I am following https://github.com/openzfs/zfs/wiki/Ubuntu-18.04-Root-on-ZFS but doing it for Ubuntu 20.04.
When I get to:
update-initramfs -u -k all
nothing happens: It returns after 0.1 second and normally
update-initramfs takes several seconds on my machine.
update-grub also complains about a missing initrd:
# update-grub Sourcing file `/etc/default/grub' Sourcing file `/etc/default/grub.d/init-select.cfg' Generating grub configuration file ... Found linux image: vmlinuz-5.4.0-29-generic in rpool/ROOT/ubuntu Warning: Couldn't find any valid initrd for dataset rpool/ROOT/ubuntu. Warning: didn't find any valid initrd or kernel. Found Ubuntu 20.04 LTS (20.04) on /dev/sda5 done
And when booting I get a grub prompt (no menu).
It seems there is some crucial step missing. Something that tells
update-initramfs which initrd to build.
I have tested that the machine can boot on UEFI (the normal, unencrypted ext4 Ubuntu can install just fine with UEFI).