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I'm experimenting with booting root filesystem from LVM volume inside the raid (mdraid superblock 1.x) via UEFI with GRUB2. Also I'm using Xen hypervisor.

From grub command line I can see my lvm volume (ls command) but I got kernel panic due to "unable to mount root fs". I saw a note in this article telling it's probably impossible to boot root fs from raid via UEFI, but I don't understand the reason why not.

Is it possible to boot linux with this configuration without the initramfs (which I don't want to use)?

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2 Answers 2

No promises, but: You can try putting the kernel on the EFI System Partition (ESP), or on any other non-RAIDed partition. My own recommendation would be to use the kernel's own EFI stub loader as the boot loader, in conjunction with rEFInd or gummiboot if you want a boot menu that appears automatically or that's superior to whatever your firmware offers. Granted, you won't get the benefits of RAID for your kernel this way, but sticking a kernel on a USB flash drive or whatever for emergency purposes shouldn't be too hard.

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+1 for interesting tips. But finally I used initrd, at this moment Grub2 multiboot is working good so I can use Xen kernel and all that pciback parameters. I'm not happy with initrd but it works. For emergency puropes I'm using gentoo minimal on USB and chrooting... –  dmnc Nov 20 '12 at 10:33

you can't boot from lvm without initramfs, why don't use it?

rationale behind is: lvm volumes has to be activated, initramfs takes care of it, also i think mdadm 1.X needs to be activated too. (0.9 can be activated by kernel itself)

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Yes, the poit was about Grub2 which can see logical volumes (even under RAID), this is very good, but useless while I still must use initramfs due to kernel. I got it later. Maybe in future, kernel'll be possible to init 1.x superblocks. Less or more, as I commented earlier, today I'm using initramfs. –  dmnc Jan 28 '13 at 11:08

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