Swarm Operations

Promote and Demote Nodes
Promote a Worker to Manager
Demote a Manager to Worker
Drain a Node for Maintenance
Remove a Node from the Swarm
References

In this lesson, you’ll learn how to:

Promote and demote Swarm nodes
Drain nodes for maintenance
Remove nodes from your cluster

These operations help maintain high availability and streamline cluster management.

Promote and Demote Nodes

Only Swarm manager nodes can orchestrate the cluster. You can elevate a worker node to manager or revert a manager back to a worker. Run these commands on any current manager.

Promote a Worker to Manager

docker node promote worker1

Promoting a node requires you to be connected to an active manager. Check your current context with docker info.

Verify the updated node list:

ID	HOSTNAME	STATUS	AVAILABILITY	MANAGER STATUS	ENGINE VERSION
91uxgq6…	manager1	Ready	Active	Leader	19.03.8
2lux7z6…	worker1	Ready	Active	Reachable	19.03.8
w0qr6k2…	worker2	Ready	Active		19.03.8

Demote a Manager to Worker

docker node demote worker1

Confirm the demotion:

ID	HOSTNAME	STATUS	AVAILABILITY	MANAGER STATUS	ENGINE VERSION
91uxgq6…	manager1	Ready	Active	Leader	19.03.8
2lux7z6…	worker1	Ready	Active		19.03.8
w0qr6k2…	worker2	Ready	Active		19.03.8

Drain a Node for Maintenance

Before patching or upgrading, remove workloads from a node to avoid downtime. The following diagram shows a Swarm cluster with one manager and two workers running a “Web” service.

The image illustrates a Docker Swarm setup with three nodes: one manager node and two worker nodes, each labeled with an IP address and a "Web" service.

Drain worker1 to migrate its tasks:

docker node update --availability drain worker1

Draining a node stops new tasks from being scheduled and reschedules existing ones on other workers. Ensure your cluster has enough capacity before draining.

Check the drain status:

ID	HOSTNAME	STATUS	AVAILABILITY	MANAGER STATUS	ENGINE VERSION
91uxgq6…	manager1	Ready	Active	Leader	19.03.8
2lux7z6…	worker1	Ready	Drain		19.03.8
w0qr6k2…	worker2	Ready	Active		19.03.8

After maintenance, reactivate scheduling:

docker node update --availability active worker1

Now worker1 will accept new tasks:

ID	HOSTNAME	STATUS	AVAILABILITY	MANAGER STATUS	ENGINE VERSION
91uxgq6…	manager1	Ready	Active	Leader	19.03.8
2lux7z6…	worker1	Ready	Active		19.03.8
w0qr6k2…	worker2	Ready	Active		19.03.8

Remove a Node from the Swarm

To permanently remove a worker node:

Drain the node:

docker node update --availability drain worker2

Example confirmation:

Node left the swarm.

At this point, worker2 is safely removed, and your cluster continues with the remaining nodes.

References

Watch Video

Demo Swarm Cluster Setup

Swarm High Availability Quorum

⌘I

Introduction

Docker Engine

Docker Image Management

Docker Engine Security

Docker Engine Networking

Docker Engine Storage

Docker Compose

Docker Swarm

Kubernetes

Docker Engine Enterprise

Docker Trusted Registry

Disaster Recovery

Promote and Demote Nodes

Promote a Worker to Manager

Demote a Manager to Worker

Drain a Node for Maintenance

Remove a Node from the Swarm

References

Watch Video

Introduction

Docker Engine

Docker Image Management

Docker Engine Security

Docker Engine Networking

Docker Engine Storage

Docker Compose

Docker Swarm

Kubernetes

Docker Engine Enterprise

Docker Trusted Registry

Disaster Recovery

​Promote and Demote Nodes

​Promote a Worker to Manager

​Demote a Manager to Worker

​Drain a Node for Maintenance

​Remove a Node from the Swarm

​References

Watch Video

Promote and Demote Nodes

Promote a Worker to Manager

Demote a Manager to Worker

Drain a Node for Maintenance

Remove a Node from the Swarm

References