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

[Frank Griffin]

On 01/20/2013 07:55 AM, Maurice Batey wrote:
> So I suspect that he (like me) does not know how to boot a GRUB Legacy 
> install from a GRUB2 boot menu. (Yes, I know GRUB2 boot menus do show 
> options to boot existing GRUB Legacy installs, but in my experience 
> (with Ubuntu and Mint) they *fail* to boot them.) Despite my requests 
> in various newsgroups, NO ONE has offered a description of how to get 
> a GRUB2 boot menu to successfully boot a GRUB Legacy install. Can you, 
> please, Frank? 

I've never used grub2 myself.  But the article states that if you have 
grub2 on the MBR and define a chainloader menu.lst entry for a partition 
that has grub on the PBR, it works.

That makes sense.  Chainloading simply means that the MBR bootloader 
reads the PBR into memory and passes control to it exactly as the BIOS 
reads the MBR into memory and passes control to it.  Assuming that both 
grub and grub2 support chainloading correctly, neither one of them 
should have any idea whether it's an MBR that was loaded by the BIOS or 
a PBR that was chainloaded by an MBR.

This glosses over other sources of problems like UEFI and GPT, but it 
has always been the case that if you want to support multiple boot 
loaders, you have to use a lowest common denomination architecture that 
they all support.