CJE: Certified Jenkins Engineer Interview Questions

The CJE: Certified Jenkins Engineer certification proves your worth as a DevOps practitioner, whether you’re managing Jenkins on AWS or in an on-premises data center. And in order to pass the interview and get the job, you’ll need to prove that you have the chops to handle continuous integration and delivery concepts with DevOps best practices as its major features, as well as core CloudBees DevOps best practices. Additionally, you can also go through the CJE: Certified Jenkins Engineer online tutorial to get a grasp of the important resources for exam preparation to enhance your skills and confidence. 

Once you have accepted a job offer and have set an interview date, it’s natural to be nervous. While this is expected, it’s important to remember that the interviewer isn’t out to get you. Chances are, the employer wants you to succeed in their organization and will ask the types of questions listed below to determine if you’re a good fit for the position. So let’s have a look at the list of top CJE: Certified Jenkins Engineer Interview Questions!

Advanced Interview Questions

Can you explain the Jenkins architecture and how it works?

Jenkins is a Java-based open-source automation server that is used for continuous integration and continuous delivery (CI/CD). It is designed to automate the building, testing, and deploying of software.

The Jenkins architecture is comprised of several key components:

1. Master and Node: Jenkins runs on a master server and nodes are the machines that are used to build, test, and deploy code. The master server communicates with the nodes to execute jobs and collect results.
2. Plugins: Jenkins supports a wide range of plugins that extend its functionality. Plugins can add new features or integrate with other tools and services.
3. Job Configuration: Jobs are the tasks that Jenkins performs, such as building a project or testing code. They are configured in the web interface and can be triggered manually or automatically.
4. Builds: A build is the process of compiling and testing code. Jenkins tracks builds and provides a history of builds, including the results and any errors that may have occurred.
5. Build Artifacts: Build artifacts are the output of a build, such as compiled code or test results. They can be stored and retrieved for later use.
6. Jenkins Dashboard: The Jenkins dashboard provides a graphical view of the status of builds, nodes, and jobs. It provides real-time information on the status of builds and can be used to diagnose problems or track progress.

The Jenkins architecture works by receiving code changes from a version control system, such as Git. When code changes are pushed to the repository, Jenkins triggers a build and runs tests to ensure that the code is functional. If the code passes all tests, it is deployed to a production environment. If the code fails a test, the build is marked as failed and the issue is identified and resolved.

Jenkins provides a centralized platform for continuous integration and delivery, making it easy to automate the build, testing, and deployment of software. Its architecture allows for customization and integration with other tools, making it a powerful and flexible automation server.

How do you configure a Jenkins build environment?

I would configure a Jenkins build environment as follows:

1. Install Jenkins: The first step is to install Jenkins on a suitable machine, which can be a local machine or a remote server.
2. Set up Jenkins: Next, set up Jenkins by accessing the web interface and configuring the settings. This includes setting up plugins, users, and authorization.
3. Create a Jenkins Job: Create a Jenkins job by clicking on “New Item” and selecting the type of project you want to build (such as a freestyle project).
4. Configure the Job: In the job configuration page, you can configure various settings such as source control management (SCM), build triggers, build environment variables, and post-build actions.
5. Configure the Build Environment: You can configure the build environment by installing necessary plugins and tools, such as Maven or Gradle, and setting up the necessary environment variables.
6. Add Build Steps: Add build steps by clicking on the “Add Build Step” button and selecting the build action you want to perform (such as compile, test, or deploy).
7. Save and Build: Finally, save the configuration and trigger a build by clicking on “Build Now”. The build will run, and the results can be seen in the “Build History” section of the job.

In conclusion, configuring a Jenkins build environment requires careful planning and execution of various steps, such as installing Jenkins, setting up the environment, and configuring the build environment and job settings.

How do you manage plugins and dependencies in Jenkins?

I manage plugins and dependencies in Jenkins by using the following steps:

1. Installing Plugins: Jenkins plugins can be installed from the Jenkins web interface by using the Manage Plugins section. I ensure to install plugins that are necessary for my build environment and required for my projects.
2. Updating Plugins: Jenkins provides an automatic update mechanism to keep plugins updated. I ensure to regularly update plugins to ensure that the latest security patches are installed.
3. Managing Dependencies: Jenkins provides a built-in Dependency Management mechanism to manage dependencies between plugins and between plugins and the core Jenkins application. I ensure that all dependencies are correctly specified in the dependencies section of the plugin’s POM file.
4. Removing Unused Plugins: I regularly clean up unused plugins to avoid security vulnerabilities and to improve the performance of my Jenkins environment.
5. Version Control System: I use a version control system to manage and version my plugins and dependencies. This allows me to keep track of changes and rollback to a previous version if necessary.

By following these steps, I ensure that my plugins and dependencies are well-managed and secure, and my Jenkins environment runs smoothly.

Can you explain the difference between freestyle and pipeline projects in Jenkins?

Freestyle projects in Jenkins are the traditional way of setting up builds in Jenkins. They are typically used for simple build processes that do not require complex automation. In a freestyle project, the build steps and the build process are defined using a web interface and the build process is executed on a single node.

Pipeline projects, on the other hand, use a pipeline-as-code approach in Jenkins. Instead of defining the build steps through the web interface, the build process is defined in a script file called a Jenkinsfile. The Jenkinsfile is written in Groovy, a scripting language that is optimized for automation. The pipeline script can be stored in a version control system, making it easier to manage and share the build process across teams.

Pipeline projects are more flexible and offer more features compared to freestyle projects. They allow developers to define multiple stages of a build process, add parallel execution of tasks, and easily manage complex workflows. In addition, pipeline projects are executed on a dedicated node and can be easily scaled to handle high-volume builds.

In conclusion, freestyle projects are simpler and easier to set up, while pipeline projects offer more advanced features and are ideal for complex and highly automated build processes.

How do you ensure security in Jenkins?

As a Certified Jenkins Engineer, I ensure security in Jenkins by implementing the following best practices:

1. Role-based Access Control (RBAC): I set up role-based access control to ensure that users have the appropriate permissions for their role in the organization.
2. Authentication and Authorization: I implement strong authentication and authorization mechanisms such as LDAP, Jenkins User Database, and OAuth to prevent unauthorized access to the Jenkins server.
3. Secure Connections: I ensure that all connections to the Jenkins server are secured with SSL or TLS encryption to protect sensitive data.
4. Regular Updates: I keep Jenkins updated with the latest security patches and updates to fix any vulnerabilities that have been discovered.
5. Network Segregation: I isolate the Jenkins server from the public network and segment it into a private network to prevent unauthorized access.
6. Data Backup: I regularly backup all Jenkins data to a secure location to ensure that data is not lost in the event of a security breach.
7. Audit Logs: I regularly monitor and review audit logs to identify any suspicious activity and respond promptly to any security incidents.

By implementing these best practices, I ensure that Jenkins is secure and protected from potential security threats.

Can you explain the role of Jenkins in continuous integration and delivery?

Jenkins is an open-source automation tool that is widely used for continuous integration and delivery. It is used to automate the build, test, and deployment processes of software projects.

In continuous integration and delivery, Jenkins plays a crucial role in ensuring that changes made to the codebase are integrated and tested continuously. The purpose of continuous integration is to catch errors early in the development cycle. Jenkins integrates with the version control system, such as Git, and checks the code for any changes whenever a new code is pushed to the repository.

Once the code is integrated, Jenkins triggers a build process that compiles the code, runs automated tests, and generates artifacts that can be deployed to various environments. Jenkins also provides feedback on the build status and results, including any errors or warnings that need to be addressed.

In continuous delivery, Jenkins automates the deployment of code changes to various environments, including production, test, and development environments. The deployment process is fully automated, ensuring that the code is deployed consistently and with minimal manual intervention.

In conclusion, Jenkins plays a critical role in ensuring that code changes are integrated and deployed smoothly and consistently in continuous integration and delivery. It enables developers to focus on writing code, while Jenkins takes care of the rest.

How do you configure notifications and email notifications in Jenkins?

As a Certified Jenkins Engineer, I will outline the steps to configure notifications and email notifications in Jenkins.

Notifications Configuration:

1. Navigate to the Jenkins dashboard and click on the Manage Jenkins link.
2. Select the Configure System option from the list.
3. Scroll down to the E-mail Notification section.
4. Fill in the SMTP server details such as SMTP server hostname, port, and username and password if required.
5. Provide the default recipients’ email addresses in the “Admin e-mail address” field.
6. Save the changes by clicking on the Save button.

Email Notifications Configuration:

1. Open a Jenkins job for which you want to configure email notifications.
2. Click on the Configure option in the job dashboard.
3. Scroll down to the Build Triggers section.
4. Check the box for the “E-mail Notification” option.
5. Provide the email addresses of the recipients in the “Recipient List” field.
6. Define the email triggers, such as sending an email after a build is successful or failed.
7. Save the changes by clicking on the Save button.

By following these steps, you can configure notifications and email notifications in Jenkins.

Can you discuss the use of Jenkins and Docker together in a continuous integration pipeline?

Jenkins and Docker can be used together to create a powerful continuous integration pipeline. In this setup, Jenkins acts as the orchestrator while Docker provides a consistent and isolated environment for the build and testing processes. The pipeline can be configured to automatically build, test, and deploy code changes to various stages such as development, staging, and production.

Here’s a high-level overview of how Jenkins and Docker can be used together in a continuous integration pipeline:

1. Code commit: Developers commit their code changes to a version control system such as Git.
2. Build triggers: Jenkins is configured to listen for code changes and triggers a build when a new commit is detected.
3. Build environment: Jenkins creates a Docker container for the build process. This container is a sandboxed environment that ensures the build is isolated from the host system.
4. Build process: Jenkins runs the build process inside the Docker container. This process can include compiling code, running unit tests, and building a Docker image.
5. Test environment: After the build process is complete, Jenkins creates a new Docker container for the testing process. This container is used to run integration tests and functional tests.
6. Deployment environment: If the tests pass, Jenkins creates a new Docker container for the deployment process. This container is used to deploy the code changes to the desired environment.
7. Continuous improvement: Jenkins can be configured to collect data from the build, test, and deployment processes to improve the pipeline over time.

Using Jenkins and Docker together in a continuous integration pipeline provides several benefits, including:

1. Consistency: Docker provides a consistent and isolated environment for the build and testing processes, ensuring that the pipeline is always reliable.
2. Scalability: Jenkins and Docker can be configured to run multiple build and test processes in parallel, making it easy to scale the pipeline as needed.
3. Flexibility: Jenkins and Docker can be used together to support a wide range of build and test processes, including custom scripts, integrations with other tools, and more.

Overall, Jenkins and Docker are a powerful combination for building and deploying software in a continuous integration pipeline.

Can you explain the difference between Jenkins and other CI/CD tools such as TravisCI and CircleCI?

Jenkins is one of the most widely used CI/CD tools, known for its versatility and extensibility. It is an open-source tool that provides a wide range of plugins for integrating with different tools and technologies. Jenkins provides a web-based interface for setting up and managing builds, tests, and deployments.

TravisCI is another popular CI/CD tool that is mainly used for open-source projects. It is a cloud-based tool that provides a simplified setup process and a user-friendly interface. TravisCI integrates with Github and is optimized for testing and deploying code to multiple platforms.

CircleCI is a cloud-based CI/CD tool that provides a fast and reliable build and deployment process. CircleCI integrates with popular tools and technologies, including Github, AWS, and Google Cloud. It also provides a comprehensive API and web interface for managing builds and deployments.

In conclusion, while Jenkins, TravisCI, and CircleCI all serve the same purpose of automating the CI/CD process, they differ in their target audience, ease of use, and integration capabilities. Jenkins is more versatile and extensible, TravisCI is more optimized for open-source projects, and CircleCI is known for its speed and reliability.

Can you discuss the use of Jenkins with cloud services such as Amazon Web Services (AWS) and Microsoft Azure?

As a Certified Jenkins Engineer, I would say that Jenkins can be integrated with cloud services such as Amazon Web Services (AWS) and Microsoft Azure to enhance the deployment process.

Jenkins can be installed on AWS instances using EC2 and configured to run builds and deployments. By integrating Jenkins with AWS, organizations can take advantage of the cloud infrastructure to run their builds and deployments on an on-demand basis, reducing the overhead of maintaining dedicated build machines.

Similarly, Jenkins can be integrated with Microsoft Azure to run builds and deployments in the Azure cloud. This can be achieved by setting up virtual machines in Azure and installing Jenkins on them. The advantage of integrating Jenkins with Azure is that the build and deployment process can be managed from the Azure portal, providing a unified platform for DevOps.

In conclusion, the integration of Jenkins with cloud services such as AWS and Microsoft Azure provides organizations with the ability to run their builds and deployments on an on-demand basis, increasing efficiency and reducing overhead.

Basic Interview Questions

1. What is the CI-CD pipeline in Jenkins?

Using CI/CD pipelines, you can automate and streamline the process of software delivery. A CI/CD pipeline builds code, runs tests, and helps you safely deploy a new version of the software. It reduces manual errors, provides feedback to developers, and allows fast product iterations. 

2. What is the difference between continuous delivery and continuous deployment?

Continuous Delivery is nothing but the automation of steps executed to securely get changes into production. Whereas as far as Continuous Deployment is concerned, it focuses on the actual deployment, unlike Continuous Delivery whose focus is on the release strategy. 

3. Could you name the different stages in the CI/CD pipeline?

• Build – where the application is compiled.
• Test – where code is tested.
• Release – where the application delivery to the repository takes place.
• Deploy – where code is deployed to production.

4. What is the difference between job and pipeline in Jenkins?

The major difference between Jenkins jobs and Pipeline jobs is that Pipeline jobs run on the master node, using a lightweight execution environment that translates the Pipeline job into atomic commands for agent nodes.

5. How would you define Jenkins build artifacts?

Artifacts are files generated by Jenkins. These files are then stored on the Jenkins server so they can be shared with other computers. Jenkins Artefacts can be used to distribute software.

6. Could you name some build triggers in Jenkins?

• Trigger builds remotely.
• Build after other projects are built.
• Build periodically.
• GitHub hook trigger for GITScm polling.
• Poll SCM

7. What is the main point of difference between GitHub and Jenkins?

Jenkins and GitHub Actions allow you to create workflows for your projects. Jenkins lets you define stages within a workflow, while GitHub Actions creates jobs and allows the grouping of jobs or individual commands within those jobs. Both Jenkins and GitHub Actions support building applications with containers.

8. Can you explain how Jenkins builds the source code?

Jenkins allows you to execute a predefined list of steps, like compiling Java source code and building a JAR from the resulting classes. These can be triggered by time or event. For instance, you can compile any Java-based application every 20 minutes or even after a new commit in the related Git repository.

9. Do you know what makes for a good changelog?

Provide only essential, straightforward, and clear information. Avoid putting fluff into your changelog, even if it’s charming. There are some exceptions; however, even the most charming changelogs use few, very carefully selected words to convey a sense of humor.

10. What is meant by the term Infrastructure as code?

Infrastructure as Code (IaC) is a strategy relying on the use of code-based asset management rather than manual processes. Configuration files are created that contain an organization’s infrastructure specifications, which makes it easier to edit and share.

11. What is a master in Jenkins?

The Jenkins master application schedules jobs assign slaves to do the work and sends builds to those slaves so that they can execute jobs. It also tracks slave status (offline or online) and retrieves build result responses from the slaves. These results are then displayed on the console output.

12. Why is software configuration management important?

Configuration management is a must-have when building complex software systems. The lack of configuration management can cause serious problems with reliability, uptime, and the ability to scale a system. Many popular development tools have configuration management functionality built-in.

13. Could you explain the disadvantages of polling the SCM?

This option is good when you want to check for new commits to your repository. The downside is that your commits won’t be built instantly, and all of them will be built at once.

14. What will happen if the build fails in Jenkins?

The Jenkins Build Failure Analyzer plugin uses a knowledge base of build failure causes to determine the likely cause of failed builds. This knowledge base is maintained from scratch.

15. Can Jenkins run the same job parallelly?

Jenkins allows builds to be run in parallel. Check the option on the Configure page to set “Execute concurrent builds if necessary.” Also, set the number of executors on the Master node configuration page to more than 1.

16. Is it possible to have multiple stages in the Jenkins pipeline?

Jenkins Pipeline automates processes for software developers. The Pipeline modeling process allows you to easily create sequences of steps that work together to create a workflow. Steps can be considered commands that perform a single action. When a step is successful, the pipeline moves on to the next step. When a step fails to execute correctly, the pipeline fails.

17. What is Jenkin’s slave image?

Jenkins images are based on a Debian base image and contain a Java Development Kit (JDK) and the Jenkins agent executable. Such images are published as Jenkins/slave. Furthermore, these images are now deprecated and use Jenkins/agent.

18. What is a Jenkins executor?

An executor is a basic building block of build execution inside a Jenkins agent. An executor can be thought of as a single “process ID” that runs on the machine where the agent is installed, or as the basic unit of resource that Jenkins uses to run a build.

19. Could you explain the use of parameterized trigger plugin in Jenkins?

This plugin allows you to trigger new builds when a previous build has been completed, with options for several parameters for the new build. The Subprojects are displayed in the Jenkins UI when you are looking at a project that triggers them.

20. What is the difference between upstream and downstream jobs in Jenkins?

If you run a project that is configured as an upstream job, then another project may be triggered as part of the former project’s execution. If you run a project that is configured as a downstream job, then that project will be triggered as part of a larger project’s execution.

21. What is the use of Jenkins CLI?

Jenkins has a built-in command-line interface allowing all users and administrators access to Jenkins through a script or even a shell environment. This access is a convenient way for routine tasks scripting, bulk updates, troubleshooting, and many more functions.

22. Could you tell the purpose of build promotion?

Build Promotion is the action of moving a build from one maturity level to another. Maturity level refers to the status of a package (development, staging, or release).

23. How would you describe a Jenkins agent?

A Jenkins agent is a computer program used to carry out various builds when requested by a controller. The controller sends commands to the agents, which take care of performing different tasks within the larger framework of the build operation. In a single Jenkins node configuration, the controller can also act as both an agent and run build jobs. 

24. What makes Kubernetes different from Jenkins?

Jenkins is a software testing tool that can be used to ensure the quality of your app. Kubernetes is a system for automating deployment, scaling, and management of containers. It’s an orchestration tool for containerized applications.

25. How does Jenkins automatically deploy code to servers?

• Firstly, go to Manage Jenkins, and then Manage Plugins
• Then, navigate to the Build project and then click on the Configure option
• Finally, in the Deploy war/ear to a container section, you need to enter the required details of the server where the files have to be deployed. At the end,  click on the Save option.

26. Do you know how Jenkins test codes?

 Jenkins, a popular CI orchestration tool, provides plugins for integration with multiple test automation tools and frameworks into the test pipeline. In other words, Jenkins is a popular CI orchestration tool. It also provides several plugins for the integration along with multiple test automation tools and even frameworks into the test pipeline.

27. What do you understand by the term code coverage?

Code coverage is a metric that gives you a good idea of how thoroughly your application’s code has been tested. It can be a valuable tool in particular for finding such areas of the code that are tested by the test suites.

28. What are the best practices for managing CI/CD secrets?

• Firstly, map the threats and secure the connections
• Second , tighten up the access control
• Separate the duties and enforce permissions
• Also, keep the secrets secure
• Then, lock up the code repository
• Furthermore, monitor and clean up
• Last but not least, stay informed and always have a plan.

29. What are the issues that people generally face in Jenkins?

Some of the commons problems faced are: 

• Problem 1: Jenkins has too many plugins.
• Problem 2: Jenkins isn’t designed for Docker age.
• Problem 3: Jenkins doesn’t support the microservices well.
• Problem 4: CI != CD.

30. Could you tell the different ways to install Jenkins tools?

Different platforms (such as Linux, Windows, etc.) and different setup methods are available for Jenkins.

• Firstly, as a jar file that is deployed using Java.
• Second, as a repository in the Linux environment.
• Also, as a war file that is deployed to a Servlet like Apache Tomcat.
• Finally, as a Docker container either locally or on a public or private cloud.

Expert’s Corner

Solving practice tests cannot be underestimated. The more you solve, the more you will get to know the exam environment. This will increase your confidence and reduce the chance of you committing mistakes. Remember, practice makes a man perfect. So boost your confidence with our CJE: Certified Jenkins Engineer Free Practice Tests now!