systemd-nspawn
systemd-nspawn is a lightweight containerization tool included with systemd that allows users to spawn a minimal namespace container for running commands or full operating systems in an isolated environment. It leverages Linux kernel features like namespaces and cgroups to provide process and resource isolation without the overhead of a full virtualization stack. It is often used for testing, development, and simple container deployments, similar to chroot but with enhanced isolation.
Developers should learn systemd-nspawn when they need a simple, fast, and integrated way to create containers for testing applications in isolated environments, especially on systems already using systemd. It is ideal for use cases like running development builds in a clean environment, testing package installations, or creating lightweight sandboxes without the complexity of Docker or Kubernetes. Its tight integration with systemd makes it convenient for system administrators and developers working on Linux distributions that use systemd by default.