How to Use Docker in Jenkins Pipeline: Simple Guide

To use docker in a Jenkins pipeline, you can run Docker commands inside a sh step or use the docker pipeline plugin for better integration. Make sure Jenkins has Docker installed and the user running Jenkins has permission to access Docker.

Syntax

In a Jenkins pipeline, Docker commands can be run inside a sh step for scripted pipelines or using the docker pipeline plugin for declarative pipelines.

• sh step: Runs shell commands, including Docker CLI commands.
• docker plugin: Provides methods like docker.image() to pull and run containers.

groovy

pipeline {
  agent any
  stages {
    stage('Run Docker Command') {
      steps {
        sh 'docker ps'
      }
    }
  }
}

Example

This example shows a Jenkins declarative pipeline that pulls a Docker image and runs a container to print 'Hello from Docker!'. It uses the docker pipeline plugin for clean syntax.

groovy

pipeline {
  agent any
  stages {
    stage('Run Docker Container') {
      steps {
        script {
          docker.image('alpine').inside {
            sh 'echo Hello from Docker!'
          }
        }
      }
    }
  }
}

Output

Hello from Docker!

Common Pitfalls

Common mistakes when using Docker in Jenkins pipelines include:

• Jenkins user lacking permission to run Docker commands, causing permission denied errors.
• Not having Docker installed on the Jenkins agent or master node.
• Using docker commands without the pipeline plugin, leading to complex shell scripts.
• Forgetting to wrap Docker commands inside sh or script blocks in declarative pipelines.

groovy

pipeline {
  agent any
  stages {
    stage('Wrong Usage') {
      steps {
        // This will fail because docker commands need to be inside sh or script
        // docker.image('alpine').inside {
        //   sh 'echo Hello'
        // }
        sh 'docker ps'
      }
    }
  }
}

Quick Reference

Concept	Usage	Notes
Run Docker CLI	sh 'docker '	Simple but less integrated
Use Docker Plugin	docker.image('name').inside { ... }	Cleaner, recommended for declarative pipelines
Permissions	Ensure Jenkins user in docker group	Avoid permission denied errors
Agent Setup	Docker installed on Jenkins node	Required to run Docker commands
Pipeline Type	Scripted or Declarative	Use script block for scripted commands in declarative pipelines

Key Takeaways

Run Docker commands inside sh steps or use the Jenkins Docker pipeline plugin for better integration.

Ensure Docker is installed and Jenkins user has permission to run Docker commands.

Use docker.image().inside for clean container execution in declarative pipelines.

Wrap Docker commands inside script blocks when using declarative pipelines.

Check Jenkins agent setup to avoid common permission and installation issues.