Re: [gentoo-user] Re: Reading a DVD as an ISO image

[José Romildo Malaquias]

On Wed, Nov 18, 2009 at 09:36:03AM -0600, Paul Hartman wrote:
> 2009/11/18 José Romildo Malaquias <j.romildo@×××××.com>:
> > On Tue, Nov 17, 2009 at 04:54:20PM +0000, Grant Edwards wrote:
> >> On 2009-11-17, Marcus Wanner <marcusw@×××.net> wrote:
> >>
> >> > My guess is that he has a slow internet connection, he
> >> > downloaded a large iso, burned it, deleted it, and now wants
> >> > to get the iso back without downloading it again, but he has
> >> > access to the checksum/filesize of the original iso from the
> >> > place he downloaded it, and when he makes an iso, the
> >> > checksum/filesize does not match.
> >>
> >> In my experience that happens because one or the other of the
> >> images has "extra" garbage blocks past the end of the actual
> >> ISO filesystem image.  If you look at the ISO filesystem header
> >> and find the actual size of the image, it's probably smaller
> >> than the "image file".  If you only compare the bytes within
> >> the ISO image itself, I bet the two will match.
> >
> > In fact the size of the iso images obtained with dd and with cdread are
> > a little bit larger than the original one. The iso image obtained by
> > mkisofs on the mounted disc (with the udf filesystem type) are of the
> > right size, but still not identical to the original.
>
> This webpage has some info about comaring ISO images to burnt discs
> and a possible solution:
> http://twiki.org/cgi-bin/view/Wikilearn/CdromMd5sumsAfterBurning

Thanks for the link.

As I know the size and the sha1sum of the original ISO image, I
succeeded in creating an identical ISO image from the dvd disc with the
command:

  dd if=/dev/dvd | head -c 4610877440 > /var/tmp/image2.iso

Is it possible to do something similar using readcd instead of dd?

Romildo