Promoting/Demoting Nodes, Installing Plugins, Leaving the Swarm, and Further Resources

workloads should be run, such as machines that meet [PCI-SS compliance](https://www.pcisecuritystandards.org/). A compromised worker could not compromise these special workloads because it cannot change node labels. Engine labels, however, are still useful because some features that do not affect secure orchestration of containers might be better off set in a decentralized manner. For instance, an engine could have a label to indicate that it has a certain type of disk device, which may not be relevant to security directly. These labels are more easily "trusted" by the swarm orchestrator. Refer to the `docker service create` [CLI reference](/reference/cli/docker/service/create.md) for more information about service constraints. ### Promote or demote a node You can promote a worker node to the manager role. This is useful when a manager node becomes unavailable or if you want to take a manager offline for maintenance. Similarly, you can demote a manager node to the worker role. > [!NOTE] > > Regardless of your reason to promote or demote > a node, you must always maintain a quorum of manager nodes in the > swarm. For more information refer to the [Swarm administration guide](admin_guide.md). To promote a node or set of nodes, run `docker node promote` from a manager node: ```console $ docker node promote node-3 node-2 Node node-3 promoted to a manager in the swarm. Node node-2 promoted to a manager in the swarm. ``` To demote a node or set of nodes, run `docker node demote` from a manager node: ```console $ docker node demote node-3 node-2 Manager node-3 demoted in the swarm. Manager node-2 demoted in the swarm. ``` `docker node promote` and `docker node demote` are convenience commands for `docker node update --role manager` and `docker node update --role worker` respectively. ## Install plugins on swarm nodes If your swarm service relies on one or more [plugins](/engine/extend/plugin_api/), these plugins need to be available on every node where the service could potentially be deployed. You can manually install the plugin on each node or script the installation. You can also deploy the plugin in a similar way as a global service using the Docker API, by specifying a `PluginSpec` instead of a `ContainerSpec`. > [!NOTE] > > There is currently no way to deploy a plugin to a swarm using the > Docker CLI or Docker Compose. In addition, it is not possible to install > plugins from a private repository. The [`PluginSpec`](/engine/extend/plugin_api/#json-specification) is defined by the plugin developer. To add the plugin to all Docker nodes, use the [`service/create`](/reference/api/engine/v1.31/#operation/ServiceCreate) API, passing the `PluginSpec` JSON defined in the `TaskTemplate`. ## Leave the swarm Run the `docker swarm leave` command on a node to remove it from the swarm. For example to leave the swarm on a worker node: ```console $ docker swarm leave Node left the swarm. ``` When a node leaves the swarm, Docker Engine stops running in Swarm mode. The orchestrator no longer schedules tasks to the node. If the node is a manager node, you receive a warning about maintaining the quorum. To override the warning, pass the `--force` flag. If the last manager node leaves the swarm, the swarm becomes unavailable requiring you to take disaster recovery measures. For information about maintaining a quorum and disaster recovery, refer to the [Swarm administration guide](admin_guide.md). After a node leaves the swarm, you can run `docker node rm` on a manager node to remove the node from the node list. For instance: ```console $ docker node rm node-2 ``` ## Learn more * [Swarm administration guide](admin_guide.md) * [Docker Engine command line reference](/reference/cli/docker/) * [Swarm mode tutorial](swarm-tutorial/_index.md)

This section covers promoting and demoting nodes to change their roles (worker to manager and vice versa), the importance of maintaining a manager quorum. Also describes how to install plugins on swarm nodes using the Docker API, as well as how to remove a node from the swarm using `docker swarm leave` and `docker node rm`. Finally, it provides links to additional resources, including the Swarm administration guide, Docker Engine CLI reference, and a Swarm mode tutorial.