Re: k3b failure [was Re: [debian-knoppix] Is knoppix getting behind?]
On Mon, Mar 07, 2005 at 01:06:17AM -0500, D. Hugh Redelmeier wrote:
> | From: mark everton <markeverton1@yahoo.com>
>
> | I can't use k3b to burn cd's Every time it fails.
> | This is the case with knoppix 3.7 and all 2.6 kernels
> | I used after that. This is a know problem for some
> | time now.
>
> k3b on a 2.6 kernel burns .iso files correctly for me. A k3b check of
> the result generally fails. I do a different kind of check and the
> created CDs almost always pass.
>
> I will explain my understanding of what is going on. Beware: I could
> be wrong.
>
>
> Summary: when treating the raw CD drive as a file, the wrong length is
> provided by the ide-cd driver. This length includes runout sectors at
> the end of the content and these sectors will generate I/O errors when
> k3b's md5sum reads them for checking purposes. Even if there were no
> I/O errors, the md5sum would be wrong since it includes extra
> (non-content) sectors. Hence, k3b's tests fail.
I believe this is correct. Unless the image is exactly aligned with a multiple
of the sector size (2048 bytes, I believe), and padding is set to "off", the
burning process will automatically add zeros to fill the last sector, which
results in a different md5sum if you verify /dev/cdrom vs the original image.
Or, as you described below, the system calls which return the CD size, simply
give "slightly false" results.
What you could do is a
dd if=/dev/cdrom bs=1 count=size_of_the_iso_file | md5sum
(for better performance, use bs=64k and divide size_of_the_iso_file by 64k).
This should give you the same result like md5sum file.iso, in any case
(ide-scsi or atapi burning mode).
Regards
-Klaus Knopper
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