This must be a very unusual use case, but I actually want to copy a container from a host running LXD 3.0.2 (18.04 stable) to one running 2.0.11 (16.04 stable). I needed push migration support to do an lxd-p2v, but now want to move the container to another host. Despite many options to override configuration, I couldn’t get rid of the unknown key pool when migrating.
lxc copy container host:
Error: Failed container creation: Invalid device configuration key for disk: pool
I was able to solve this by creating a profile and attaching it to my container, then moving the root device to the profile and removing it from the container config. I made a copy of the profile with the same name on the destination host, but without the offending pool key. Posting here in case it helps someone else.