Re: Soft RAID and EFI systems

[Francis Moreau <francis.moro@gmail.com>]

On 02/04/2014 09:48 AM, David Brown wrote:
> On 04/02/14 09:41, Francis Moreau wrote:
>> On 02/02/2014 11:57 PM, Phil Turmel wrote:
>>> On 02/02/2014 05:30 PM, Chris Murphy wrote:
>>>>
>>>> On Feb 2, 2014, at 2:34 PM, Francis Moreau <francis.moro@gmail.com>
>>>> wrote:
>>>>>
>>>>> That's funny because one of the reasons I want to use UEFI firmware
>>>>> is to get rid of grub (I don't like it and the way it has become
>>>>> such a bloated beast): since /boot is vfat and has its own
>>>>> partition, I prefer use a much simpler bootloader such as
>>>>> gummyboot.
>>>
>>> Ditching the bootloader is possible:
>>>
>>> http://kroah.com/log/blog/2013/09/02/booting-a-self-signed-linux-kernel/
>>>
>>
>> Well yeah it's possible but not currently usable IMHO. It means that you
>> need to build your own kernel, include in this kernel the initramfs
>> image and you need to redo the whole process if you want to change a
>> single option in the kernel command line.
>>
>>> It seems to me that you should be able to create a raid1 v1.0 MD array
>>> of your EFI support partitions, and put the combined and signed
>>> kernel/initramfs onto it (mirrored to all member drives).
>>
>> Are both v0.9 and v1.0 MD  put their metadata at the end of a partition
>> ? I thought only v0.9 would do that.
> 
> Yes, it is only 0.9 format that is at the end of the partition.  This
> means that a plain raid1 mirror (with as many disks as you like, as long
> as they are simple mirrors and not raid10) looks just like a normal
> partition for other tools.  As long as it is read-only, tools that are
> not raid-aware can use it.  For example, grub and lilo can happily boot
> from a 0.9 metadata raid1 array just like from a normal partition.
> (Actually, modern grub understands a lot of md raid formats.)  The same
> thing should apply to EFI, as long as it does not attempt to write to
> the partition.
> 

hmm I need to check if EFI specifies that the ESP is never written by
the firmware. If not it might be risky to rely on it.