[lug] Hardware/Software Puzzle

Paul E Condon pecondon at mesanetworks.net
Sun Nov 2 20:06:20 MST 2008

On Sat, Nov 01, 2008 at 10:53:25PM -0600, David L. Anselmi wrote:
> Paul E Condon wrote:
> >md5sum /dev/hdd 
> >and 
> >md5sum /dev/hdc
> >
> >This seems to work for CDs that have been manufactured by publishers.
> >For software CDs from, e.g. Intuit, I always get the same md5sum on
> >both reader and reader/writer. But for burnable CDs, I always get an
> >I/O error on the reader/writer and I get a different md5sum on every
> >re-read on the reader.
> Yeah, it's a Linux thing.  Read this:
> http://www.troubleshooters.com/linux/coasterless.htm
> If you use dd to read only the sectors actually part of the CD you 
> should get reliable checksums.


Thanks very much. I think I have the situation under control now.
But there is a little more to the story than your link provided:
The writer writes, and when I read the CD on the reader without 
a count limit I get a file that slightly larger than the original,
17 blocks of 2048 bytes to be exact. This is to be expected and
is OK. 

But when I read the same disk on the writer (it is supposed to read
also and is relatively new), I get a file that is too short by
13 blocks. The overall difference in file length between reading
on the two different drives is 30 blocks. Of course, a count limit
won't fix the reading on the writer. This might be where the padsize
parameter becomes useful, but off hand I don't see how, exactly.

I now have new CDs for netinst of both etch 4.0r5 and LennyBeta2.
The etch CD will boot on all three machines, but the LennyBeta2
will only boot on two. On the third, it spins the CD a bit and
then proceeds to boot from the hard disk. The boot order has been
set properly. I know because the etch netinst CD boots nicely.

So, what can keep one computer from accepting Lenny, while aceepting
etch? Any ideas?

I'm hoping that if I wait until Lenny is a little closer to release,
someone else will have confronted and fixed this feature of Lenny.

For what its worth, the failing machine is a computer sold under the
trade name 'Great Quality' by Fry's in Sacramento. 

Paul E Condon           
pecondon at mesanetworks.net

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