Docker Swarm is a native clustering and orchestration tool integrated into Docker Engine. It allows you to manage a group of Docker nodes as a single virtual system, simplifying the deployment and scaling of containerized applications.
This guide will walk you through installing Docker Swarm across Ubuntu 22.04 servers.
What You Need
Before you begin, ensure the following:
- Three Ubuntu 22.04 servers: one for the Swarm Manager and two as Worker Nodes.
- A non-root user with sudo privileges on each server.
Initial Setup
Start by configuring the environment on all servers before installing Docker or enabling Swarm features.
Open Required Ports
Docker Swarm relies on specific network ports for node communication and service traffic. These can be opened using UFW, the default firewall tool on Ubuntu.
Allow SSH access and activate UFW:
sudo ufw allow OpenSSH
sudo ufw enableNext, open a range of ports (30000–35000) for services:
sudo ufw allow 30000:35000/tcpOpen the essential ports used by Docker Swarm:
for ports in 2377/tcp 7946/tcp 7946/udp 4789/udp
do
sudo ufw allow $ports
doneFinally, apply the changes and confirm the firewall status:
sudo ufw reload
sudo ufw statusAdd the Docker Repository
Now, configure your servers to install Docker from the official Docker repository.
Install essential dependencies:
sudo apt install apt-transport-https ca-certificates curl gnupg lsb-release -yAdd Docker’s GPG key and repository:
sudo install -m 0755 -d /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg
sudo chmod a+r /etc/apt/keyrings/docker.gpg
echo
"deb [arch=\"$(dpkg --print-architecture)\" signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu
\"$(. /etc/os-release && echo \"$VERSION_CODENAME\")\" stable" |
sudo tee /etc/apt/sources.list.d/docker.list > /dev/nullUpdate the package index:
sudo apt updateInstall Docker Engine
Now you can install Docker Engine on all servers:
sudo apt-get install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-pluginOnce installed, verify Docker is enabled and running:
sudo systemctl is-enabled docker
sudo systemctl status docker(Optional) Allow Docker Commands for Non-Root Users
To manage Docker as a non-root user, add your user to the Docker group:
sudo usermod -aG docker usernameSwitch to the user and test with a sample container:
su - username
docker run hello-worldInitialize Docker Swarm
Use one server as the Swarm Manager to initialize the cluster.
Set up Swarm mode:
docker swarm init --advertise-addr 192.168.5.30 --default-addr-pool 10.20.0.0/16Check the Swarm status:
docker infoView current nodes:
docker node lsAdd Worker Nodes
To add a worker, generate a token:
docker swarm join-token workerRun the provided join command on each worker node:
docker swarm join --token SWMTKN-... 192.168.5.30:2377Back on the manager node, verify the full node list:
docker node lsDeploy a Service to the Swarm
Create a test service (e.g., using Nginx):
docker service create --replicas 1 --name test-nginx -p 30001:80 nginx:alpineView service details:
docker service inspect test-nginx
docker service inspect --pretty test-nginxCheck service status:
docker service ls
docker service ps test-nginxTest service access:
curl 192.168.5.30:30001
curl -I 192.168.5.30:30001Scale the Service
Scale the service across nodes:
docker service scale test-nginx=3Check the service on all nodes:
docker service ps test-nginxFrom each worker node:
docker ps
curl 192.168.5.31:30001Clean Up
To remove the service and image:
docker service rm test-nginx
docker service ps
docker rmi nginx:alpine
docker imagesConclusion
You’ve successfully set up Docker Swarm on Ubuntu 22.04, deployed a sample service, scaled it, and performed basic clean-up. This foundational knowledge prepares you for managing scalable, containerized applications with Docker Swarm.
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