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Support for mirroring of EFI System Partition



Hello Debian EFI support developers,
I would like to install Debian testing on a box with two identical
drives in software RAID1 (mirroring) and I was planning the partition
sizing.
While doing so, I realized that this new box has UEFI (instead of BIOS)
on the motherboard, and hence needs an ESP (EFI System Partition) in
order to host the GRUB bootloader (correct?).

I searched the web about how to set up ESP partitions on two separate
drives in order to be able to boot from any of them, in case one breaks,
and I found scarce and inconsistent information...   :-(

With the old BIOS-based machines, one would simply install GRUB on the
MBR of one drive and then

  # dpkg-reconfigure grub-pc

and select both /dev/sda and /dev/sdb as install devices.

With the new UEFI-based machines, it seems to me that this possibility
is not (well) supported. I read on the Debian Wiki [1] that there's
"no support for putting the ESP on two separate disks in RAID" !

On the other hand, another Debian Wiki page [2] states that you can
dpkg-reconfigure grub-efi-amd64 on EFI systems and select GRUB install
devices. However, I don't see any debconf templates for grub-efi-amd64
in the grub2 source package debian/ directory [3]: does this mean that
grub-efi-amd64 does not support asking the user to select install
devices?

I found a number of places [4] on the web where it is suggested to
manually clone the ESP from one drive to the other with:

  # dd if=/dev/sda1 of=/dev/sdb1

But this should be repeated whenever anything changes on the ESP and I
will sure forget doing so one day or another. There should be a trigger
from the relevant packages (grub-efi-amd64, I suppose, and maybe other
ones) that keeps the "slave" ESPs up-to-date w.r.t. to the "master"
one: is there such a trigger?

So, my question is: what's the recommended way to set up a RAID1 on a
UEFI system and make sure the system will still boot, when any of the
drives breaks?
Is there anything that should be improved in any Debian package?
I can file bug reports, but I am not sure which package I should report
bugs against...

Could anyone please shed some light on this issue?
Thanks for your time and for any help you may provide.


[1] https://wiki.debian.org/UEFI#RAID_for_the_EFI_System_Partition
[2] https://wiki.debian.org/DebianInstaller/SoftwareRaidRoot
[3] https://anonscm.debian.org/cgit/pkg-grub/grub.git/tree/debian
[4] for instance
https://unix.stackexchange.com/questions/69214/partitioning-efi-machine-with-two-ssd-disks-in-mirror


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..................................................... Francesco Poli .
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