Subject: Re: dd from raw devices
To: None <>
From: Peter Seebach <>
List: current-users
Date: 05/24/2000 17:50:39
In message <>, 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.