ISO Image dd To DVD+RW

[Frank Mitchell]

Hi:

Latest issue of Linux Format Mag gives you a DVD ISO Image for FreeBSD v8.0,
which I happen to be interested in. I was also looking for an interesting use
for my DVD+RW disks. I read somewhere you could "dd" straight from an ISO
Image file to DVD+RW, though I couldn't remember where.

Previously I thought you could put an Ext2 Filesystem on DVD+RW, which turned
out to be wrong. It worked the first time I tried, but not the second. But
this experiment with "dd" worked, though I'm still unsure about how to use
some of the options properly. Basically (under Linux) I put:

dd if=FreeBSD-8.iso of=/dev/sr1 ibs=512 obs=32768 conv=sync

And my DVD+RW wrote okay, showing:

3986344+0 Records In
62286+1 Records Out

Note that DVDs use 2048-byte Sectors like CDs, but they're handled in
Error-Correcting Super-Blocks of 16. DVD+RW can write individual Sectors, but
only by updating the entire Super-Block. My first attempt tried writing with a
BlockSize of 2048, whereupon Drive /dev/sr1 sat there winding the disk back
and forth, presumably writing every Super-Block 16 times over. With a total
BlockSize of 32768 things went alot more smoothly. The 62286+1 Records Out
are Super-Blocks with an extra one partially written. The original 3986344
Records were 512-byte Disk Blocks, which make a whole number of 2048-byte DVD
Sectors, but not Super-Blocks.

Then I wrote it back to a file so I could check the result using diff:

dd if=/dev/sr1 of=CHECK.ISO bs=2048 count=996586 conv=notrunc

Here it's okay to read the DVD as 2048-byte Sectors, because they're
individually addressable. You need the count to stop the entire DVD getting
imaged, all 4.7 GB, which happened the first time I tried. And of course it's
the count of 2048-byte Sectors, which is 3986344/4.

CHECK.ISO was identical to the original Iso Image, and I was able to use the
DVD+RW to install FreeBSD v8.0. Which left me with the same Xorg
Configuration problems as FreeBSD v7.2, but that's another story...

Faictz Ce Que Vouldras: Frank Mitchell

[Oliver Fromme]

Frank Mitchell <> wrote:
> Latest issue of Linux Format Mag gives you a DVD ISO Image for FreeBSD v8.0,
> which I happen to be interested in. I was also looking for an interesting use
> for my DVD+RW disks. I read somewhere you could "dd" straight from an ISO
> Image file to DVD+RW, though I couldn't remember where.

Don't know about Linux, but on FreeBSD you can use the growisofs tool
from the "dvd+rw" tools collection (ports/sysutils/dvd+rw-tools).
The syntax is simple: growisofs -dvd-compat -Z /dev/cd0=dvdimage.iso
(/dev/cd0 is my dvd drive.) I think you can also use the burncd
tool that is part of FreeBSD's base system, but I haven't tried to
do that. growisofs works perfectly fine for me (it also handles
double-layer media (8.5 GB) correctly, BTW).

You cannot use dd for that purpose because dd doesn't have special
knowledge about the recording process, e.g. it doesn't know how to
determine the laser power, it doesn't know how to enable burn-proof,
it doesn't know how to fixate a CD or DVD, i.e. the session won't
be closed properly, and so on. That's why a special-purpose tool
is better suited to handle recording of CD and DVD media.

Best regards
Oliver

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[Frank Mitchell]

Hmm:

I reckon you need to use Formatted Media, which DVD+RW must be. It's Randomly
Addressable, so you don't need to Close Session like on a Read-Only Disk.
Buffer Underruns are supposed to be irrelevant using DVD+. And the Drive
itself can calibrate the Optical Power from the Disk itself. I know I read
about this somewhere, and the article in question was saying you could
archive tar files this way. Anybody got any further info?

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[Oliver Fromme]

Frank Mitchell wrote:
> I reckon you need to use Formatted Media, which DVD+RW must be.

I don't think you need to format it if you're just going to
write an ISO image to it.

(Personally I avoid DVD+/-RW, so I can't tell for sure, but
I guess it shouldn't be much different from CD-RW as far as
writing an ISO image goes.)

Best regards
Oliver

--
Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M.
Handelsregister: Registergericht Muenchen, HRA 74606, Gesch�ftsfuehrung:
secnetix Verwaltungsgesellsch. mbH, Handelsregister: Registergericht M�n-
chen, HRB 125758, Gesch�ftsf�hrer: Maik Bachmann, Olaf Erb, Ralf Gebhart

FreeBSD-Dienstleistungen, -Produkte und mehr: http://www.secnetix.de/bsd

"File names are infinite in length, where infinity is set to 255 characters."
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