xbackup(F)

Format

Description

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 dumprestor structure defined in the file /usr/include/dumprestor.h.

The members of the header structure are as follows:

c_type

The header type.

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 c_type is of type TS_INODE.

c_magic

This contains the value MAGIC, 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.

The TS_ entries are used in the c_type field to indicate the header type. 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 describing 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.

Other quantities defined in dumprestor.h are:

CHECKSUM

Header blocks checksum to this value.

MAGIC

All header blocks have this number in c_magic.

MLEN

The number of bits in a bit map word.

MSIZ

The number of bit map words.

NTREC

The number of 512-byte blocks in a physical tape record.

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.

Files

/usr/include/dumprestor.h

header file defining the xbackup format

See also

Standards conformance