[systemd-devel] gummiboot can't be installed on ESP which is soft RAID1 metadata=0.9 partition

[Kay Sievers]

On Mon, Apr 14, 2014 at 9:22 AM, Francis Moreau <francis.moro at gmail.com> wrote:
> On 04/14/2014 06:16 PM, Lennart Poettering wrote:
>> On Mon, 14.04.14 18:01, Francis Moreau (francis.moro at gmail.com) wrote:
>>
>>> "gummiboot install" fails when ESP is MD RAID1 device using metadata 0.9
>>> or 1.0.
>>>
>>> I don't think using such RAID for ESP would lead to issue.
>>>
>>> Is there any reason gummiboot doesn't want to be installed on such
>>> partition ?
>>
>> The installer will make sure that the ESP is on GPT and carries the right
>> type UUID. We do that for safety reasons, since that's the requirement
>> made by UEFI, and how the bootloader is found.
>>
>> You cannot place the ESP on sw RAID, since the firmware might want to
>> write to the ESP (most won't do that, but could, and the tianocore
>> implemenation you use in qemu certainly does).
>
> Does UEFI allow firmware to write to ESP ?
>
> If so that would indeed prevent ESP to be on soft RAID.

Sure, it does. You can just start an EFI Shell and edit any file in the ESP.

The only safe (at least in theory) thing is to have a "bios raid"
driver included in the EFI firmware itself, which sets up the ESP to
be the mirrored disks. With that, writes from the firmware will end up
on both disks without any operating system involved.

Setting up the ESP as a raid without explicit firmware support does
not sound like a good idea.

Kay