Re: dd on CDROM?

[Piotrek Kapczuk <piotr@polcomnet.com.pl>]

Hi

2001-10-31, 11:55:41, you wrote:


> Is there some way to read blocks on a cdrom, eg using dd if=/dev/cd0a etc,
> without unmounting the CD?

> I want to read numbered blocks, but as the CD has dd (and root, no HDD) on
> it I can't easily unmount it. Using dd if=/cdrom doesn't work (NetBSD reads
> the first 2k), and if I use dd if=/dev/cd0a when mounted I get "device
> busy".

> (It's to verify the contents of the CD by reading random blocks, hashing
> them, and comparing with the result from a known-good CD. I could put dd on
> a mfs, but I'd prefer another solution as this is hard (only a single
> unionfs works, anyone know why?) and needs more memory)


IIRC OBSD will let you read raw device when it's mounted, when you'll be in
singel user mode.

-- 
Regards
Piotrek Kapczuk