Re: Using dd to copy a cd. Accuracy of the obtained image.
On Wed, 14 Jul 2004 02:55, Antonio Rodriguez wrote:
> I have encountered different problems when trying to copy CDs in
> /dev/hd? to an image in the hard disk. Some times a whole 650 mb
> becomes just 500 kb. I've been doing some reading and googling, and
> among other things found the thread that starts with the message
> http://lists.debian.org/debian-user/2003/03/msg00756.html
> There are several interesting remarks about the use of read-cd, dd,
> etc. There seems to be a general consensus gathered in
> http://www.debian.org/doc/manuals/reference/ch-tune.en.html#s9.3.7
> by Osamu.
> Does anyone have anything to add to this (pointers, howtos, etc)? It
> looks to me as if it could be written and said more about this topic,
> and I am sure that Osamu will be happy with more material to include
> in the reference, and that all will benefit from the discussion.
Whether you use dd or readcd you still need to get the required number of
sectors using mount and df. That takes care of the circumstance where the cd
you are reading has any padding sectors of nulls appended. (I assume you are
trying to get the exact iso image that was used to create the cd).
If the cd reader device turns up in the output of cdrecord -scanbus, then dd
in my experience will be extremely unreliable. OTOH it does seem to work on 1
dvd reader that I have used. That device had no lun etc reported by cdrecord
-scanbus and so could not be used with readcd.
readcd my be invoked in a non-interactive form also so you can use it scripts:
readcd dev=your_device f=the_iso_filename sectors=0-no_of_sectors
HTH
Bob Parker
>
> AR
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