Reinstalling GRUB on a non bootable UEFI Ubuntu 16.04 ZFS installation

You can use the steps below to reinstall grub on a Ubuntu 16.04 ROOT on ZFS  installation.

Step 1: Prepare The Install Environment

1.1 Boot the Ubuntu Live CD, select Try Ubuntu Without Installing, and open a terminal (press Ctrl-Alt-T).

1.2 Optional: Install the OpenSSH server in the Live CD environment: If you have a second system, using SSH to access the target system can be convenient.

$ sudo apt-get --yes install openssh-server

Set a password on the “ubuntu” (Live CD user) account:

$ passwd

Hint: You can find your IP address with ip addr show scope global. Then, from your main machine, connect with ssh ubuntu@IP.

1.3 Become root:

# sudo -i

1.4 Install ZFS in the Live CD environment:

# apt-add-repository universe
# apt update

(ignore errors about moving an old database out of the way)

# apt install --yes debootstrap gdisk zfs-initramfs grub-efi-amd64

Step 2: Discover available ZFS pools

2.1 check if ZFS pools are already imported

# zpool list
# zfs list 

2.2 if so, we need to export the zfs pool so we can mount it in a different directory so we can chroot to it

# zpool export rpool

Step 3: Chroot into ZFS pool

3.1 import pool to non-default location. The -N flag (don’t automatically mount) is necessary because otherwise the rpool root, and the rpool/root/UBUNTU pool, will both try to mount on /mnt

# zpool import -a -N -R /mnt

3.2 mount the root system

# zfs mount rpool/ROOT/ubuntu

3.3 mount the remaining file systems

# zfs mount -a

3.4 Bind the virtual filesystems from the LiveCD environment to the new system and chroot into it:

# mount --rbind /dev  /mnt/dev
# mount --rbind /proc /mnt/proc
# mount --rbind /sys  /mnt/sys
# chroot /mnt /bin/bash --login

Note: This is using –rbind, not —bind.

Step 4: Re-initialise EFI partitions on all root pool components

4.1 Check the wildcard gets the correct root pool partitions:

# for i in /dev/disk/by-id/*ata*part3; do echo $i; done

4.2 Add an entry for /boot/efi for each disk to /etc/fstab for failover purposes in future:

# for i in /dev/disk/by-id/*ata*part3; \
      do mkdosfs -F 32 -n EFI ${i}; \
      echo PARTUUID=$(blkid -s PARTUUID -o value \
      ${i}) /boot/efi vfat defaults 0 1 >> /etc/fstab; done

4.3 mount the first disk

# mount /dev/disk/by-id/scsi-SATA_disk1-part3 /boot/efi

4.4 install grub

# grub-install --target=x86_64-efi --efi-directory=/boot/efi \
      --bootloader-id=ubuntu --recheck —no-floppy

4.5 unmount the first partition

# umount /boot/efi

4.6 mount the second disk

# mount /dev/disk/by-id/scsi-SATA_disk2-part3 /boot/efi

4.7 install grub

# grub-install --target=x86_64-efi --efi-directory=/boot/efi \
      --bootloader-id=ubuntu --recheck —no-floppy

4.8 repeat steps 4.5 to 4.7 for each additional disk 4.9 For added insurance, do an MBR installation to each disk too

# grub-install /dev/disk/by-id/scsi-SATA_disk1
# grub-install /dev/disk/by-id/scsi-SATA_disk2

Step 5: Reboot

5.1 Quit from the chroot

# exit

5.2 Reboot

# reboot