Managing Swarm Nodes

This post will cover topic related to ‘Managing Swarm Nodes’ with multiple docker command examples and different scenerios. So this will help you to understand the command docker and options available in it. Also this post will explain you how to use docker command.

Docker is a powerful tool for containerization that allows managing and deploying applications in isolated environments. When dealing with Docker Swarm, the command docker node becomes essential for managing Swarm nodes.

Here are several examples showcasing how to use docker node effectively:

Example 1: Listing Swarm Nodes
To view all nodes in the Swarm, use:

docker node ls

This command lists all nodes along with their status, availability, and role in the Swarm.

Example 2: Inspecting a Node
To get detailed information about a specific node, run:

docker node inspect <node_id_or_name>

Replace <node_id_or_name> with the actual ID or name of the node. This command provides a JSON representation of the node’s configuration.

Example 3: Adding a Node to the Swarm
To add a new node to the Swarm, execute:

docker swarm join --token <token> <manager_ip:port>

Replace <token> with the join token obtained from the Swarm manager, and <manager_ip:port> with the IP address and port of the Swarm manager. This command joins a node to the existing Swarm.

Example 4: Removing a Node from the Swarm
To remove a node from the Swarm, use:

docker node rm <node_id_or_name>

Replace <node_id_or_name> with the ID or name of the node to be removed. This command effectively removes the node from the Swarm.

Example 5: Updating a Node
To update a node’s resources or labels, use:

docker node update --label-add environment=production <node_id_or_name>

Here, --label-add adds a label to the node, making it identifiable by certain criteria like environment type.

Example 6: Draining a Node
To gracefully stop a node for maintenance, use:

docker node update --availability drain <node_id_or_name>

This command sets the node’s availability to drain, allowing running containers to be rescheduled on other nodes before stopping the node.

Example 7: Promoting a Node to Manager
To promote a worker node to a manager in the Swarm, execute:

docker node promote <node_id_or_name>

This command upgrades the selected node’s role from worker to manager, granting it additional administrative privileges.

Example 8: Demoting a Manager Node
To demote a manager node back to a worker, use:

docker node demote <node_id_or_name>

This command reduces a manager node’s role to that of a worker, redistributing its administrative responsibilities.

Example 9: Updating Node Availability
To change a node’s availability, such as from active to pause, use:

docker node update --availability pause <node_id_or_name>

This command changes the node’s availability status to pause, temporarily halting all container tasks on that node.

Example 10: Verifying Node Status
To check if a node is active and ready within the Swarm, use:

docker node inspect --format '{{.Status.State}}' <node_id_or_name>

This command retrieves the current state of the specified node, ensuring it is operational and ready for container deployment.

Also check similar articles.

Managing Swarm Configurations
Managing Docker Image Trust
Managing Docker System
Managing Docker Plugins
Managing Docker Image Manifests and Lists