RAID

howto

dans le BIOS

partitions

MDADM

mdadm --assemble --scan

GRUB

esp & boot flags on boot partition

sudo mount /dev/sdaN /mnt
sudo mount --rbind /dev  /mnt/dev
sudo mount --rbind /proc /mnt/proc
sudo mount --rbind /sys  /mnt/sys
sudo chroot /mnt bash
sudo mount /dev/sdaN /
grub-install /dev/sda
sudo chroot /mnt
sudo grub-install /dev/sdx
sudo mount ‐‐rbind /dev /media/xx..xx/dev
sudo mount ‐‐rbind /proc /media/xx..xx/proc
sudo mount ‐‐rbind /sys /media/xx..xx/sys
sudo mount /dev/sdXX /media/xx..xx/boot/efi 
sudo chroot /media/xx..xx
dpkg-reconfigure grub-efi-amd64
grub-install --boot-directory=/mnt/sdcard /dev/sdb
'--boot-directory=DIR'
     Install GRUB images under the directory 'DIR/grub/' This option is
     useful when you want to install GRUB into a separate partition or a
     removable disk.  If this option is not specified then it defaults
     to '/boot', so

          grub-install /dev/sda

     is equivalent to

          grub-install --boot-directory=/boot/ /dev/sda

     Here is an example in which you have a separate "boot" partition
     which is mounted on '/mnt/boot':

          grub-install --boot-directory=/mnt/boot /dev/sdb

https://medium.com/@shivamsaxena2206/install-grub-bootloader-on-a-pen-drive-or-an-external-harddisk-a19584aa1ddf