I believe that these are the same
last I tried it. But I assumed that the burning software I used (Nero
on Win2000,) added some identifying headers, or something on the CD.
Thus producing the different MD5. But that still leaves the question
on if the CD is still good or not.
Jeffrey Clement wrote:
I do not believe that this is correct. When you take the MD5SUM of the
cdrom DEVICE (not mounted file system) you are taking the MD5SUM of the
whole cdrom image which should be the same as the ISO that created it.
I'm not 100% on this. It may be that the image gets padded or something
like that. I think what Curtis is talking about is the difference between
the ISO and the actual mounted CD file system and yes those definately are
different. So again I think you can simply do:
cdrecord dev=0,0,0 test.iso
md5sum test.iso
md5sum /dev/scd0 (or whatever)
I think the output from the two MD5 sums should be the same. Does anyone
know for sure on this. I'm pretty sure I've done this before and I believe
it makes sense that this would work.
Jeff
On Wed, Jan 21, 2004 at 12:25:53PM -0700, Curtis Sloan wrote:
On Wed, 2004-01-21 at 11:43, Jason Louie wrote:
But is this producing the same MD5 checksum directly from the CD as
the ISO?
I'm not sure if I understand what you are asking, so let me rephrase the
question and you can correct me if I'm misunderstanding:
"Is the MD5 checksum of the CD (i.e. /dev/cdrom) the same as the MD5
checksum of the .iso file (before it was burned)?"
If this is the question you are asking, then the answer is no. They
will always be different.
The answer lies is in the way the MD5 algorithm works. It produces a
unique 128-bit checksum for any given arrangement of bytes.
In this case, the arrangement of the bytes in an ISO file is distinctly
different than that of the exact same bytes laid out in a filesystem
(i.e. after burning). The MD5 algorithm doesn't care that they are the
same bytes, since (from the algorithm's perspective) the single ISO file
is fundamentally different than the collection of files taken as a
whole. One MD5 will be a "fingerprint" of an ISO file, the other of an
entire filesystem. The difference can seem semantic, but viewed from an
algorithm's point of view, it can make sense.
This may account for apparent discrepancies in MD5s (if I understood
your question correctly).
HTH,
Curtis
I've seem lots of examples on the web on the process of verifying CDs
burnt from ISOs but I can't seem to reproduce the results. I only
have access to a burner on a Win system and I'm wondering if that is
the reason why the MD5s are different.
Pete wrote:
Linux commandline burning works for me...
http://www.yolinux.com/TUTORIALS/LinuxTutorialCDBurn.html
There are a few examples of commands to copy CDs
Peter
Jason Louie wrote:
Has anyone been able to verify the *burned* copy of the ISO? Also
what programs are you guys using for the burning? I'm using Nero
on a Win system. I have lots of distros that I would like to
share but I don't feel good about having them available when I'm
not sure if they're good. I haven't been able to get matching
results with doing an MD5 check on the CD so I was wondering if
anyone has been getting better results.
--
Jason Louie BSc. CPSC
Web Applications Developer
Sorex Software Inc.
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