libcontainer is part of runc (opencontainers/runc in GitHub) and is used by the Docker and containerd ecosystem to spawn containers. This work is trying to bridge the gap between the Docker/containerd/Kubernetes ecosystem and cgroup2 through the unified hierarchy, using systemd as an authoritative container manager. I'll also touch on alternative approaches (such as crun and systemd-nspawn) and briefly talk about the OCI standard and the need for it to evolve to properly support cgroup2 semantics.