.8

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.th CHK VIII 8/15/78
.sh NAME
chk \*- file system storage consistency check
.sh SYNOPSIS
.bd chk
[\c
.bd \*-a\c
][\c
.bd \*-b\c
list][\c
.bd \*-i\c
list][\c
.bd \*-q\c
][\c
.bd \*-s\c
][\c
.bd \*-v\c
][\c
.bd \*-x\c
][filesystems]
.sh DESCRIPTION
.it Chk
examines the given filesystems, making various consistency checks.
It replaces, and is considerably faster than, the older
.it dcheck,
.it icheck,
and
.it ncheck.
.s3
.it Chk
builds three bitmaps of the filesystem being checked.
One simply records used blocks, and is used to check for
.it dups
(blocks that appear in more than one file,
and/or in the free\-list), and
.it missings
(blocks not accounted for
elsewhere).
Another bitmap records indirect blocks, so that these may be
read in order (disk heads move in one direction).
The third bitmap records directory blocks, so that these
may be similarly read in order
to find how many references there are
to every file.
This is compared with the inode link\-count for each file,
and any discrepancies are reported.
A check is also made that every part of the directory tree can
be reached from the root directory (no
.it orphans).
.s3
The options, which may appear in any order (but before the filesystems),
are:
.s3
.lp +10 8
\fI-a\fB	This option modifies the output of the \fI-i\fB option
(below), to print out even `.' and `..' names.
.s3
.lp +10 8
\fI-b\fB list	The filesystem is searched for the blocks in the list.
The i\-numbers of files containing those blocks are printed out.
.s3
.lp +10 8
\fI-i\fB list	The filesystem is searched for the i\-numbers in the list.
The path\-names of files matching those i\-numbers are printed out.
Names `.' and `..' are suppressed (see \fI-a\fB options above).
.s3
.lp +10 8
\fI-q\fB	Quiet option. Only the filesystem name is printed out
(if there are no errors).
.s3
.lp +10 8
\fI-s\fB	Salvage option. This causes
.it chk
to ignore the actual free list and reconstruct a new one by rewriting
the super\-block of the filesystem.
It is used to recover
.it missings,
and to correct
.it dups
in the free\-list.
.s3
.lp +10 8
\fI-v\fB	Verbose option.
.it Chk
normally prints out only the number of free inodes and blocks.
This option generates a report of
.s3
.in +10
.ti -5
the actual
.it fsize
and
.it isize
(from the superblock);
.ti -5
the number of used blocks;
.ti -5
the number of special files (block and char);
.ti -5
the number of ordinary files;
.ti -5
the number of large files (including large directories and huge files);
and the number of huge files;
.ti -5
the number of directories;
.ti -5
the number of indirect blocks; and the number of double indirect blocks
of huge files;
.ti -5
the high-water mark block number;
.ti -5
the number of free inodes; and
.ti -5
the number of free blocks.
.s3
.lp +10 8
\fI-x\fB	This option causes
.it chk
to print out the i\-numbers of all special\-files on the filesystem.
.s3
.i0
.dt
Because of the way
.it chk
stores indirect block numbers in a bitmap, the inodes of
files containing
.it bad
(i.e. out of range) or
.it dup
blocks are not always known.
An extra pass is made at the end to find these i\-numbers,
which are added to the list of i\-numbers to be matched
with path\-names.
.s3
If the \fI-s\fB option (above) is used, the filesystem should
be dismounted. If this is not possible (because it is the root
filesystem) the system must be quiescent, and must be rebooted
immediately afterwards so that the old, bad in\-core copy
of the super\-block will not continue to be used.
.s3
If the file system is not specified,
a set of default file systems
is checked.
The exit status from
.it chk
has the 0200 bit set if it considers the filesystem not fit
to run on.
The 01 bit is set for core\-errors (lack of); 02 for open\-errors;
and 04 for non\-fatal disk errors.
.s3
.it Chk
is faster if the raw version of the special file is used,
since it reads the i-list many blocks at a time.
.sh "SEE ALSO"
fs (V), clri (VIII), ipatch (VIII)
.sh DIAGNOSTICS
If a read error is encountered, the block number is printed out and
.it chk
exits.
For duplicate and bad blocks, the block number, reason, and type
are printed out. If the i\-number is known, it is also printed out,
otherwise an extra pass is made at the end to find it.
Illegal values for
.it nfree
in the super\-block generate an appropriate message.
If a file turns up for which the link\-count and the number
of directory entries disagree, the relevant facts are reported.
Allocated files which have zero link-count and no entries are also
listed (possibly pipes if on the root filesystem).
.sh AUTHOR
Original from Vrije Universiteit, Amsterdam.
Modified by Kevin Hill (University of NSW).
.sh BUGS
Since
.it chk
makes numerous passes of the filesystem,
extraneous diagnostics
may be produced if applied to mounted file systems.
.br
It believes even preposterous values for
.it fsize
and
.it isize
(in the super-block), and
consequently can get core images.
As a result of the algorithm used,
.it chk
can not differentiate between data blocks
for large and huge files in its diagnostic output.