jenkins-docker

A small repository with Dockerfile's for Jenkins. It basically gives you a jenkins 2 environment with one ssh enabled jenkins slave with docker and docker-compose, as well as one Gradle builder. There is also a demo project called jenkins-docker-test used for testing and its a good place to start seeing how things are built.

A few things to consider before using this.

• These images share unix:///var/run/docker.sock
• jenkins and jenkins-slave have docker installed
• Security has not been a priority so far, and there are surely unresolved issues here
• To enable Docker Pipeline Plugin containers have to be mounted at /var/jenkins_home since this plugin will try to mount the jenkins virtual path to the actual host path.
• Do not use this in production if you are unsure of the consequences of this!

When running Jenkins locally on the host, make sure Jenkins is part of the docker group to give access to the docker socket.

Notice

These images, if you modify and spawn a lot of containers, will use a lot of disk space.
If you run out, remove stale containers with this command

   docker rm -v $(docker ps -a -q -f status=exited)

Building the images

Building the images is as easy as executing a bash script and providing some basic info, but first you should set up a repository.

Preparing a local repository (if you do not have one)

You should have a local repository running to make life easier for you. This is also a great way of getting to know how docker images work while having the ability to start over when ever you like.

Setting this up is as easy as

docker run -d -p 5000:5000 --restart=always --name registry \
  -v `pwd`/data:/var/lib/registry \
  registry:2

Building the images

All images can be built by the same command if you want to. Just specify the name of your docker group and the repository you want to push images to after they are built.

In the root file of the project you will find a file named build. Use this to build the images. If you see some red text, that is normal, if it fails, however, you can just try again and it should work. If you are building from behind a proxy server, you can add that to the end of the build file.

sh build docker localhost:5000
sh build docker localhost:5000 http://proxy.example.org

If you are greeted with this error after trying to start jenkins

touch: cannot touch ‘/var/jenkins_home/copy_reference_file.log’: Permission denied
Can not write to /var/jenkins_home/copy_reference_file.log. Wrong volume permissions?

do a sudo chown -R 1000 /var/jenkins_home

In certain cases, you will be told that the group id exists, in this case, you can change id of the Docker group or add this to your Dockerfile

RUN delgroup $groupname

Building something

Here is an example job that can be built using the provided Gradle builder. Replace localhost:5000 with the path to your repository and it should build. It will not do more than build for now.

node('docker-slave') {
    docker.image('localhost:5000/gradle').inside {
        stage 'Checkout from git'
        git 'https://github.com/scav/jenkins-docker-test.git'
        stage 'Running tests'

        sh 'gradle clean build'
    }
}

Important if you are runnig from a Jenkinsfile you will be greeted with the following message:

org.jenkinsci.plugins.scriptsecurity.sandbox.RejectedAccessException: Scripts not permitted to use new org.jenkinsci.plugins.docker.commons.credentials.DockerRegistryEndpoint java.lang.String java.lang.String

This is because you are executing scripts from git and not internally by a user who can create jobs. You solve this by going to Manage Jenkins » In-process Script Approval where you can approve this action and it will work.

Notes

Some final notes, information or gotchas.

Plugins

The plugins.txt file is rather big, I just took everything from my jenkins install (used to make this) and dumped it into that file.

Todo

In no particular order...

• Add plugins.txt to jenkins/Dockerfile
• Actually build something and push
• Docker Compose
• Some kind of automatic IP sharing of jenkins -> slaves
• Better bash scripts
• Security
• More slaves