I just found a workaround for the problem. I can still not attach via lxc-attach to the containers. However, through a desperate attempt I found out that lxc-attach can still execute commands inside the container (lxc-attach -n <CONTAINER_NAME> -- whoami). Since they are executed as root, I just installed a SSH server and created a user with enabled password in it.
Still this solves not the issue, but allows to update and work inside the container. Cheers, sqall
