Couldn’t Resolve Device rpool/ROOT During Update-Initramfs

The following is on Ubuntu 20.04.1 LTS:

During update-initramfs I was getting the following message:

$ sudo update-initramfs -c -k all
update-initramfs: Generating /boot/initrd.img-5.13.0-21-generic
cryptsetup: ERROR: Couldn't resolve device rpool/ROOT
cryptsetup: WARNING: Couldn't determine root device

The solution was to update file /usr/share/initramfs-tools/hooks/cryptroot function get_mnt_devno() and change the line:

    done </proc/mounts

.. to ..

    done </etc/fstab