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

[Francis Moreau]

On 04/14/2014 06:38 PM, Kay Sievers wrote:
> 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.
> 

yes but I would be deliberately asking to the firmware to write to ESP
in that case.

> 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.

Indeed, that gives one (and only one) reason to use fake raid over soft
one unfortunately.

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

Sad because I'm currently finding the gain to be able to write to ESP
through the EFI shell very tiny compare to be able to have ESP mirrored.

Thanks