Is multi-GRUB2 setup possible?

[S O]

Hello,

I am trying to set up development/test system that needs to have two instances of Windows and several instances of Linux bootable.

Ideally all Linux instances should be as much compartmentalized as possible and not share /boot partition.

For example, kernel files in multiple distributions/instances can have the same name (such as "vmlinuz-3.5.0") but be actually different, e.g. in bitness (such as 32-bit Ubuntu vs. 64-bit Ubuntu) or in kernel build parameters used by different distributions.

My initial idea was to use Windows loader as first stage bootstrap, with BCD database controllable by EasyBCD and having entries for Linux instances. The plan was for each Linux instance to have separate (BOOT,ROOT) partition set or separate single BOOT+ROOT partition, with GRUB2 for a particular instance loaded by WINLOAD off partition selected via WINLOAD menu.

Partition structure could be like this:
 
    WIN1, WIN2, LINUX1-BOOT, LINUX1-ROOT, LINUX2-BOOT, LINUX2-ROOT, LINUX3-BOOT, LINUX3-ROOT etc.

Or:

    WIN1, WIN2, LINUX1-ALL, LINUX2-ALL, LINUX3-ALL etc.

Where "ALL" means single partition holding both root (/) and /boot.

It looks like it cannot work this way because when GRUB is loaded from LINUX2 or LINUX3, it takes "grub.cfg" and other files (such as vmlinuz and initrd) from LINUX1 partition, and not from the GRUB originating partition.

According to EasyBCD developer, in case of multi-instance GRUB2 installation there is no way (or at least he found no way) to indicate to GRUB2 what partition should be used as "currently selected" GRUB partition.

I wished to double-check if this is indeed the case that GRUB2 always falls back to the same partition for GRUB files (including "grub.cfg" and Linux kernel files), no matter what partition GRUB2 itself comes from, and there is no way to indicate to GRUB2 what partition should currently be used for files.

In other words, if this is indeed true that there can be no usable multi-GRUB installation on the machine, and the only solution is to resort to single BOOT partition shared by all Linux instances (with all the accompanying inter-instance interference mess in this partition).

Thanks for any advise.

- Sergey