I dug a little bit more, and it seems the problem with docker stems from storage drivers … on both ubuntu:18.04 and ubuntu:16.04 …
In syslog, I see the following:
#ubuntu 18.04
failed to load plugin io.containerd.snapshotter.v1.btrfs" error="path /var/lib/docker/containerd/daemon/io.containerd.snapshotter.v1.btrfs must be a btrfs filesystem to be used with the btrfs snapshotter" module=containerd
#ubuntu 16.04
'overlay' not found as a supported filesystem on this host. Please ensure kernel is new enough and has overlay support loaded.
So, bottom line is that it seems docker is trying to use storage drivers that are not working inside the container … so, overlay in ubuntu 16.04, and btrfs in ubuntu 18.04 …
A few more searching around … and I see (although my issue is not about vfs driver, I think it’s related):
This is Docker’s page on how storage drivers are chosen:
Is there anything I can set in lxd profile for the container that could help ?