Jenkins is an open-source automation server designed to streamline the software development process by supporting Continuous Integration (CI) and Continuous Delivery (CD). In simple terms, Jenkins enables code to be built, tested and deployed faster and more reliably by automating repetitive tasks. It is one of the most widely used tools in DevOps environments and helps teams improve software quality and achieve faster release cycles.
Originally, Jenkins was developed as a fork of Hudson in 2011 after conflicts arose over the future of the project. Since then, Jenkins has become one of the most popular CI/CD tools with an active community, thousands of plugins and broad support for various programming languages and frameworks.
Whether you are a start-up looking to run faster iterations or a large company with complex development environments, Jenkins provides the flexibility and power to accelerate software development.
Jenkins is used by thousands of companies worldwide to streamline software development processes. But why do so many organizations choose this tool? Here are some key benefits:
Jenkins allows development teams to automate every part of their software lifecycle. From building and testing code to deploying it to production environments-everything can be automated. This minimizes human error and significantly increases the speed of releases.
One of Jenkins' greatest strengths is its massive range of plugins. Whether you're working with GitHub, Docker, Kubernetes, or cloud providers such as AWS and Azure-Jenkins integrates effortlessly with virtually every development tool and platform. As a result, Jenkins can be easily adapted to the specific needs of a project or organization.
Because Jenkins is open-source, there are no licensing fees involved. Moreover, you benefit from a large community that continuously develops new features and plugins. Problems are solved quickly and there is an abundance of documentation and tutorials available.
Whether you're managing a small project or have complex, large-scale systems, Jenkins is scalable. Thanks to its distributed architecture, you can easily add additional agents and distribute tasks across multiple machines for optimal performance.
Jenkins is written in Java, so it runs on virtually any operating system, such as Windows, macOS, and Linux. This makes it accessible to various development environments.
Comparison with other CI/CD tools
Although several alternatives exist, such as GitLab CI/CD, CircleCI and Bamboo, Jenkins stands out for its flexibility, extensive plugin ecosystem and huge community. For organizations desiring customization and complete control, Jenkins often remains the first choice.
To work effectively with Jenkins, it is important to understand the basic concepts. These components form the core of how Jenkins functions and how you can use it for your automation needs.
The Jenkins Controller is the brains of the operation. It coordinates tasks, manages configuration and distributes commands to agents (slaves) for execution. The controller also contains the user interface where you set pipelines and view results.
Important: The term “Master” has been replaced with “Controller” to use more inclusive terminology.
Agents perform the actual tasks, such as building, testing and deploying code. You can configure multiple agents to distribute tasks and balance the workload. This is especially useful for large projects with multiple builds running simultaneously.
A node is any machine on which Jenkins tasks can run. The controller itself is a node, but you can add external agents to run builds on other machines. This makes Jenkins extremely flexible and scalable.
A job (or project) is a task that Jenkins executes. It can range from a simple “build and test” job to complex multi-stage CI/CD pipelines. Jobs can be started manually or automatically triggered by code updates, for example.
A pipeline is a series of steps performed to build, test and deploy software. Jenkins supports “Pipeline as Code” through the Jenkinsfile, which allows developers to manage their CI/CD workflows directly in the codebase. This enables versioning of the pipeline and keeps the development process transparent and reproducible.
Example of a simple Jenkinsfile:
pipeline {
agent any
stages {
stage('Build') {
steps {
echo 'Building the application...'
}
}
stage('Test') {
steps {
echo 'Running tests...'
}
}
stage('Deploy') {
steps {
echo 'Deploying to production...'
}
}
}
}Jenkins' strength lies not only in its flexibility, but also in the scalable architecture it offers. Jenkins uses a Controller-Agent model, which allows developers to easily run builds on different machines and environments. This allows for more efficient use of resources and faster turnaround of CI/CD processes.
The Jenkins Controller manages the overall operation of Jenkins. It is responsible for receiving commands, scheduling tasks, managing users and coordinating agents. The actual execution of tasks usually occurs on Jenkins Agents.
Controller → Controls coordination and contains the web interface.
Agents → Perform the actual tasks, such as builds, tests, and deployments.
Benefit: This model ensures that heavy processes do not run on the controller itself, keeping it responsive.
By using multiple agents, you can distribute builds across different machines. This not only improves performance, but also allows you to test builds in different environments (e.g., Linux, Windows, and macOS).
Example scenario:
Suppose you have a large project consisting of multiple microservices. You can then deploy a separate agent for each microservice so that builds are executed in parallel.
Jenkins supports load balancing via Jenkins Agents, which allows you to easily handle peak load. This makes Jenkins suitable for both small teams and large enterprises.
Example of a Jenkins architecture:
+--------------------+
| Jenkins Controller|
+--------------------+
|
+-------------+-------------+
| |
+----------------+ +----------------+
| Jenkins Agent 1| | Jenkins Agent 2|
+----------------+ +----------------+
(Linux) (Windows)In this setup, the controller distributes tasks between agents depending on their availability and compatibility.
One of the advantages of Jenkins is that installation is relatively simple. Here's how to get started quickly.
Requirements:
Java Development Kit (JDK) 8 or higher.
A server or local machine (Windows, macOS, or Linux)
Installation steps:
Download Jenkins from the official website (jenkins.io).
Install Jenkins on your system:
Windows: Use the MSI installer.
macOS: Use Homebrew (brew install jenkins-lts).
Linux: Use a package manager such as apt or yum.
Launch Jenkins:
Windows/macOS: Jenkins starts automatically.
Linux: Start Jenkins manually via:
sudo systemctl start jenkinsAccessing Jenkins: Open your browser and go to http://localhost:8080. Here you will be asked to enter an initial admin password. You can find this password in the file /var/lib/jenkins/secrets/initialAdminPassword.
Enter the initial admin password.
Select “Suggested Plugins” to automatically install the recommended plugins.
Create an admin account.
Set up Jenkins for use by completing basic settings.
Plugins are the heart of Jenkins and make the tool extremely flexible. During initial configuration, you can immediately install recommended plugins. Want to add more later? Then go to:
Manage Jenkins → Manage Plugins → AvailablePopular plugins:
GitHub Integration: For integration with GitHub repositories.
Pipeline Plugin: For setting up Jenkins Pipelines.
Docker Pipeline: For integration with Docker containers.
Blue Ocean: A visual interface for managing pipelines.
Now that Jenkins is installed and configured, you can build your first pipeline.
Steps:
Go to Dashboard → New item → Pipeline.
Give your pipeline a name.
Select Pipeline as the project type.
Under “Pipeline script” add the following:
pipeline {
agent any
stages {
stage('Build') {
steps {
echo 'Building the application...'
}
}
stage('Test') {
steps {
echo 'Running tests...'
}
}
stage('Deploy') {
steps {
echo 'Deploying application...'
}
}
}
}Click Build Now and view the result.
Jenkins' strength lies in its use of pipelines. These allow you to automate entire CI/CD processes, from code building and testing to production deployments.
Declarative Pipeline:
The most commonly used form, easier to read and maintain. Example:
pipeline {
agent any
stages {
stage('Build') {
steps {
echo 'Building...'
}
}
stage('Test') {
steps {
echo 'Testing...'
}
}
stage('Deploy') {
steps {
echo 'Deploying...'
}
}
}
}Scripted Pipeline:
More flexible, but more complex. Uses full Groovy syntax. Example:
node {
stage('Build') {
echo 'Building...'
}
stage('Test') {
echo 'Testing...'
}
stage('Deploy') {
echo 'Deploying...'
}
}A Jenkinsfile defines the complete CI/CD pipeline and is stored in the root of your repository.
pipeline {
agent any
environment {
DEPLOY_ENV = 'production'
}
stages {
stage('Build') {
steps {
sh 'npm install'
}
}
stage('Test') {
steps {
sh 'npm test'
}
}
stage('Deploy') {
steps {
sh 'npm run deploy -- --env $DEPLOY_ENV'
}
}
}
}Benefits of a Jenkinsfile:
Version control along with the code
Transparency about the build process
Reusability for different projects
In a pipeline, it is important to build in error handling. Jenkins supports timeouts, retries, and error handling:
pipeline {
agent any
stages {
stage('Example') {
steps {
retry(3) {
sh 'some-flaky-command'
}
}
}
}
}Jenkins can send notifications via email, Slack, or other communication tools on successful or failed builds. For example, add a Slack notification after a successful deployment:
post {
success {
slackSend(channel: '#ci-cd', message: 'Deployment was successful!')
}
}An important aspect of Jenkins is managing security and access rights within the environment. Because Jenkins often serves as a central tool within CI/CD environments, it is essential to secure sensitive data and access.
By default, Jenkins provides simple user authentication, but for larger teams it is recommended to use Role-Based Access Control (RBAC).
Admin users: Manage the entire Jenkins instance.
Developers: May manage pipelines and run builds.
Viewers: Have read-only privileges and can view build results.
How do you set up RBAC?
Go to Manage Jenkins → Manage Plugins and install the Role-based Authorization Strategy plugin.
Set user roles via Manage Jenkins → Configure Security.
Assign permissions at the project level for maximum control.
Jenkins provides a Credential Manager that allows you to securely store sensitive data such as API keys, passwords, and SSH keys.
Benefits:
Sensitive data is never stored directly in Jenkinsfiles.
Access to credentials can be restricted based on user rights.
Example of using credentials in a Jenkinsfile:
pipeline {
agent any
stages {
stage('Deploy') {
steps {
withCredentials([string(credentialsId: 'API_KEY', variable: 'apiKey')]) {
sh 'curl -H "Authorization: Bearer $apiKey" https://api.example.com/deploy'
}
}
}
}
}Use HTTPS to encrypt traffic between Jenkins and users.
Restrict access to the Jenkins server with firewalls or VPNs.
Keep Jenkins up-to-date to prevent security breaches.
Use two-factor authentication (2FA) whenever possible.
One of Jenkins' greatest strengths is its ability to integrate with almost any tool or service through a wide range of plugins.
GitHub Plugin: Links Jenkins directly to your GitHub repositories.
Docker Plugin: Allows you to run builds in containers.
Pipeline Plugin: For setting up complex CI/CD workflows.
Slack Notification Plugin: Sends automatic notifications to Slack channels.
Blue Ocean: Provides a visual interface for managing pipelines.
Jenkins works effortlessly with cloud providers such as AWS, Azure and Google Cloud. Many teams choose to run Jenkins in the cloud for better scalability and less maintenance.
Integration examples:
AWS EC2 Plugin: Automatically creates new agents when additional compute power is needed.
Azure DevOps Plugin: Integrates Azure Repos and Pipelines with Jenkins.
Google Cloud Build Plugin: Enables Jenkins builds to run in Google Cloud.
It is crucial to monitor pipelines and intervene in a timely manner in case of errors. Jenkins provides standard logging and build reports, but can also be extended with external monitoring tools.
Recommended tools:
Prometheus & Grafana: For real-time metrics and dashboards.
ELK Stack (Elasticsearch, Logstash, Kibana): For log management and visualization.
New Relic or Datadog: For in-depth performance monitoring.
Jenkins X is the cloud-native variant of Jenkins, designed to support modern applications in Kubernetes environments. Whereas classic Jenkins is primarily suited for on-premises and traditional CI/CD, Jenkins X focuses on automation in the cloud.
Jenkins X provides optimized CI/CD processes for container-based and microservices architectures. It uses Kubernetes, Helm and GitOps principles to simplify management of infrastructure and software deployments.
Microservices architectures
Cloud-native projects
Teams using Kubernetes
Rapid scalability and automated infrastructure
Although Jenkins is one of the most popular CI/CD tools, it has both strengths and some concerns. Below, we list the main advantages and disadvantages to provide a balanced view.
Advantages of Jenkins
Open-source and free
Jenkins is completely open-source and free to use. There are no licensing fees, which makes it attractive to both startups and large enterprises.
Flexibility and extensibility.
With thousands of plugins available, Jenkins can be easily adapted to virtually any development environment. Whether you're working with Git, Docker, Kubernetes or cloud providers, Jenkins integrates seamlessly.
Large community and rich documentation
Jenkins has an active global community. As a result, there is extensive documentation, numerous tutorials are available, and common issues are quickly resolved.
Platform independence
Jenkins runs on virtually every operating system that supports Java, including Windows, macOS, and Linux. As a result, it can be easily integrated into existing infrastructures.
Full CI/CD support.
Jenkins supports the full CI/CD process: from code building and testing to final deployment. This makes it a one-stop solution for software development.
Disadvantages of Jenkins
Complexity and learning curve.
For beginners, Jenkins can be intimidating. Setting up advanced pipelines or managing complex builds requires in-depth knowledge.
Maintenance-intensive
Using many plugins can increase the maintenance burden. Plugins need to be updated regularly and incompatibilities can occur after Jenkins updates.
User interface is dated
Although Jenkins' functionality is powerful, many users find the default interface less intuitive. The Blue Ocean plugin offers a more modern alternative, but requires additional installation.
Security risks with misconfiguration
Because Jenkins often accesses sensitive data and production environments, misconfiguration is a security risk. Regular maintenance and following best practices are therefore essential.
Several problems can arise when using Jenkins, especially when configuration becomes more complex. Here are some of the most common pitfalls and how to avoid them.
Build failures due to incorrect configuration.
Cause: Wrong path references, incorrect build environments or missing dependencies.
Solution:
Check the build log carefully.
Use a Jenkinsfile to standardize build processes.
Test the pipeline first in a staging environment.
Long build times
Cause: Inefficient scripts, too many parallel processes or resource constraints.
Solution:
Use caching and minimize dependencies.
Add additional agents for parallel builds.
Optimize test cases and avoid redundant steps.
Problems with plugins
Cause: Outdated or incompatible plugins can lead to system errors.
Solution:
Keep plugins up-to-date.
Check compatibility before updating Jenkins itself.
Use the Plugin Manager to quickly identify problematic plugins.
Security leaks due to incorrect permissions
Jenkins simplifies and automates software development processes by supporting Continuous Integration (CI) and Continuous Delivery (CD). This enables faster releases, higher code quality and a streamlined development process.
Jenkins supports both CI (Continuous Integration) and CD (Continuous Delivery/Deployment). It allows developers to continuously build, test and deploy code directly to production environments.
Before Jenkins, tools such as Hudson (Jenkins' predecessor) and CruiseControl were widely used. Jenkins originated as a fork of Hudson and grew to become the most popular CI/CD tool thanks to its active community and wide support.
