Deekee wrote: ↑2022-09-21 13:30
Do I just need to set one of the above, so changing the UUID will do?
Yes, you only need to set the one that you will use in fstab, whatever you choose.
Deekee wrote: ↑2022-09-21 13:30
Setting the UUID on the second disk I basically straight forward
You could do it more easily with "fatlabel" (the UUID is called "volume ID") from the package "dosfstools".
Deekee wrote: ↑2022-09-21 13:30
What I don't get is for what are the entries Boot0080 and BootFFFF for?
I guess they were automatically generated from the "removable media path" of some previous EFI partition on either SATA disk.
Deekee wrote: ↑2022-09-21 16:16
not matter how i set the boot order via the efibootmgr it's always mounting sdb1.
Maybe I did not make it clear enough that there is no relationship at all between the booted EFI partition and the mounted EFI partition (and conversely) in my previous post.
Also sda and sdb may not be the same disk at each boot.
Deekee wrote: ↑2022-09-21 16:16
How can I find out from which partition the system is currently booting?
efibootmgr shows the booted entry number in BootCurrent. With the PARTUUID you can find which partition it is.
Deekee wrote: ↑2022-09-21 16:16
If I grep dmesg I just see the UUID of the RAID md0
The kernel command line shows the root filesystem which is not related with the booted partition in any way.
I guess you could set a GRUB variable with different values in /EFI/debian/grub.cfg of each EFI partition and insert this variable in GRUB_CMDLINE_LINUX in /etc/default/grub so that its value appears as a dummy parameter in the kernel command line.