.th DUMP V 2/11/75
.sh NAME
dump \*- incremental dump tape format
.sh DESCRIPTION
The
.it dump
and
.it restor
commands are used to write
and read incremental dump magnetic tapes.
.s3
The dump tape consists of
blocks of 512-bytes each.
The first block has the following structure.
.s3
.nf
struct {
	int	isize;
	int	fsize;
	int	date[2];
	int	ddate[2];
	int	tsize;
};
.s3
.fi
.it Isize,
and
.it fsize
are the corresponding values from the
super block of the dumped file system.
(See file system (V).)
.it Date
is the date of the dump.
.it Ddate
is the incremental dump date.
The incremental dump contains
all files modified
between
.it ddate
and
.it date.
.it Tsize
is the number of blocks per
reel.
This block checksums to the octal value
031415.
.s3
Next there are enough whole tape blocks
to contain one word per file of the dumped file system.
This is
.it isize
divided by 16 rounded to the next higher integer.
The first word corresponds to i-node 1, the second to i-node 2, and
so forth.
If a word is zero, then the corresponding file
exists, but was not dumped.
(Was not modified after
.it ddate)
If the word is \*-1,
the file does not exist.
Other values for the word
indicate that the file was dumped and the value
is one more than the number of blocks it contains.
.s3
The rest of the tape
contains for each dumped file
a header block and the data blocks
from the file.
The header contains an exact copy of the
i-node
(see file system (V))
and also checksums to
031415.
The next-to-last word of the block contains the tape block number,
to aid in (unimplemented)
recovery after tape errors.
The number of data blocks per file is
directly specified by the control word for the file
and indirectly specified by the size in the i-node.
If these numbers differ,
the file was dumped with a `phase error'.
.sh "SEE ALSO"
dump (VIII), restor (VIII), file system(V)