BACKUP(F) XENIX System V BACKUP(F)
Name
backup - Incremental dump tape format.
Description
The backup and restore commands are used to write and read
incremental dump magnetic tapes.
The backup tape consists of a header record, some bit mask
records, a group of records describing file system
directories, a group of records describing file system
files, and some records describing a second bit mask.
The header record and the first record of each description
have the format described by the structure included by:
#include <dumprestor.h>
Fields in the dumprestor structure are described below.
NTREC is the number of 512 byte blocks in a physical tape
record. MLEN is the number of bits in a bit map word. MSIZ
is the number of bit map words.
The TS_ entries are used in the c_type field to indicate
what sort of header this is. The types and their meanings
are as follows:
TS_TYPE Tape volume label.
TS_INODE A file or directory follows. The c_dinode field
is a copy of the disk inode and contains bits
telling what sort of file this is.
TS_BITS A bit mask follows. This bit mask has one bit
for each inode that was backed up.
TS_ADDR A subblock to a file (TS_INODE). See the
description of c_count below.
TS_END End of tape record.
TS_CLRI A bit mask follows. This bit mask contains one
bit for all inodes that were empty on the file
system when backed up.
MAGIC All header blocks have this number in c_magic.
CHECKSUM Header blocks checksum to this value.
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BACKUP(F) XENIX System V BACKUP(F)
The fields of the header structure are as follows:
c_type The type of the header.
c_date The date the backup was taken.
c_ddate The date the file system was backed up.
c_volume The current volume number of the backup.
c_tapea The current block number of this record. This
is counting 512 byte blocks.
c_inumber The number of the inode being backed up if this
is of type TS_INODE.
c_magic This contains the value MAGIC above, truncated
as needed.
c_checksum This contains whatever value is needed to make
the block sum to CHECKSUM.
c_dinode This is a copy of the inode as it appears on
the file system.
c_count The following count of characters describes the
file. A character is zero if the block
associated with that character was not present
on the file system; otherwise, the character is
nonzero. If the block was not present on the
file system no block was backed up and it is
replaced as a hole in the file. If there is
not sufficient space in this block to describe
all of the blocks in a file, TS_ADDR blocks
will be scattered through the file, each one
picking up where the last left off.
c_addr This is the array of characters that is used as
described above.
Each volume except the last ends with a tapemark (read as an
end of file). The last volume ends with a TS_END block and
then the tapemark.
The structure idates describes an entry of the file where
backup history is kept.
See Also
backup(C), restore(C), filesystem(F)
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