How to Run Jenkins on Ubuntu with Docker Compose

Introduction

Jenkins is an open-source tool written in Java to set up continuous integration and deployment pipelines (CI/CD pipelines) for faster software delivery. It is the main part of Software Development Life Cycle automation. This guide describes the step-by-step procedure of setting up Jenkins on a Vultr Ubuntu instance using Docker Compose.

Prerequisites

• A fresh Vultr Ubuntu 20.04 or 18.04 cloud instance
• Docker and Docker Compose installed on the server

Writing Docker Compose for Jenkins

First, create a jenkins-compose directory and a new file docker-compose.yml inside the directory.

$ mkdir jenkins-compose

$ cd jenkins-compose

$ touch docker-compose.yml

Now open the newly created file with your favorite editor.

$ nano docker-compose.yml

Copy the following script into the docker-compose.yml file.

version: '3.8'
services:
  jenkins:
    container_name: jenkins
    restart: always
    image: jenkins/jenkins:lts
    ports:
      - 8080:8080
    volumes:
      - jenkins-home:/var/jenkins_home

volumes:
  jenkins-home:

The syntax of the compose file:

version: ‘3.8’

This version describes the Docker Compose file format for version 3.8. Using some other version for this Docker Compose file may not work.

services:

The services section includes configuration for different docker containers in a single Docker Compose file.

  jenkins:
    container_name: jenkins
    restart: always
    image: jenkins/jenkins:lts
    ports:
      - 8080:8080
    volumes:
      - jenkins-home:/var/jenkins_home

This section includes the configuration for the Jenkins docker container like container name, restart policy, image to be used for the container, port, and volume mappings.

The restart: always option in the compose file ensures that the Jenkins container remains up even after a reboot.

volumes:
  jenkins-home:

The volumes section creates a new volume used inside the Docker Compose.

After writing the compose file for Jenkins, enable and start the docker service. Enabling the service automatically starts the Docker service on system reboot.

$ sudo systemctl enable docker.service

$ sudo systemctl start docker.service

After writing the Docker Compose file for Jenkins server, use the following command to run it.compose.

$ docker-compose up -d

It pulls the Jenkins image from Docker Hub and starts the container. Use the following command to check if the container is running.

$ docker-compose ps

Configure SSL Certificates for Jenkins

To access the Jenkins server on a secure protocol (HTTPS), install the Nginx server, configure SSL certificates for Nginx, and proxy the traffic to the Jenkins server.

Install Nginx.

# apt install nginx -y

Edit your Nginx configuration file.

# nano /etc/nginx/conf.d/default.conf

Copy the following configurations in the file.

server {
  server_name example.com www.example.com
}

Follow this guide to generate SSL Let's Encrypt certificates for Nginx server. It automatically adds the SSL configuration to the /etc/nginx/conf.d/default.conf file. Open the configuration file.

# nano /etc/nginx/conf.d/default.conf

Add the following configurations to proxy the traffic to the Jenkins server.

location / {
  proxy_pass http://127.0.0.1:8080;
  proxy_set_header Host $host;
  proxy_set_header X-Forwarded-For $remote_addr;
}

The final configuration file looks like this.

server {
  server_name example.com www.example.com;


    listen 443 ssl; # managed by Certbot
    ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem; # managed by Certbot
    include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
    ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot

    location / {
      proxy_pass http://127.0.0.1:8080;
      proxy_set_header Host $host;
      proxy_set_header X-Forwarded-For $remote_addr;
    }


}
server {
    if ($host = www.example.com) {
        return 301 https://$host$request_uri;
    } # managed by Certbot


    if ($host = example.com) {
        return 301 https://$host$request_uri;
    } # managed by Certbot


  server_name example.com www.example.com;
    listen 80;
    return 404; # managed by Certbot
}

Configure Firewall

To secure your Vultr server, configure the firewall to allow traffic only on ports 80, 443, and 22 (SSH port). You can use the OS firewall or Vultr firewall, or both to secure your server. Use this guide to configure the Vultr Firewall.

To configure the OS firewall, follow these steps:

Install the OS firewall using the following command.

# apt install ufw 

Block all the incoming and allow all the outgoing traffic.

# ufw default deny incoming
# ufw default allow outgoing

Allow traffic from specific ports.

# ufw allow ssh
# ufw allow http
# ufw allow https

NOTE: Before enabling the OS firewall, make sure the SSH port is not blocked; otherwise, you will not be able to access your server.

Now enable the firewall.

# ufw enable

Check the firewall status.

# ufw status

Test Jenkins Server

After running the Jenkins server, access the server on port 443 of your Vultr server like https://www.example.com/. It will ask for the Administrator password.

Use the following command to read the Administrator password from the container.

$ docker exec -it jenkins cat /var/jenkins_home/secrets/initialAdminPassword

Now it will ask whether to install some suggested plugins or not.

Install the suggested plugins.

Now it will ask for the details for the first admin user.

After setting up the admin user, now Jenkins server is ready to set up CI/CD pipelines.

Conclusion

Compose is a tool used to configure and run containerized applications. It makes it easier to deploy a containerized application to the server. This guide explained how to run the Jenkins server with Docker Compose on a Vultr Ubuntu instance.