Playlist "All Systems Go! 2026"
Containers without a new runtime: sdme on systemd-nspawn
sdme is a single static binary that boots systemd-nspawn containers using copy-on-write roots (overlayfs layers or btrfs snapshots), with OCI registry pulling and Kubernetes Pod YAML support. No daemon, no runtime dependency beyond the systemd you already run.
Why I built it. Every container runtime reinvents what systemd already does well: process supervision, logging, cgroups, service ordering, socket activation. sdme makes the opposite bet. systemd-nspawn already boots a full system in isolation; the kernel already gives it a cheap copy-on-write root, whether through overlayfs or a btrfs snapshot. Put a thin, daemonless CLI over the two and you get container workflows (clone, import, pull, run) without a new runtime to install or a daemon to keep alive. It began as a one-command clone of the running host, but the bet is bigger than that: lean on the init system instead of rebuilding it.
What you get. Proper machine-like containers: each one runs a full systemd init with journald, D-Bus, and systemctl, not a single foreground process. Each container is highly configurable through native systemd surfaces, with per-container resource limits, networking, and drop-in config. Clone your running host into a throwaway container in one command; run a Docker Hub image (nginx, redis, postgres) as a managed systemd service instead of a foreground process; deploy a multi-container pod from Kubernetes Pod YAML with health probes, secrets, and configmaps. A rootfs can also come from any distro, an OCI registry, a tarball, or a QCOW2 image, and you can build your own from a Dockerfile-like config.
How it works. One copy-on-write root and one systemd-nspawn invocation give you a fully booted system. Storage is pluggable per container. The overlayfs backend mounts the host / (or any imported rootfs) as an immutable lower layer with a fresh upper, so clones are instant. The btrfs backend snapshots the base rootfs as a subvolume instead, which makes the container root a real filesystem: nested containers work, user namespaces use native idmapped mounts, and per-container disk quotas come from qgroups. It runs directly on a btrfs data directory, or inside a loopback pool image on any other filesystem. The binary does two jobs: it manages those copy-on-write roots, and it drives systemd over D-Bus to start, stop, and supervise containers. Everything else (init, journald, cgroups, service ordering) is systemd doing what it already does, with no daemon in the middle.
Licensed to the public under https://creativecommons.org/licenses/by/4.0/de/