Re: [Qemu-devel] Re: Boot Failure (CDROM boot failure code : 0004)

[Paul Brook]

On Monday 16 June 2008, Jens Axboe wrote:
> On Mon, Jun 16 2008, Volkan YAZICI wrote:
> > On Mon, 16 Jun 2008, Laurent Vivier <address@hidden> writes:
> > > could you burn a CD with your .iso and try to boot a real PC ?
> >
> > I created the ISO image from the same CD that's inserted into the
> > /dev/scd0 using below command:
> >
> >   root:~# dd bs=$[1024 * 32] \
> >
> >   > if=/dev/scd0 \
> >   > of=/root/windows-server-2003-standard-x86-64-sp2.iso
> >
> > And I'm sure CD is bootable. (Not pirated, original.) OTOH, if we'd
> > assume the ISO image is corrupted for some unknown reason, why "-cdrom
> > /dev/scd0" didn't work?
>
> You can't just do a dd and expect the output to be bootable, that wont
> include the floppy boot image.

Are you sure? 
Copying all the files and creating a new iso image won't work, but I'm fairly 
sure dd should. My understanding is that the image (which is effectively what 
dd gives you) contains all the data for the el torito bits, but they're not 
neccly accessible via the mounted filesystem.

AFAIK the only times dd isn't give you a sufficient is when you have a 
multimode CD (i.e. audio tracks), when your drive is lying to you because of 
all the encryption stuff, or "copy protection" systems which use deliberately 
broken disks.

Paul