Re: Calling Grub in MBR on a USB disk from Grub on a primary disk problem

[Marcin Zajączkowski]

On Sun, 26 Jul 2009 23:51:11 +0200
Marcin Zajączkowski <address@hidden> wrote:

> Thanks Muchael for your answer!

Michael of course :).


> I didn't have access to that machine during a week and I couldn't
> answer earlier.
> 
> 
> On 2009-08-20 15:14:37 -0700 Michael Evans wrote:
> 
> > What I've found is that modern PC BIOSes are increasingly trying to
> > be too smart and thus acting even more stupid than they should be.
> > It seems that they assume an old 1980s based operating system will
> > be used and remap the devices such that whichever one is actually
> > booting is the 0th and primary bios device.  Your USB device -may-
> > look like a floppy to the BIOS.
> > 
> > My suggestion is to install grub as a whole-disk setup on whatever
> > device you want to boot from, and include a file on that device that
> > you can search for.  Boot off that device, find the file, and modify
> > your device map accordingly.
> 
> I checked it, but it seems that my USB disk is always mapped as hd1
> when booted from primary HDD and as hd0 and booted from USB drive,
> but with your suggestion I was able to locate boot partition and with
> following modifications I'm able to boot!
> 
> title Fedora direct
>       root (hd1,4)
>         kernel /vmlinuz-(...)
>       initrd /initrd-(...)
> 
> > Unfortunately you should not assume any other devices will remain
> > constant, or even predictable.
> 
> Mentioned solution works (and I'm very happy with that!), but it
> requires to modify grub.conf with every new installed kernel version.
> 
> Maybe you have some further ideas how could I debug my system from
> GRUB point of view to make GRUB from the secondary disk MBR bootable?
> 
> 
> Regards
> Marcin