Classic Swarm has been archived and is no longer actively developed. You may want to use the Swarm mode built into the Docker Engine instead, or another orchestration system.
Docker Swarm "Classic" is native clustering for Docker. It turns a pool of Docker hosts into a single, virtual host.
Docker Swarm "Classic" standalone: This project. A native clustering system for Docker. It turns a pool of Docker hosts into a single, virtual host using an API proxy system. See Docker Swarm overview. It was Docker's first container orchestration project that began in 2014.
Swarmkit: Cluster management and orchestration features in Docker Engine 1.12 or later. When Swarmkit is enabled we call Docker Engine running in swarm mode. See the feature list: Swarm mode overview. This project focuses on micro-service architecture. It supports service reconciliation, load balancing, service discovery, built-in certificate rotation, etc.
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