docker swarm leave

Warning: this command is part of the Swarm management feature introduced in Docker 1.12, and might be subject to non backward-compatible changes.

Usage:  docker swarm leave [OPTIONS]

Leave the swarm (workers only).

Options:
      --force   Force this node to leave the swarm, ignoring warnings
      --help    Print usage

When you run this command on a worker, that worker leaves the swarm.

You can use the --force option to on a manager to remove it from the swarm. However, this does not reconfigure the swarm to ensure that there are enough managers to maintain a quorum in the swarm. The safe way to remove a manager from a swarm is to demote it to a worker and then direct it to leave the quorum without using --force. Only use --force in situations where the swarm will no longer be used after the manager leaves, such as in a single-node swarm.

Consider the following swarm, as seen from the manager:

$ docker node ls
ID                           HOSTNAME  STATUS  AVAILABILITY  MANAGER STATUS
7ln70fl22uw2dvjn2ft53m3q5    worker2   Ready   Active
dkp8vy1dq1kxleu9g4u78tlag    worker1   Ready   Active
dvfxp4zseq4s0rih1selh0d20 *  manager1  Ready   Active        Leader

To remove worker2, issue the following command from worker2 itself:

$ docker swarm leave
Node left the default swarm.

To remove an inactive node, use the node rm command instead.

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https://docs.docker.com/v1.12/engine/reference/commandline/swarm_leave/