Execute commands inside Docker container in Jenkins

This guide will show you how to perform some build steps or command inside a Docker container, using Declarative Pipelines in Jenkins.

Imagine you have to build a special application, which requires lots of libraries and dependencies, at specific versions, and you can't install them on your Jenkins machines.

How to build it?

Using a Docker container!

First of all, you need to install the Docker Pipeline plugin:

https://plugins.jenkins.io/docker-workflow/

To use the plugin with a Declarative pipeline, add this stage:

stage('Run command inside a container') {

  steps {

    script {

      withDockerContainer("my-custom-image:1.0") {

        echo 'This command is executed inside the container!'

      }

    }

  }

}

Takes the image my-custom-image:1.0 which must already have been pulled locally, and starts a container based on that image. Runs all nested steps inside that container. The workspace is mounted read-write into the container.

Example with Python:

pipeline {

  agent any 

  stages {

   

    stage('Clone sources') {

      steps {

        git credentialsId: 'git-creds', url: 'https://git.example.com/myrepo.git'

      }        

    }

    //build a Docker image with a Dockerfile from sources

    stage("Build Docker images") {

      steps {

        script {

          docker_image_dev = docker.build("my-custom-python:3.6")

        }

      }

    }

    //Run tests inside a container based on previous image

    stage('Run Tests: Coverage') {

      steps {

        script {

          withDockerContainer("my-custom-python:3.6") {

            sh 'pwd'

            sh 'pylint source | tee test/results/pylint.txt'

          }

        }

      }

    }

  }

}