Jenkins¶

Jenkins is a CI/CD service.

There is an official image for this service that we'll use: jenkins/jenkins.

Pre-Installation¶

We'll create a folder in the main user's home where all the service's data will be saved.

mkdir ~/services/development/jenkins

Agent Dockerfile¶

We'll use a custom Dockerfile to create an agent that has the necessary dependencies installed.

First, create a new folder for the agent's data.

mkdir agent

Then, we'll generate an SSH key that Jenkins will use to connect to the agent.

ssh-keygen agent/jenkins_agent_key

Now, run the following command:

id

And check for the ID of the docker group. In this case, this value is 998.

Next, we'll add a Dockerfile for the agent:

FROM jenkins/ssh-agent:jdk11

USER root

RUN groupadd -g 998 docker

RUN apt-get update -qq
RUN apt-get install -qqy apt-transport-https ca-certificates curl gnupg2 software-properties-common
RUN curl -fsSL https://download.docker.com/linux/ubuntu/gpg | gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg
RUN echo \
  "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/debian \
  $(lsb_release -cs) stable" | tee /etc/apt/sources.list.d/docker.list > /dev/null
RUN apt-get update -qq && apt-get -y install docker-ce

RUN usermod -aG docker jenkins

Make sure to add the generated private key as a Credential inside Jenkins as an SSH Username with private key with jenkins as the username.

Docker Compose¶

Jenkins will be run using Docker Compose. The content of the docker-compose.yml file is as follows:

services:
  web:
    image: jenkins/jenkins:lts
    restart: unless-stopped
    networks:
      default:
      proxy_external:
        aliases:
          - jenkins
    volumes:
      - ./data:/var/jenkins_home
    environment:
      TZ: America/Guayaquil
    labels:
      traefik.enable: true
      traefik.docker.network: proxy_external
      traefik.http.routers.jenkins.rule: Host(`subdomain.example.com`)
      traefik.http.routers.jenkins.entrypoints: public
      traefik.http.routers.jenkins.service: jenkins@docker
      traefik.http.services.jenkins.loadbalancer.server.port: 8080

  agent:
    build: ./agent/
    restart: unless-stopped
    depends_on:
      - web
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
    environment:
      TZ: America/Guayaquil
      JENKINS_AGENT_SSH_PUBKEY: PUBKEY_HERE

networks:
  proxy_external:
    external: true

Note

Make sure to replace PUBKEY_HERE with the content of the public key generated previously.

Note

Replace subdomain.example.com with the domain name where your service will be accessible from.

Reverse Proxy¶

This service is exposed by a reverse proxy. More specifically, it is using Traefik.

For this reason, you will see that this service has:

A directive to connect it to the proxy_external external network.
A container alias for the proxy_external network.
A number of labels with names starting with traefik.

If you're not using a reverse proxy, feel free to remove these from the docker-compose.yml file. Keep in mind you might need to bind the ports to connect to the service instead.

Running¶

Start up the service with:

docker compose up -d

That's it! The service will auto-start on system startup and restart on failure.