Docker Swarm Basics

Docker Swarm is Docker's native container orchestration tool used to manage a cluster of Docker nodes as a single system. It helps you deploy, scale, and manage containerized applications across multiple machines.

What is Container Orchestration?

Container orchestration automates:

• Deployment of containers
• Scaling applications up or down
• Load balancing traffic
• Managing container health and failover

Key Concepts in Docker Swarm

Initialize Docker Swarm

docker swarm init

This command turns your machine into a manager node.

Add Worker Nodes

docker swarm join --token <token> <manager-ip>:2377

Deploy a Service

docker service create 
  --name my-nginx 
  -p 8080:80 
  nginx

Scale a Service

docker service scale my-nginx=5

This runs 5 replicas of the container across nodes.

List Services and Nodes

docker service ls
docker node ls

Inspect and Update Service

docker service inspect my-nginx
docker service update --replicas 3 my-nginx

Remove Service

docker service rm my-nginx

Docker Swarm vs Kubernetes

Summary

• Docker Swarm is used for container orchestration.
• It manages multiple Docker nodes as a single cluster.
• Use docker service commands to deploy and scale apps.
• Best suited for simple and medium-scale deployments.