[NTLUG:Discuss] grub loader messing with my head

[Bryan J. Smith]

On Thu, 2004-09-16 at 10:22, Patrick R. Michaud wrote:
> You can still boot to windows -- assuming that windows is on the
> first partition of the first hard disk (where it almost always is),
> do the following from the grub> prompt:
>    grub> rootnoverify (hd0,0)
>    grub> makeactive
>    grub> chainloader +1
>    grub> boot
> This should get back to windows.

Does GRUB fit entirely in the 512 byte MBR?  Or does it either use
additional sectors in cylinder 0 or files from the Linux partition?
Your solution should work as long as it's not the latter.

> You can then restore the MBR from windows -- but doing so will also
> largely eliminate your ability to boot to the linux installation on
> the external usb.   

My recommendation would be to re-install the MBR for XP by booting XP CD
#1.

Then I would install GRUB on the MBR of the USB drive, and setup the
BIOS to boot a USB device first.  If no USB storage device is plugged in
and bootable, it should boot the internal HD first -- thus XP.  The two
MBRs are completely separate then.

The only kicker is that you might have to setup GRUB's disk mapping so
the USB storage device is BIOS disk 80h (hd0).  Otherwise you'll get a
kernel panic once it tries to load the root filesystem and assumes BIOS
disk 80h is /dev/hda.

Under RHL/FC, the mapping is set in the file "/boot/grub/device.map".

> You might also try booting to linux and installing LILO instead of
> grub (or reinstalling linux with LILO).  Normally I prefer grub but
> in this instance LILO might be able to handle it better.

LILO would probably make recovery worse IMHO.

I would just keep the XP and Linux MBRs separate.  If Linux is on the
external USB drive, then it's not an issue if its not plugged in.  This
requires a BIOS that can boot a USB storage device


-- 
     Linux Enthusiasts call me anti-Linux.
   Windows Enthusisats call me anti-Microsoft.
 They both must be correct because I have over a
decade of experience with both in mission critical
environments, resulting in a bigotry dedicated to
 mitigating risk and focusing on technologies ...
           not products or vendors
--------------------------------------------------
Bryan J. Smith, E.I.         b.j.smith at ieee.org