XBACKUP(F) UNIX System V
Name
xbackup - XENIX incremental dump tape format
Description
The xbackup and xrestore 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_TAPE 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.
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
xbackup(ADM), xrestore(ADM), filesystem(F)
Value Added
xbackup is an extension of AT&T System V provided by the
Santa Cruz Operation.
(printed 2/15/90) XBACKUP(F)