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

[Grant Edwards <grant.b.edwards@gmail.com>]

On 2009-11-18, Jos? Romildo Malaquias <j.romildo@gmail.com> wrote:
> On Tue, Nov 17, 2009 at 04:54:20PM +0000, Grant Edwards wrote:
>> On 2009-11-17, Marcus Wanner <marcusw@cox.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.

Have you tried truncating them to the same length as the
original one and then checking the hash?

> 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.

-- 
Grant Edwards                   grante             Yow! Go on, EMOTE!
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