Introduction to Jenkins

Hello! In this lesson, we'll dive into Jenkins, a powerful open-source automation server. It's a cornerstone for implementing Continuous Integration (CI) and Continuous Delivery (CD) in modern software development.

Jenkins helps automate the non-human part of the software development process, with continuous integration and facilitating continuous delivery.

Jenkins brings a lot of benefits to your development workflow:

• Automates Tasks: It takes over repetitive tasks like building, testing, and deploying your code.
• Extensive Plugin Ecosystem: Supports thousands of plugins, allowing integration with almost any tool in the CI/CD chain.
• Continuous Feedback: Provides immediate feedback on code changes, helping teams catch issues early.
• Scalable: Can be distributed across multiple machines to handle large workloads.

There are several ways to install Jenkins, but for a quick start, especially for local development or learning, using Docker is often the simplest and most recommended approach.

Other methods include native package installations (for Debian/Ubuntu, Red Hat/CentOS) or deploying a WAR file.

Let's get Jenkins running using a Docker container. This command pulls the latest Long Term Support (LTS) Jenkins image, maps ports, and creates a volume for persistent data.

Run this command in your terminal:

After running the Docker command, Jenkins will start up. You'll need an initial administrator password to unlock it. This password is generated during the first startup.

To retrieve it, you can inspect the container's logs:

Once you have the password, navigate to http://localhost:8080 in your web browser. You'll be greeted by the Jenkins setup wizard.

Paste the administrator password to unlock Jenkins. Then, you'll be prompted to install plugins. Choose 'Install suggested plugins' for a standard setup, which includes essential plugins for common CI/CD tasks.

After creating your first admin user, you'll land on the Jenkins dashboard. This is your central hub for all things Jenkins.

Key areas to notice:

• New Item: To create new automation jobs.
• Manage Jenkins: For global configuration, plugin management, and security settings.
• Build History: Shows the status of recent job runs.
• Build Executor Status: Displays the current activity of your Jenkins server.

In Jenkins, an 'Item' or 'Job' (also called a 'Project') is the core unit of work. It's a configured task that Jenkins will execute, like building a software project, running tests, or deploying an application.

The two most common job types are:

• Freestyle Project: A highly flexible, GUI-driven job type for simple to moderately complex tasks.
• Pipeline: Defined by a Jenkinsfile (code-based), ideal for complex, multi-stage CI/CD workflows.

Let's create a simple Freestyle project to see Jenkins in action:

1. Click 'New Item' on the dashboard.
2. Enter a name (e.g., MyFirstJob), select 'Freestyle project', and click 'OK'.
3. In the configuration page, under the 'Build Steps' section, click 'Add build step' and choose 'Execute shell'.
4. Enter a simple shell command and click 'Save'.

Then, click 'Build Now' on the job's page to run it!

Jenkins is a crucial tool in modern software development. Let's see if you've grasped its main purpose.

Great job! You've successfully been introduced to Jenkins, understood its importance, set it up using Docker, navigated its interface, and even created your first automated job.

You now have a foundational understanding of Jenkins. Next, you'll learn how to integrate Jenkins with Docker to build and push images, and automate deployments, truly unlocking its CI/CD potential!