On 21/01/2023 at 15:04, Wols Lists wrote:

On 21/01/2023 13:32, Pascal Hambourg wrote:

quoted

Back on topic, if you mean Windows+Linux dual boot, it seems unlikely 
to me that this can be achieved with Linux software RAID, because 
Windows does not support it and Windows software RAID usually works on 
whole drives.
If you mean Linux dual-boot, you do not need multiple boot loaders, 
one single boot loader can boot all Linux systems.

Given that this all started with *MIRRORING* EFI partitions, I think 
you've lost the thread ...

I'm fully in agreement that - if we want to keep our EFI partitions in 
sync - then doing so when the partition is updated is the best TIME (not 
place) to do it. (Which is why mirroring makes sense.)

It's just that - as soon as you bring multiple OSes (of any sort) into 
it - this ceases to be a practical solution.

It depends if you mean "mirroring" with rsync or with RAID.
Also, it depends what the OS sorts are. With only Linux systems all 
using EFI partitions in RAID1, it might work.

THERE'S TOO MANY WAYS TO SKIN THIS CAT and trying to automate it will in 
almost all cases lead to tears :-(

This is why I claim that the only universal solution is that each OS 
supports multiple EFI partitions natively when writing any file in an 
EFI partition. Mirroring is a dead end.