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Warning

It has been some time since I’ve set-up a system this way. (as of writing this)

The information be missing some details.

GRUB

Redundant boot disks

EFI boot does not yet support software-raid (MD) => see: Debian documentation - UEFI Grub

After installing the system with a single boot-partition, we will have to reinstall it on the second one!

Disk

You will have to use a second disk to get redundancy.

Create a boot partition at its beginning and mark it as bootable! 512MB should be enough.

Reinstall

First we will have to boot from a live-system! Example Debian Live-system

After that we can install grub on the second disk:

# sda is the new disk
mount /dev/sda3 /mnt
mount /dev/sda2 /mnt/boot
mount /dev/sda1 /mnt/boot/efi
mount --rbind /dev  /mnt/dev
mount --rbind /proc /mnt/proc
mount --rbind /sys  /mnt/sys
chroot /mnt
grub-install /dev/sda --efi-directory=/boot/efi --target=x86_64-efi

Make sure to enable both of the disks in the UEFI/BIOS boot sequence.

Sync

After installing redundant boot-partitions - we still have a problem when doing a system update.

It will only update the kernel version on the currently active partition!

To fix this we can:

Mount both boot partitions in the host system

# find disk ID's
ls -l /dev/disk/by-id/

cat /etc/fstab
> ...
> /dev/disk/by-id/wwn-0x5001b444a60ff504-part1                       /boot/efi  vfat defaults,noatime,nofail 0 2
> /dev/disk/by-id/wwn-0x5001b444a60ff504-part2                       /boot      ext4 defaults,nofail 0 1
> /dev/disk/by-id/ata-SanDisk_X400_M.2_2280_256GB_170839425792-part1 /boot2/efi vfat defaults,noatime,nofail 0 2
> /dev/disk/by-id/ata-SanDisk_X400_M.2_2280_256GB_170839425792-part2 /boot2     ext4 defaults,nofail 0 1

Add a sync script: (/usr/local/sbin/grub_sync.sh)

#!/bin/bash
set -euo pipefail

PATH_BAK='/var/backups/boot'
RETENTION_DAYS=30

if mount | grep "on /boot type" -q && mount | grep "on /boot2 type" -q
then
  mkdir -p "$PATH_BAK"

  echo '### REMOVING OLD BACKUPS of /boot2'
  find "${PATH_BAK}/" -mtime +${RETENTION_DAYS} -name "*.tar.gz" -type f  # to show the files to be deleted
  find "${PATH_BAK}/" -mtime +${RETENTION_DAYS} -name "*.tar.gz" -type f -delete

  echo '### BACKING-UP current /boot2'
  tar -czf "${PATH_BAK}/$(date '+%Y-%m-%d_%H-%M-%S').tar.gz" /boot2/ 2>/dev/null

  echo '### SYNCING /boot to /boot2'
  rsync -av --delete /boot/ /boot2 --exclude "lost+found"
else
  echo 'Missing at least one boot-partition in mounts!'
  exit 1
fi

Add sync job

crontab -e

# sync boot-partitions daily
0 0 * * * /bin/bash /usr/local/sbin/grub_sync.sh