The latest release of nspawn, version 3.0, introduces a Docker-compatible Engine API for systemd-nspawn containers, allowing tools that manage containers through the Docker API to work with nspawn's machines. This means that tools like GitLab Runner's docker executor can now utilize nspawn's containers, and the docker command can be used to manage them by pointing DOCKER_HOST at nspawn's API socket. The API server is a client of the bus service and operates under the same polkit actions as the command line, with every user able to connect, but requiring specific permissions to perform certain actions, such as inspecting or managing containers.