Docker Image Build

Learn the concepts, configuration, commands, and practical workflow required to use Docker Image Build in a real Jenkins environment.

What is Docker Image Build?

Docker Image Build in Jenkins is the process of compiling your source code, packaging its runtime environment, dependencies, and configurations into an immutable Docker container image using a standard Dockerfile.

In modern Cloud-Native architectures, this replaces old-school deployment packages (like raw zip, jar, or tar files) with a standard build artifact that runs identically across development, staging, and production clusters.

Visualizing the automated pipeline containerization cycle from application packaging down to registry publication.

Key Concepts

Practical Jenkins Example

Below is a production-ready Declarative Pipeline utilizing the Docker Pipeline plugin syntax to build, validate, and clean up local build caches safely:

pipeline {
    agent any
    






    environment {
        IMAGE_NAME = "my-company/web-app"
        IMAGE_TAG  = "${BUILD_NUMBER}"
    }
    
    stages {
        stage('Checkout Source') {
            steps {
                checkout scm
            }
        }
        
        stage('Build Docker Image') {
            steps {
                script {
                    echo "Starting build for ${IMAGE_NAME}:${IMAGE_TAG}"
                    // Looks for a file explicitly named 'Dockerfile' in root directory
                    appImage = docker.build("${IMAGE_NAME}:${IMAGE_TAG}")
                }
            }
        }
        
        stage('Validate Container') {
            steps {
                script {
                    // Temporarily boots container to verify basics before continuing
                    appImage.inside {
                        sh 'echo "Container built and interior verification checks passed successfully."'
                    }
                }
            }
        }
    }
    
    post {
        always {
            script {
                echo "Executing agent pruning cleanup steps..."
                // Prevents local disk exhaustion on the Jenkins builder agent
                sh "docker rmi ${IMAGE_NAME}:${IMAGE_TAG} || true"
            }
        }
    }
}

Practice Exercise

1. Ensure your targeted Jenkins executor agent has the Docker CLI installed and its system user belongs to the local docker security group.
2. Create a new Pipeline Job in your Jenkins controller and add a basic Dockerfile alongside the Jenkinsfile above to your code repository.
3. Execute a manual **Build Now** run and closely observe the Console Output to track how Jenkins sequences the intermediate cache layers.
4. Log directly into your build machine CLI terminal and run docker images to verify the artifact was compiled cleanly with the correct numerical Jenkins build tag.