Subject: Re: dd from raw devices
To: None <firstname.lastname@example.org>
From: Peter Seebach <email@example.com>
Date: 05/24/2000 17:50:39
In message <Pine.NEB.firstname.lastname@example.org>, Bi
ll Studenmund writes:
>On Wed, 24 May 2000, Peter Seebach wrote:
>> So, I was looking at a NetBSD 1.4.2 CD, and I noticed that it claims to have
>> ~110,000 sectors in cd0a, which is about right if they're 512-byte sectors,
>> but it also claims to have 2048-byte sectors. The end result is that I can
>> 'dd' at least a full gigabyte off of a ~550-580MB CD-ROM.
>What is doing this claiming?
>> Feature? Bug? I certainly found it surprising. I was using bs=2k, I'm not
>> sure if that's relevant. (Hmm. Nope, same problem using bs=512)
>No, that just means that dd will read and write bs bytes at a time.
I figured, but I know CD's are weird.
So, what I think is happening is, we're reading 110,000 2048-blocks from the
CD, even though what it really has is 110,000 512-blocks. My big question
is, where does the extra data come from? It didn't look to be zero-filled.