27 Tbackup floppy format

Contents of this section

Here is how tbackup stores an archive on floppies. This information may be useful in some cases.

Tbackup uses a normal MS-DOS file structure on its floppies. This has several advantages:

Each tbackup floppy contains a file called DESCR2K. It contains a description of the backup set the floppy belongs to and some parameters that are used when restoring the archive. All floppies in a backup set have the same DESCR2K file, which is either 2 Kb or 1.5 Kb big. Here is an example:

Full backup of directory set mystuff.
(Filenames in archive relative to /)
Made with tbackup (V0.8)
by root@noodle.nl, on Sun Apr 17 14:06:14  1994
---
export dea_choosemethod=set
export dea_setname=mystuff
export dea_packhome=/
export dea_level=f
export dea_backupdate=041714051994
export dea_unpackmethod=afio
export dea_readmethod=floppy
export pre_mdens=h
export pre_eccmethod=blexta08
export pre_psize=1381376
export dea_indexfilename=/root/idx/mystuff.idx.5
<<<
This is a filler string to get a 1.5k file.................
This is a filler string to get a 1.5k file.................
[etc.]
In general you can use a command like
mtype b:descr2k |head
to see the relevant part.

Tbackup puts files called PARTAA.001, PARTAB.002, PARTAC.003, etc. on the consecutive floppies of the backup set. These files hold the real archive information, if you put them all together you get an afio (or tar) format archive file.

The error correcting codes for each floppy are in files called ECORAA.001, ECORAB.002, etc. The codes are made with the blexta (Block Level EXor Trace Assembly) algorithm, see the /usr/lib/tbackup/bin/ecor.c source code for more information.

On the last disk of the backup set, a file called PART} is written indicate the end of the set.

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