How To Set Up Jenkins 2.0 Master & Slaves On Docker

We can just use the Jenkins Docker official image, or you can just install Jenkins 2.0 normally.

Open up TCP port by adding the following in /etc/default/docker

DOCKER_OPTS="-H tcp://0.0.0.0:4243 -H unix:///var/run/docker.sock"

On Jenkins Master, install Docker Plugin on Master->Manage Jenkins->Manage Plugins
On Master->Manage Jenkins->Cloud configure the communication with Jenkins slave node
Docker URL is the IP of the Slave machine in TCP
Click on Test Connection, if successful will show the Docker version and Docker API version

Have Docker Jenkins Slave images in the slave box
On Master->Manage Jenkins->Manage Plugins->Cloud->Add Docker Template
The SSH credentials to access the Docker Jenkins Slave container is the Jenkins user setup in Dockerfile and Jenkins Master

There are some Docker images that you can use like Docker Slave image , or you can write your own Dockerfile.

Docker image contains a minimum of:

Ubuntu
Java
Jenkins user and password
Git
OpenSSH for Jenkins Master to SSH to Slave machine
Maven, Ruby, etc depends on what your project needs
Version managers like NPM or RVM cannot be installed in Docker due to we cannot “source” files like .bashrc

It is a sshd service running on port 22, therefore in the Dockerfile, you will need:

EXPOSE 22

CMD [“/usr/sbin/sshd”, “-D”]

We restrict Jenkins jobs to run based on the label we give in Docker template
When job runs, Jenkins Master will spin up the Docker image on the Slave machine
When job completes, the Docker image will be terminated
Therefore, we can have multiple Docker images for different types of jobs, Ruby, Maven, NodeJS on a single Slave machine