Re: GRUB2, GPT, mdadm & LVM

[Chris Murphy]

On Jul 18, 2013, at 5:56 AM, Sander Smeenk <address@hidden> wrote:
> 
> During boot, GRUB starts and drops to 'grub rescue>' stating "Error:
> disk lvm/fdi-host_root not found".

This means it's not finding normal.mod or grub.cfg. Normally those are in the 
grub folder, which is on /boot. So it's a bit curious that it's looking for its 
files on an lvm root rather than on /boot. At the rescue prompt you can type 
set and see what the prefix is. That should point to the grub folder.


> Typing 'ls' in the rescue shell shows
> the '(md/0)' device, but LVM is never started by GRUB.

Only if /boot/grub files are also on LVM is that needed, in which case lvm.mod 
needs to have been baked into the core.img. But the fact that you're getting 
this message sounds like it's not loading lvm.mod.

I forget, but lsmod might work in the grub rescue shell to list what modules 
are available in core.img.


> I tried (re)creating the core.img like so:
> | # grub-mkimage -o /boot/grub/core_lvm.img -O i386-pc \
> |     part_gpt part_msdos mdraid09 mdraid1x raid6rec \
> |     diskfilter lvm ext2
> 
> And put that in all the disks:
> | # grub-bios-setup -b i386-pc/boot.img -c core_lvm.img /dev/sdX

You might be better off using grub-install --debug and figuring out how it 
identifies the various parts. Unless /boot/grub is on LVM, it doesn't 
necessarily need that. It sounds like possibly the prefix is set wrong.


Chris Murphy