AGM attendees from Cork; Re: [ILUG] Backing up a CD

[Martin Feeney]

On 13 Jun 00, at 8:21, Rik Dunphy wrote:

> Someone else mentioned using dd, but this doesn't work for audio cds. What
> I really need is something that literaly takes the raw binary data from the
> cd and stores it in a file. I don't want the tool to try and understand
> what is on the cd, but to just copy it bit for bit! There are several
> windows tools which can accomplish this, NTI CD Maker Pro for one, but so
> far I've yet to come across anything similar for linux.

Well, first of all nothing can just take the "raw binary data" off a CD.  
CDs are made up of tracks each of which have specific track types.  
Anything that reads from a CD has to at least understand track types and 
how to read them.  It's a very different process reading audio from a CD 
than reading data.  Data is (generally) held in Yellow-book format which 
has a 2k block size and has the remainder of the sector user for 
synchronization.  Audio is in Red-Book format - 2352 bytes of audio data 
per sector with no synchronization (which is why it's notoriously quirky 
reading real-time digital audio from CDs).

If NTI CD Maker Pro writes the entire CD to one binary file it's actually 
doing the job of reading all the data sectors, grabbing the audio and 
putting it all into one large binary file.

If you want something similar that runs under X, check out X-CDRoast, 
Gnome Toaster, BurnIt or CD-Tux for a curses gui. (All can be found in 
part 1 of the CD-Writing HOWTO - http://www.linuxdoc.org/HOWTO/CD-Writing-
HOWTO.html).  They'll write a bunch of files rather than one binary, 
though.

> dd, will check the file format on the CD, and then make a binary file of
> this file format. For a CD this is an iso file, for ext2 it would create a
> binary ext2 file. For some reason it needs to understand the format which
> it is copying...

dd copies the binary image of the data session to a file.  If the data on 
the disc is in ISO format (CD filesystem) then the binary file will be in 
iso format.  If you're reading a cd with an ext2 filesystem on it it'll 
write an ext2 file.  It doesn't need to understand the format at all.  In 
fact it could read an NTFS or FAT32 or even an Amiga filesystem (damn I 
forget what they were called - Kate?).