Docker Swarm vs K3s

Docker Swarm is an open-source, free orchestration mode built into Docker Engine for managing clusters of Docker daemons in production. It is controlled through the Docker CLI and needs no separate orchestration software. Managers maintain a declarative desired state covering replica counts, networks, storage resources, and exposed ports. Services can be replicated across selected nodes or run globally with one task on every node. Overlay networks connect daemons, while an ingress network provides load balancing. Swarm assigns DNS names and supports virtual-IP load balancing or DNS round-robin discovery. Updates can roll out incrementally and roll back to an earlier service version. Nodes authenticate and encrypt communications with mutual TLS, requiring at least TLS 1.2. Overlay application traffic is not encrypted by default; IPsec encryption can reduce performance. Swarm is self-hosted, supports rolling updates and policy controls, and lacks multi-cluster management and autoscaling.

K3s is a certified, lightweight Kubernetes distribution for IoT and edge computing. It runs self-hosted on Linux and is released for x86_64, ARMv7, and ARM64. The distribution arrives as one binary or a minimal container image; the site describes the binary as under 70 MB, while documentation says under 100 MB. Documented uses include edge systems, homelabs, IoT, continuous integration, development, ARM single-board computers, air-gapped environments, and embedded Kubernetes. SQLite is the default datastore, with etcd, MySQL, and Postgres available. K3s packages containerd or cri-dockerd, Flannel, CoreDNS, Traefik, ServiceLB, Kube-router, local-path-provisioner, and Spegel. High-availability deployments can use embedded storage or external MySQL, PostgreSQL, or etcd. Air-gapped installation supports private registries, manually deployed images, or an embedded registry mirror. Security guidance includes hardening and CIS self-assessment material. Automated Kubernetes-native upgrades use Rancher’s system-upgrade-controller.