Re: Issue with boot != root and chainloading

[Pavel Roskin <proski@gnu.org>]

On Tue, 2008-07-22 at 16:01 +0200, Felix Zielcke wrote:
> From: "Pavel Roskin" <proski@gnu.org>
> 
> 
> > I've seen that fd1 somewhere, but I don't remember where.  I guess  
> > GRUB just defaults to that value if it cannot figure out the real  
> > device number of the root device.
> > 
> 
> Maybe this Debian bug ? :)
> For the reporter fd0 wasn't in device.map
> 
> http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=467501 

That's it.  The "id" field doesn't represent the BIOS ID anymore.  It's
just a sequential number now, perhaps the entry number in device.map,
not counting invalid devices.  But it's written to a field where the
bootloader expects to find a BIOS ID, such as 0x81 for the second hard
drive.

Although grub-setup correctly determines the name of the root device,
such as (hd1,1), there is no code that translates "hd1" into 0x81.  That
code was removed to allow drive names like "hd" without a number, used
on PowerPC machines.

That means that device.map support is already totally broken on i386-pc.
So few people noticed it because cross-drive installs are uncommon, and
single-drive installs rely on the boot drive supplied by BIOS.

-- 
Regards,
Pavel Roskin