[ILUG] Backing up a CD

[Rik Dunphy]

Kenn Humborg wrote:
> 
> > > Well, first of all nothing can just take the "raw binary data" off a CD.
> [...snip...]
> > It should be possible to read raw binary data. Red/Yellow book is what you
> > called it, a format. It should be (and as far as I know is) possible to
> > read the raw data from the disk to create a binary image of the disk, by
> > circumventing the formats.
> 
> It's _possible_, but not as straightforward as you imagine.  You
> mention that you want to do
> 
> dd if=/dev/cdrom of=imagefile
> 
> for any type of CD format and have it work.  What about multiple tracks?
> It's a bit like reading from tapes.  You can copy two files onto a tape,
> for example:
> 
>    mt rewind
>    dd if=file1 of=/dev/nst0
>    dd if=file2 of=/dev/nst0
> 
> But there is no way (short of special custom data recovery apps) to get
> a single file that describes this tape.  In other words:
> 
>    mt rewind
>    dd if=/dev/nst0 of=some-file
> 
> will give you an exact copy of file1, not file1+file2.  There is additional
> 'metadata' on the tape that's not accessible outside the tape drive itself.
>

Didn't think it would be easy, but thought it should be possible. I'm only
looking for hints on how to go about doing this!
 
<snip>
> 
> The file that CD Maker Pro is probably a proprietary format.  I don't know
> of any standard format for storing anything fancier than a filesystem
> image (eg .iso).

Don't know if it is or isn't, but would assume that it is their own format.
 
> For example, Adaptec CD Creator (which I've used - I haven't used CD Maker
> Pro) creates 'image' files in a format they call .CIF.  It's proprietary.
> 
> The problem is not "NT can do this, Linux can't", it's "nobody's written
> the software and designed an open file format" for doing this.

I never said that! I draw the reference between the two in light of my
problem. I want to copy a CD-Extra. This is very easy with CD Maker Pro
under Windows, but very complicated with Linux Tools. Maybe I am doing
things wrong, but I have followed the CD-Writing Howto and all relevant
docs for the tools.

The most annoying problem is with the audio tracks. When I play an audio cd
the player gets the info for the disk and gives me the track information,
title etc, quite easily. But when I copy using xcdroast this information is
lost. I assume this is to do with the CD-Text option on the CD. According
to xcdroast my CDRW doesn't support this, yet it copies perfectly in CD
Maker Pro.
 
<snip>
> >
> > What I meant was that dd will only copy data from the drive in what ever
> > format it's in (iso9660, FAT, NTFS, ADFS etc.). In Solaris there are two
> > types of disk device, one for normal disk operation /dev/sdX and one for
> > raw operations /dev/rsdX.
> >
> > If there is a raw disk driver for Linux then dd should be able to
> > do what I
> > want, but I don't know if one exists.
> 
> >From what I've seen, raw disk I/O in Linux means something else.
> It's something like bypassing the kernel's buffer cache and
> taking a more direct route to the disk.

This is what I meant. By bypassing the kernel the raw data can be read from
the CD without any format overheads. This I think is something like CD
Maker Pro or CD Clone on windows do, allowing perfect 1:1 copies. My
question is what is the raw device driver, and how do I then write the raw
file back to a CD-R?
 
> And the actual on-disk format of the audio data on CDs doesn't lend
> itself to being read by a kernel driver.  This has been discussed
> on linux-kernel many times.  See
> 
>    http://kt.linuxcare.com/kernel-traffic/kt20000417_63.epl#5
> 
> for some discussion.  Basically, pulling _all_ the special info
> from a CD is a user-land problem.  Defining a file format for the
> reading/burning apps to use is a user-land problem.
>

I'll check out the discussion above. But as you sum up it is really
something to be done as an application rather than allowing the audio to be
read by the kernel. I don't expect the kernel to be able to read the audio
format, but if it's possible I would like to get around it.
 
> And if the currently-available tools don't suit, then either
> 
>    1. Improve the tools
>    2. Write new tools
>    3. Pay someone to do 1 or 2
>    4. Make a case to the maintainers of the tools
>       to add these features.

Firstly, I don't know if the currently-available tools don't suit. The
previously mentioned don't as far as I know, but then there could be
features (options) that I don't know about which would help me out. Maybe
someone else has copied a CD-Extra before and can help me out in trying to
do it myself? But with xcdroast, cdrdao and gnometoaster I've had no
success. 

If it turns out they don't suit then I will attempt to do either 1 or 4.
 From what I've seen xcdroast may be about to wander down this path. If this
is the case then great. As for Writing new tools, 1. I think there are
already more than enough of them out there! and 2. I haven't even the
foggiest idea where to start.

 
> Sorry!

No need to be. All I wanted was to get a few ideas to start looking into.
Can you point me in the right direction for the raw device drivers? Then
I'll see where I can go from there. 

And if anyone has sucessfully copied 1:1 a CD-Extra drop me a line on how
you did it!

Thanks
RikD
 
> Later,
> Kenn
> 
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