On Monday 29 December 2008 11:10:10 James E. LaBarre wrote:
> Chris Knadle wrote:
> > What you can do, and should do to prove this for yourself, is to run
> > 'md5sum' and/or 'sha1sum' on the downloaded ISO file, and then on the
> > CD/DVDs you burnt directly.  i.e. first 'md5sum
> > unbutu-8.10-desktop-i386.iso', and then a checkum on the CD device with
> > the CD in the drive, such as 'md5sum /dev/hda'.  The checksums should
> > come out the same, and most likely will, since the Ubuntu media check
> > passed.  You'll see that in terms of the data written, Nero did the same
> > thing that the program you used in Ubuntu did.
>
> Actually, you can't do reliable md5 checksums for comparison by simply
> addressing the drive directly.

I've done it on several occasions and have gotten fairly consistent
results, otherwise I wouldn't have suggested it.  I'm not saying
you're wrong, though -- you've outlined an interesting issue about
this that I haven't run into yet.  Up to this point I have quite
literally done a checksum directly on the device as well as an ISO
file and had them come out the same.

> The writer may write extra data to the disk when closing the session, etc.

Padding, maybe?  Weird.  Haven't seen that yet.

Thanks for posting the link, so I'll know what to try next if the
md5sum on a file and a CD doesn't match.

   -- Chris

-- 

Chris Knadle
[email protected]
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