Nspawn 3.0: A Docker-compatible Engine API for systemd-nspawn containers
Summary
Nspawn 3.0 adds a Docker-compatible Engine API to systemd-nspawn containers, enabling management via Docker-style clients while running on the host Linux system. The post documents the API surface (containers, attach, exec, archive, images, volumes, networks), explains the host socket and polkit-based permissions, and outlines breaking changes from 2.x plus upcoming 3.1.0/3.2.0 releases and known gaps. It also highlights real-world usage, including GitLab Runner integration and packaging details.