Jenkins Docker Setup

This repo contains:

• Required docker configurations to setup of Jenkins which is quick and reproducible.
• Jenkins docker installation page provides us with more detailed explaination.
• This repo just convert the same set of instructions into easier portable solution using docker-compose.

Usage:

$ docker-compose up --build
Creating JenkinsDocker ... done
Creating JenkinsServer ... done

JenkinsServer is now accecible at localhost:8080/.

Now Jenkins Server is accessible at localhost:8080.

Details:

The docker-compose.yaml file defines following components:

• Jenkins Network: Defines underlying bridge network.
• Jenkins Server: This is jenkins server container definition.
• Jenkins Docker: A docker:dind container to enable running docker inside docker.

Jenkins Network:

Here we will be setting up the underlying network for the containers to communicate between themself. We create a bridge network with name space as jenkins.

networks:
  jenkins:
    driver: bridge # Defines bridge network to be used by services defined later.

Jenkins Docker:

It is a good practice to run the Jenkins job inside docker containers rather than Jenkins host machine itself.

• This enables us to maintain isolation between multiple Jenkins Pipelines and Jobs.
• Also we ahieve an easily reproducible/debuggable job execution environment setup.

Since this is a Jenkins Server setup running as docker container we would need to setup docker-inside-docker, i.e to be able to run docker commands and containers (JOBS containers) inside another docker container (Jenkins Server Container). This is made possible with using docker:dind container.

Here JenkinsDocker container starts docker-engine and exposes it at address tcp://docker:2376. This address will be used later by JenkinsServer container to bring up Jobs containers.

services:
  jenkins_docker:
    image: docker:dind
    networks:
      jenkins:
        aliases:
          - docker # Defines to use jenkins network defined above also under the alias name `docker`.
    container_name: JenkinsDocker
    privileged: true
    environment:
      - DOCKER_TLS_CERTDIR=/certs
    ports:
      - "2376:2376" # Exposes docker serveer port 2376 to be used by jenkins server container at "tcp://docker:2376".
    volumes:
      - ./jenkins-docker-certs:/certs/client # Docker client certs.
      - ./jenkins-data:/var/jenkins_home # Preserves Jenkins data like job definitions, credentials, build logs, etc.
      - ./extras:/extras # Any extra data or files you want to cache between server restart can be saved here `/extras/`.

Jenkins Server:

As last part of the equation, we would bring up JenkinsSever container using customised image jenkins/jenkins:lts-slim. JenkinsServer is now accecible at localhost:8080/.

services:
  jenkins_server:
    build:
      context: # Build container from the custom Dockerfile defined in the repo.
    networks:
      - jenkins # Use jenkins network defined earlier
    container_name: JenkinsServer
    restart: always
    environment: # Define docker env variable to connect to docker-engine defined in JenkinsDocker container.
      - DOCKER_HOST=tcp://docker:2376
      - DOCKER_CERT_PATH=/certs/client
      - DOCKER_TLS_VERIFY=1
    ports:
      - "8080:8080" # For UI
      - "50000:50000" # For API
    volumes:
      - ./jenkins-data:/var/jenkins_home:rw # Docker client certs.
      - ./jenkins-docker-certs:/certs/client:ro # Preserves Jenkins data like job definitions, credentials, build logs, etc.
      - ./extras:/extras:rw # Any extra data or files you want to cache between server restart can be saved here `/extras/`.

Dockerfile

We have customised docker image jenkins/jenkins:lts-slim in the Dockerfile to

• Include few useful plugins and
• Installed docker cli to be able to build our jobs inside docker containers to maintain isolation.

FROM jenkins/jenkins:lts-slim
USER root
RUN apt-get update && apt-get install -y --no-install-recommends \
       apt-transport-https \
       ca-certificates curl gnupg2 \
       software-properties-common
RUN curl -fsSL https://download.docker.com/linux/debian/gpg | apt-key add -
RUN apt-key fingerprint 0EBFCD88
RUN add-apt-repository \
       "deb [arch=amd64] https://download.docker.com/linux/debian \
       $(lsb_release -cs) stable"
RUN apt-get update && apt-get install -y docker-ce-cli
USER jenkins
RUN jenkins-plugin-cli --plugins blueocean:1.24.3

Other useful components:

$ tree -aL 1
.
├── .dockerignore # Contains file patterns to ignore, while creating docker context
├── .git
├── .gitignore # Ignores docker volume mounts
├── Dockerfile
├── LICENSE
├── Readme.md
├── docker-compose.yaml
├── docker-data
├── extras # extras volume mount
├── jenkins-data # Jenkins build logs, etc volume mount
└── jenkins-docker-certs # docker certs volume mount