How to use Jenkins Docker Cloud

Recently, I am working on Jenkins instance migration, this time I started to use Jenkins Docker Cloud insead of use docker { ... } in Jenkinsfile.

Jenkins cloud plugin

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First you need to install Jenkins Docker Cloud plugin https://plugins.jenkins.io/docker-plugin/

Jenkins Docker Cloud is a plugin that allows Jenkins to use Docker containers as build agents.

So you need to config a Docker Host with remote API as follows.

Enable Docker Remote API

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Jenkins controller connects to the docker host using REST APIs. To enable the remote API for docker host, please follow the steps below.

Step 1: Spin up a VM, and install docker on it. You can follow the official documentation for installing docker. based on the Linux distribution you use. Make sure the docker service is up and running.

Step 2: Log in to the server and open the docker service file /lib/systemd/system/docker.service. Search for ExecStart and replace that line with the following.

ExecStart=/usr/bin/dockerd -H tcp://0.0.0.0:4243 -H unix:///var/run/docker.sock

Step 3: Reload and restart docker service.

systemctl daemon-reload
service docker restart

Step 4: Validate API by executing the following curl commands. Replace myhostname with your hostname or IP.

curl http://localhost:4243/version
curl http://myhostname:4243/version

Create custom docker image

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For me, I use launch via JNLP for my custom docker image.

For example, you docker image is based on jenkins/inbound-agent, you can use the following Dockerfile to create your custom image.

FROM jenkins/inbound-agent
RUN apt-get update && apt-get install XXX
COPY your-favorite-tool-here

ENTRYPOINT ["/usr/local/bin/jenkins-agent"]

How to use in Jenkinsfile

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Once you have configed Docker Cloud, you can use it in Jenkinsfile like a normal agent.

For example:

// Jenkinsfile (Declarative Pipeline)
pipeline {
    agent {
        node {
            "docker"
        }
    }
}

Which is does not like if you use docker { ... } directly.

For example of using docker { ... }:

// Jenkinsfile (Declarative Pipeline)
pipeline {
    agent {
        docker { image 'node:22.13.1-alpine3.21' }
    }
    stages {
        stage('Test') {
            steps {
                sh 'node --eval "console.log(process.platform,process.env.CI)"'
            }
        }
    }
}

Here is more details about using Docker with pipeline: https://www.jenkins.io/doc/book/pipeline/docker/

Feel free to comment if you have any questions.

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