NAME
dump - incremental dump tape format
DESCRIPTION
The dump and restor commands are used to write and read
incremental dump magnetic tapes.
The dump tape consists of blocks of 512-bytes each. The
first block has the following structure.
struct {
int isize;
int fsize;
int date[2];
int ddate[2];
int tsize;
};
Isize, and fsize are the corresponding values from the super
block of the dumped file system. (See file system (V).)
Date is the date of the dump. Ddate is the incremental dump
date. The incremental dump contains all files modified
between ddate and date. Tsize is the number of blocks per
reel. This block checksums to the octal value 031415.
Next there are enough whole tape blocks to contain one word
per file of the dumped file system. This is 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 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.
The rest of the tape contains for each dumped file a header
block and the data blocks from the file. The header con-
tains 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 (unimple-
mented) 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'.
SEE ALSO
dump (VIII), restor (VIII), file system(V)
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