Re: Initial Program Loader in Hybrid MBR/GPT

[Andrey Borzenkov]

В Fri, 1 Mar 2013 23:37:28 -0600
Knapper <address@hidden> пишет:

> I want to be able to move a drive between a BIOS system and a UEFI system.
>  It seems possible when considering that an MBR's IPL would be loaded by a
> BIOS machine while the GPT's 'boot' flagged partition with an EFI
> application would be loaded on UEFI systems, assuming the UEFI firmware
> isn't buggy.
> 
> I understand how to convert the protective MBR to a hybrid MBR that BIOS
> machines can read.  I am less clear about how to get a working Initial
> Program Loader installed and configured to go on loading the rest of GRUB2.
>  Is this possible?  Does the content of the IPL depend on the partition
> scheme/configuration?  If not, can I create an MBR installation of GRUB2
> and copy the IPL over to the protective MBR?  If I have a /boot partition
> and a /boot/efi partition, the MBR active flag should be set on the /boot
> partition while the GPT boot flag should remain pointed at the /boot/efi
> partition, correct?
> 


There is no need to use hybrid MBR. Even with GPT first sector is not
used, so you can install grub2 there. core.img can either be embedded
in separate bios_boot partition (see grub2 documentation about it;
partition can be created using e.g. parted or gdisk) or used directly
from filesystem as blocklists (not recommended).

BIOS will simply read the first sector and jump to it. It does not
really care (at least, should not) about partitioning scheme.