On Thu, May 25, 2000 at 11:53:50AM -0500, Peter Seebach wrote:
> Would someone with some scratch space kindly verify whether or not I'm
> deranged:
> 
> 	$ dd if=/dev/cd0a of=cd
> 
> I believe this should come up with a CD image.

I usually use the raw device but I would expect this to work as well ...

> 
> It comes up with something 4 times the size of a CD image.
> 
> I am assuming this is because CD's really use 2048-blocks, not 512-blocks,
> but "disklabel cd0" reports partition sizes in 512-blocks.
> 
> Thus, given the 1.4.2 CD I picked up at Comdex, disklabel says:
> 
>   bytes/sector: 2048
>   sectors/track: 100
>   tracks/cylinder: 1
>   sectors/cylinder: 100
>   cylinders: 2855
>   total sectors: 285442
> 
>   but then says:
>   a:  1141768        0    ISO9660                        # (Cyl.    0 - 11417*)
> 
> So, what am I getting?  What I seem to get (tested this both on i386 1.4.2 and
> Alpha -current) is 4 copies of each 2048-block.  I am totally unable to
> explain this.  I can see that what's happening must be some confusion where
> each of the 512-blocks in a 2048-block comes back as all 2048 bytes of data,
> but isn't that impossible?

Did you try 'dd if=/dev/cd0a of=cd bs=2k' ? If that works it could give an
interesting point.
I tried a similar command on sd0a and got a panic
'getblk: block size invariant failed'.

--
Manuel Bouyer <bouyer@antioche.eu.org>
--