Subject: Re: Okay, now I'm stumped.
To: Peter Seebach <email@example.com>
From: Manuel Bouyer <firstname.lastname@example.org>
Date: 05/25/2000 21:29:34
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
> $ 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
I tried a similar command on sd0a and got a panic
'getblk: block size invariant failed'.
Manuel Bouyer <email@example.com>