k3s

K3s is a Kubernetes distribution aimed at machines where a full cluster is overkill: edge devices, ARM boards, CI runners. The README explains how it stays conformant while cutting memory and binary size.

Lightweight Kubernetes. Production ready, easy to install, roughly half the memory, all packed into a binary under 100 MB. The README lists the intended corners: edge, IoT, CI, development, ARM, embedded setups, and any place where running a full Kubernetes stack does not make sense. It even jokes that the name comes from cutting the ten letter word Kubernetes in half, leaving the five letter K3s.

Two main levers. Many components run inside a single process, which removes overhead that would otherwise be duplicated per component. The binary also drops third party storage drivers and cloud providers, both of which have out of tree alternatives like CSI and CCM. The project is careful to call itself a distribution rather than a fork, keeping its own patches well under 1000 lines and pushing fixes back upstream when possible, such as with SELinux support in containerd.

It ships as a single binary with sqlite3 as the default storage backend, while etcd3, MariaDB, MySQL, and Postgres remain supported options. A simple launcher wraps Kubernetes and its components. Worker nodes do not expose the kubelet API port, because that traffic reaches the control plane over a websocket tunnel. It is also secure by default with minimal OS dependencies, just a sane kernel and cgroup mounts.

The distribution comes with containerd and runc, Flannel for CNI, Traefik for ingress, an embedded service load balancer, a network policy controller, a Helm controller for CRD driven manifests, and a datastore shim called Kine that lets etcd be swapped for other databases. A local path provisioner handles volumes from local storage, and host utilities like iptables, ebtables, and socat are included.

K3s tracks upstream Kubernetes releases, aiming for patch releases within a week and new minors within 30 days. Versions carry a +k3s postfix to stay semver compliant when extra releases are needed against the same upstream version. A single install script downloads the binary, sets up a systemd or openrc service, and writes a kubeconfig to /etc/rancher/k3s/k3s.yaml.

The interesting choice is keeping upstream Kubernetes compatibility while being honest about what gets removed and why. The release notes suggest a project that ships often and stays close to upstream.

• Source 1 · Project repository
• Source 2 · README