Swarm mode

• Since version 1.12, the Docker Engine embeds SwarmKit

• All the SwarmKit features are "asleep" until you enable "Swarm mode"

• Examples of Swarm Mode commands:

  • docker swarm (enable Swarm mode; join a Swarm; adjust cluster parameters)

  • docker node (view nodes; promote/demote managers; manage nodes)

  • docker service (create and manage services)

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• The Docker API exposes the same concepts

• The SwarmKit API is also exposed (on a separate socket)

Swarm mode needs to be explicitly activated

• By default, all this new code is inactive

• Swarm mode can be enabled, "unlocking" SwarmKit functions
  (services, out-of-the-box overlay networks, etc.)

• Try a Swarm-specific command:

  docker node ls
  

You will get an error message:

Error response from daemon: This node is not a swarm manager. [...]