What does the DVD media check if installing a new Fedora version? / Proposal

[Joachim Backes]

Hi,

having the following question: What does the DVD/CD media check exactly
if booting a Fedora DVD/CD? Is it the sha256sum? If yes, why this media
check, because it could be done after having burned the DVD?

If not, is it possible to perform this media check immediately after
having burned the DVD (means: can I start the media check from that
freshly burned DVD?)

Proposal: If not, it would be nice if the media checker would be placed
on the DVD for running in normal mode after the DVD has burned - perhaps
allowing to check both an i386 and x86_64 install DVD.

Kind regards

[Tim]

On Fri, 2010-08-13 at 10:32 +0200, Joachim Backes wrote:
> What does the DVD/CD media check exactly if booting a Fedora DVD/CD?
> Is it the sha256sum? If yes, why this media check, because it could be
> done after having burned the DVD?

You can, but you might strike this problem:  The disc checks out fine on
one drive, but reads badly on another.

So a check checks the disc on that drive, and you may wish to check it
reads fine when you use it on another PC.  Or you may be happy to forgo
re-checking it.
> If not, is it possible to perform this media check immediately after
> having burned the DVD (means: can I start the media check from that
> freshly burned DVD?)

Some burning software already does checksum the burnt disc against the
master, immediately after burning the disc.  I think Brasero does that,
I'm sure others do, too.

[Kevin Kofler]

Joachim Backes wrote:
> having the following question: What does the DVD/CD media check exactly
> if booting a Fedora DVD/CD? Is it the sha256sum? If yes, why this media
> check, because it could be done after having burned the DVD?

You can already do this in K3b, there's a box you can check to verify the 
burned stuff. (If I'm not mistaken, it actually does a bytewise compare 
these days, not a checksum.)

You can also run sha256sum /dev/cdrom and compare the result with the 
published checksums.

Kevin Kofler

[Chris Adams]

Once upon a time, Kevin Kofler  said:
> You can also run sha256sum /dev/cdrom and compare the result with the 
> published checksums.

IIRC, you can in some cases get the wrong value with that due to padding
(but it has been a while since I tried that, so that may not be a
problem now).  If you are looking at the master or mirror directory, you
could use dd to only read the right number of bytes from the disk and
pipe the output to sha256sum.

[Joachim Backes]

On 08/13/10 10:32, Joachim Backes wrote:
> Hi,
>
> having the following question: What does the DVD/CD media check exactly
> if booting a Fedora DVD/CD? Is it the sha256sum? If yes, why this media
> check, because it could be done after having burned the DVD?
>
> If not, is it possible to perform this media check immediately after
> having burned the DVD (means: can I start the media check from that
> freshly burned DVD?)
>
> Proposal: If not, it would be nice if the media checker would be placed
> on the DVD for running in normal mode after the DVD has burned - perhaps
> allowing to check both an i386 and x86_64 install DVD.
>
> Kind regards

Hi,

Thanks to all who answered to my question: I think, checkisomd5 will be
the right tool for me (I have only 1 DVD device, so DVD-burner and
DVD-reader are the same).

Kind regards