CI • docker • jenkins

The Jenkins 2.0 alpha version is a good opportunity for me to finally spend some time with Docker (some two years late, shame on me). So, this is a short documentation of my steps to a dockerized Jenkins 2.0 instance on my Windows 10 box:

Lesson #1: Run Jenkins in a Docker container (without prior Docker knowledge)

  1. Install Docker as described at https://docs.docker.com/windows/ (I’m using Docker Toolbox v1.10.3). This also installs VirtualBox and creates a virtual Linux machine (Docker uses a Linux virtualization feature that is not available on Windows)
  2. Launch the “Docker Quickstart Terminal”
  3. Locate the Jenkins 2.0 image at the Docker hub (The official Jenkins repo contains no alpha versions)
  4. Create and start a new Jenkins container with docker run -p 8080:8080 -p 50000:50000 jenkinsci/jenkins:2.0-alpha-3. After the image download, Jenkins initializes and starts within 20 seconds. Wait until the security token appears at the console.
  5. Open http://192.168.99.100:8080/ in a browser (find out the real IP address with docker-machine ip) and enter the security token. Welcome to Jenkins 2.0 :-)
  6. Now remove the container again
docker ps
docker inspect <id>
docker stop <id>
docker rm <id>

Lesson #2: Write the Jenkins workspace to a local (Windows) directory

cd ~
mkdir docker
mkdir docker/jenkins
docker run --name jenkins2 -p 8080:8080 -p 50000:50000 -v ~/docker/jenkins:/var/jenkins_home jenkinsci/jenkins:2.0-alpha-3

The first startup takes about 7 minutes(!), the following startup is much faster (which means that writing to the host filesystem is pretty slow on Windows)

Notes:

  • Out of the box, only c:\Users is available for mounting
  • Even local (Windows) filenames are case sensitive.
  • see https://docs.docker.com/engine/userguide/containers/dockervolumes/
  • using the --name option, it is easier to reference the container later:
docker start jenkins2
docker exec -i -t jenkins2 bash
docker stop jenkins2
docker rm jenkins2

Lesson #3: Write the Jenkins workspace to a data volume (for better performance)

docker run --name jenkins2 -p 8080:8080 -p 50000:50000 -v jenkins-data:/var/jenkins_home jenkinsci/jenkins:2.0-alpha-3
docker volume ls
docker volume inspect jenkins-data

AFAIK it is not possible to directly access the files inside the data container. But we can always launch another container, mount both the data volume and a local directory, and copy the files:

docker run -v jenkins-data:/var/jenkins_home -v ~/docker:/backup debian tar czf /backup/jenkins-backup.tgz /var/jenkins_home
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