Re: DVD-R as backup medium: growisofs + udftools

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

Joerg Schilling:
> > It is _impossible_ to do correct backups without additional disk space.
Giuseppe Corbelli:
> You say it is necessary to store star archives on a filesystem prior
> to backup?

It is possible to write archives as sessions
directly to multi-session media: DVD-R, DVD+R,
DVD-RW, CD-R, CD-RW.
As long as one knows the start addresses it
is easy to read the archives by help of dd.
This works for afio as well as for star.

Try for example:
  find . | \
  afio -oZ - | \
  cdrskin -v dev=/dev/sr0 -multi -

The writer drive should be able to tell a
table of content:
  cdrskin -v dev=/dev/sr0 -toc

With a 4 session DVD+R it should report
something like:
  ...
  cdrskin: status 3 BURN_DISC_APPENDABLE "There is an incomplete disc in the drive"
  ...
  Current: DVD+R
  ...
  first: 1 last 4
  track:   1 lba:         0 (        0) 00:02:00 adr: 1 control: 4 mode: 1
  track:   2 lba:     66112 (   264448) 14:43:37 adr: 1 control: 4 mode: 1
  track:   3 lba:     87744 (   350976) 19:31:69 adr: 1 control: 4 mode: 1
  track:   4 lba:   1663056 (  6652224) 369:36:06 adr: 1 control: 4 mode: 1
  track:lout lba:   1682640 (  6730560) 373:57:15 adr: 1 control: 4 mode: -1

The lba values 0, 66112, 87744, 1663056 tell the
start addresses in 2048 byte blocks.
Like:
  lba=66112
  dd if=/dev/sr0 bs=2048 skip=$lba | afio -tv -

One problem is that my DVD-ROM drive does not tell
about all DVD tracks but at most issues a fake table
of content with an initial pseudo-session and the
last session.
So one should memorize the start addresses after burning.


Have a nice day :)

Thomas