[Mageia-dev] Grub2 vs. Grub Legacy in M3

[Frank Griffin]

On 01/20/2013 02:58 PM, Maurice Batey wrote:
> On Sun, 20 Jan 2013 20:04:32 +0200, Thomas Backlund wrote:
>
>> http://svnweb.mageia.org/packages/cauldron/grub2/current/SOURCES/README.Mageia?view=markup
>    Many thanks, Thomas!
>
Look, I don't don't want to restate the obvious, but you *do* realize 
that in order for chainloader to work, you actually have to install the 
secondary bootloader on the PBR of its owing partition ?  You can't just 
have installed grub on your MBR at some point in the past, then install 
grub2 (or anything else, for that matter) on the MBR again, and expect 
your original partitions to boot ?

In MGA install terms, and specific to the case of grub2 on the MBR 
trying to boot grub on a PBR, you have to boot the grub partition (or do 
the boot-elsewhere/chroot thing), modify the /boot/grub/install.sh to 
not target the MBR (stage2=(hd0)) but indicate the PBR (stage2=(hd0,x)) 
and rerun install.sh to install grub on the PBR.

In terms of the install paradigm, you have to choose to install the 
bootloader to the PBR (sdaX) rather than the MBR (sda).  Otherwise, when 
the MBR bootloader, whether grub2 or grub, boots and chains to the PBR 
of the desired partition, there won't be anything there in the PBR to boot.

If you need clarification on this, ask, and give specifics.  The 
objective of chainloading is to have each PBR (partition) behave as if 
it is its own MBR.  If you try to point grub2 menu entries to native 
partiton grub files, or vice versa, you are just asking for trouble.  
The clean way to do it is to use chainloading to link the MBR (whatever 
it is) to the PBR (whatever it is), and let the PBR do the bootloading 
for its own partition according to its own needs.

If you do it this way, you can install whatever you want as a bootloader 
on the MBR, and each partition can have whatever BIOS-compliant 
bootloader it wants, including grub, grub2, lilo, OS/2, DOS, or Wndows.