md5sum, ISO files and Redhat 8

[Kevin O'Gorman]

Every time I've tried comparing in that way, I've had the same result
you did.  The only comparison I use any more comes from mounting
both the CD and the ISO, and doing a recursive diff on them as
filesystems.

++ kevin


On Tue, 15 Oct 2002, Tim Wunder wrote:

> OK, I'm puzzled by this. Can anyone explain?
>
> I installed RH8 from ISOs I downloaded. I verified each ISO file and they were all good. I then burned CD's 1, 2 and 3 to CDR and attempted to verify them in the following ways:
> 1. Performed 'diff /dev/cdrom /path/to/downloaded.iso'
> 2. Performed 'md5sum /dev/cdrom'
> 3. Performed 'dd if=/dev/cdrom of=/some/file.iso' and ran md5sum on /some/file.iso
>
> In each case, for all three downloads, the CDRs were deemed to be different from the ISO files. As a result, I re-burned CD1 (at a more conservative 4x instead of 8x) and performed all the same tests. It too, found the burned CDR to be different from the ISO file.
>
> I then tested the two files created from both copies of CD1, using dd, and both had the same md5sum, which was different from the source ISO file. I then made the bold assumption that two bad burns couldn't have the same md5sum and determined that the burns *must've* been ok. Which doesn't make sense either.
>
> So, I decided to try the disks anyway to see what would happen. As it turns out, RedHat provides a disk check at the beginning of the install process. I put each of the 3 disks thru redhat's disk check, and each passed the test. I then continued with the install process and managed to get RH8 installed onto 2 different machines using these disks (an AMD Athlon 950 and a K6 450).
>
> Is there any logical explanation why the md5sum of a properly burned CD of an ISO file would have a *different* md5sum than the ISO file? Until recently, I would've said no, the CDR and the ISO should have the same md5sum. But my experience with these RH8 ISOs seems to contradict that.
>
> Regards,
> Tim
>
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