CODEWITHSUNDEEP
dockerjenkinsjenkins-pipeline
Ganesh Satpute
Ganesh Satpute

Reputation: 3951

Is Jenkins running command inside container?

I want to run the Jenkins pipeline inside a docker container, like running all the tests, doing sonar scanning, etc.

This is what my pipeline looks like. 

pipeline {  
    agent {
        docker { 
            image 'node:10-alpine' 
            args '-u root:root'
        }
    }

    stages {
        stage('Checkout') {
            steps {
                sh 'node --version; cat /proc/1/cgroup; touch /root/my_file' 
                checkout(...)
            }
        }
        stage('Run Unit Tests') {
            steps {
                sh ''' 
                    npm install --unsafe-perm
                '''
           }
      }
    }
}

Now as an output of this, I see following logs in the console 

+ cat /proc/1/cgroup
...
2:freezer:/docker/eeea802143ce0f1b4047650956e58624a0c38a5fbc601f189755a381dcf9c271
1:name=systemd:/docker/eeea802143ce0f1b4047650956e58624a0c38a5fbc601f189755a381dcf9c271

Which means the command runs in the docker container. Also, I can see /root/my_file does not exist on the host.

Now, further, I see following output 

+ npm install --unsafe-perm
> [email protected] install /home/jenkins/mount-dir/workspace/test-docker-pipeline/api/node_modules/libpq
> node-gyp rebuild

Now, here I see that the log mentions a directory that is present on the host.

I'm now confused, where my pipeline is executing, inside container or insider Jenkins? If either of the case, why I am seeing the contradictory log statement?

Upvotes: 1

Views: 1278

Answers (2)

A.K.
A.K.

Reputation: 989

All your commands are run inside the container as you expect. So everything is fine.

What Jenkins is doing is to bind-mount the Workspace folder at the same location inside the Container. If you check your jobs console Output you should find something like:

Docker 1 does not seem to be running inside a container
$ docker run -t -d -u 1002:1002 -w /home/jenkins/build/workspace/<my-project> -v   /home/jenkins/build/workspace/<my-project>:/home/jenkins/build/workspace/<my-project>:rw,z -v /home/jenkins/build/workspace/<my-project>@tmp:/home/jenkins/build/workspace/<my-project>@tmp:rw,z    $ docker top 8948be0b380b033f20cd8c27647b88719b47a237f839513ebf66a9693b4c2975 -eo pid,comm
Running in /home/jenkins/build/workspace/<my-project>

The -v option is doing the bind-mount of your Workspace Folder from your host into the same location inside the running container. For more information on Docker's bind-mlunt capability please see the official documentation at: https://docs.docker.com/storage/bind-mounts/

Edit: Since Pipeline 2.5 Jenkins Pipeline has native support for Docker Images. Therefor no Docker Pipeline Plugin needed anymore.

Upvotes: 1

Ganesh Satpute
Ganesh Satpute

Reputation: 3951

After carefully looking at the logs of the pipeline job I saw this line 

$ docker run -t -d -u 1001:1001 -u root:root -w /home/jenkins/mount-dir/workspace/test-docker-pipeline -v /home/jenkins/mount-dir/workspace/test-docker-pipeline:/home/jenkins/mount-dir/workspace/test-docker-pipeline:rw,z -v /home/jenkins/mount-dir/workspace/test-docker-pipeline@tmp:/home/jenkins/mount-dir/workspace/test-docker-pipeline@tmp:rw,

Which is a docker run command used by Jenkins. Here Jenkins mounts the directory in the exactly same path. So when we see reference /home/jenkins/mount-dir/... in logs it's indeed run in Docker container but actual storage is mounted on the Jenkins host.

Upvotes: 0

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