Utilize Dockerfile Agent

Overview

Leveraging a Dockerfile agent in Jenkins lets you build a custom Docker image with all the CLI tools your pipeline requires. This approach ensures:

• Consistent environments across builds
• Isolation for each job
• Flexibility to install any SDKs, CLIs, or dependencies

Prerequisites

Step 1: Example with the Standard Node.js Alpine Image

Here’s a simple Jenkinsfile using the official node:18-alpine image:

pipeline {
    agent any
    stages {
        stage('S4 - Standard Node.js Image') {
            agent {
                docker {
                    image 'node:18-alpine'
                    label 'ubuntu-docker-jdk17-node20'
                }
            }
            steps {
                sh 'node -v'
                sh 'npm -v'
                sh 'cowsay -f dragon "Hello from Docker Container"'
            }
        }
    }
}

When executed, the first two commands succeed, but cowsay is missing:

/home/jenkins-agent/.../script.sh: line 1: cowsay: not found

Step 2: Create a Custom Dockerfile

To include cowsay, create Dockerfile.cowsay:

FROM node:18-alpine

RUN apk update && \
    apk add --no-cache git perl && \
    git clone https://github.com/jasonm23/cowsay.git /tmp/cowsay && \
    cd /tmp/cowsay && \
    ./install.sh /usr/local && \
    rm -rf /tmp/cowsay

This Dockerfile:

1. Updates the Alpine package index
2. Installs Git and Perl
3. Clones and installs cowsay
4. Cleans up temporary files

Step 3: Switch to the dockerfile Agent

Update your Jenkinsfile to build the custom image on the fly:

pipeline {
    agent any
    stages {
        stage('S4 - Dockerfile Agent') {
            agent {
                dockerfile {
                    filename 'Dockerfile.cowsay'
                    label 'ubuntu-docker-jdk17-node20'
                }
            }
            steps {
                sh 'node -v'
                sh 'npm -v'
                sh 'cowsay -f dragon "This is running on Docker Container"'
            }
        }
    }
}

Behind the scenes, Jenkins will:

1. Read Dockerfile.cowsay from the workspace
2. Run:

   docker build -t <generated-image-id> -f "Dockerfile.cowsay" .
   

3. Launch a container from the new image and execute your steps

Step 4: Confirm Successful Build

In the Jenkins console you’ll see:

docker build -t 0f559f3f6a2c220b616594d407b50bd36d837f4 -f "Dockerfile.cowsay" .
docker inspect -f '{{.Id}}' 0f559f3f6a2c220b616594d407b50bd36d837f4
v18.20.4
10.7.0
This is running on Docker Container

All commands now succeed, including cowsay.

Links and References

• Jenkins Pipeline Agents
• Dockerfile Reference
• Node.js Official Docker Images
• cowsay GitHub Repository