18 Jenkins Interview Questions (With Sample Answers)
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When interviewing for software development positions and other related positions, interviewers may ask you questions about Jenkins. Jenkins is a platform that many developers use to help with continuous integration, and knowledge of it may be useful in many positions. Learning about these interview questions may help you succeed during technical interviews for positions that use Jenkins. In this article, we discuss 18 questions that interviewers may ask regarding Jenkins.
18 Jenkins interview questions with sample answers
Here's a list of common interview questions that relate to Jenkins, with a description of why employers ask them and example answers:
1. What is Jenkins?
Interviewers may ask this question to determine if you have a basic understanding of Jenkins. Some positions may require extensive or basic knowledge of Jenkins, so this question may act as an initial qualifier for such roles. When answering this question, describe the overall definition of Jenkins to the best of your ability.
Example: "Jenkins is a continuous integration platform. It's used by thousands of organizations and developers to automate the process of continuous integration. Automated processes such as automatic builds, code quality analysis, testing and deployment are performed using Jenkins."
2. What are some of the specific tasks that Jenkins can perform?
Interviewers may ask this question as a gentle introduction to the technical aspects of Jenkins. They may also use it to determine if you're familiar with the ways developers typically use Jenkins. Answer this question by listing a few of the core features of the program. You may also want to describe how Jenkins can automate common development tasks, such as integration, regression testing and deployment.
Examples: "Jenkins can be used to build projects automatically, including projects written in Java, C#, PHP and R. Jenkins can also be used for automated testing, which includes unit and functional testing. Finally, it can be used for deployment of project artifacts such as JAR files or WAR files."
3. How does Jenkins relate to other software tools you may have used as a developer?
Interviewers may inquire about the similarities and differences between Jenkins and other popular development tools. This question may also provide an opportunity for you to describe how you might use Jenkins to automate a feature of your own application. Answer this question using examples from your expertise and by relating what Jenkins does with other technologies.
Examples: "Jenkins is similar in some ways to SourceSafe because you can use both for continuous integration. For example, when I was a developer at Archibald Technologies, I used SourceSafe to automate my build process. In the same way, I can use Jenkins to automate my build process."
4. What is a pipeline and how does it relate to continuous integration?
Interviewers may ask this question to gauge your level of knowledge related to pipelines in Jenkins. A pipeline refers to a set of steps that are automatically performed on Jenkins. It uses these steps for the continuous integration process on every build. Some of these steps include code quality analysis, automated unit testing and deployment after you meet acceptance criteria. You can design pipelines in many ways, but they generally follow the same pattern as outlined above.
Example: "A pipeline is a set of tasks that are automatically performed when a project is built in Jenkins. These tasks usually include automated builds, tests and deployments."
5. What does Jenkins use to execute the pipeline?
Interviewers may ask this question to continue to test your knowledge of pipelines in Jenkins. In order for continuous integration to occur, Jenkins needs to know how to perform each step of your build. For example, Jenkins may execute shell commands, install a software package or a script. The tools used by Jenkins for each build are known as executors. There are many executors available, but the most common ones include shell, Maven and Ant.
Examples: "Jenkins uses an Ant executor when it performs builds written in Apache Ant. It also uses a Maven executor when performing builds written in Apache Maven."
6. How does Jenkins run tests?
Interviewers may ask this question to determine if you're familiar with the type of testing available in Jenkins. It's important that you feel comfortable answering this question because interviewers may also ask it during your technical interview as a demonstration of how you might use Jenkins. You may want to briefly describe how to install and configure Jenkins on your machine and mention the currently available test runners within the software.
Examples: "You can use Jenkins for automated testing, which includes unit and functional testing. Jenkins typically performs testing using a combination of unit testing, functional testing, integration testing and smoke-testing."
7. How does Jenkins handle different build types?
Your interviewer may ask this question to determine if you have any knowledge of the differences between platforms. You may explain how different operating systems and applications may affect the ways tests, builds or deployments take place.
Example: "Jenkins can run unit, functional and integration tests across a variety of platforms such as Windows, Linux and Mac OS X. Jenkins can also support continuous deployment on Windows Server 2008, Red Hat Enterprise Linux and Mac OS X."
8. How does Jenkins use configuration files?
Interviewers may ask this question to gauge your level of understanding of the structure of Jenkins. It's important that you feel comfortable answering this question because interviewers may ask it during your technical interview as a demonstration of how you might use Jenkins. You may want to briefly describe the contents of a project in Jenkins and describe how the configuration files are used.
Example: "Jenkins uses various configuration files that include parameters, defaults and environment variables,such as the PATH. You can edit the parameters, defaults and environment variables in the Global Configuration and they tell Jenkins what to do when it runs a build."
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9. How does Jenkins use plugins?
Interviewers may ask this question to determine if you have any knowledge of plugins in Jenkins. You can describe the concept of a plugin in Jenkins and how it can be used to extend its functionality.
Example: "Jenkins uses plugins that are written in Java, PHP and Ruby to add additional functionality such as email notification, custom web server configuration, monitoring service, web caching and file storage."
10. How does Jenkins use encryption to secure data in the pipeline?
Interviewers may ask this question to test your understanding of the method in which Jenkins encrypts sensitive information in the pipeline. You may outline how and when encryption takes place and explain how to configure such a feature.
Example: "Jenkins uses SSL (Secure Sockets Layer) to protect sensitive information while it's being passed across a network."
11. How does Jenkins handle backups?
Interviewers may ask this question to determine if you have any knowledge of the different backup options available. You may outline how to configure backups within Jenkins and describe security concerns related to these options.
Examples: "Jenkins can back up the server data and the JUnit test results. Jenkins stores the backup in a dedicated file for the job. Jenkins doesn't integrate with traditional backups tools so it doesn't include built-in support for backing up server data to an external system."
12. What is a multi-domain deployment?
Interviewers may ask this question to determine if you're familiar with the concept of multi-domain deployment, which is closely related to continuous delivery in Jenkins. You may explain the benefits and how to manage a multi-domain deployment within Jenkins.
Example: "The Jenkins Hosted Pipeline is deployed on a virtual machine and it separates the different components of the pipeline into separate application domains that are isolated from each other."
13. Describe how to set up a remote repository in Jenkins.
Interviewers may ask this question to determine your level of skill related to remote repositories in Jenkins. To answer this question, you can quickly describe the steps to setting up a remote repository in Jenkins, and mention something about centralizing builds and sharing repositories with other developers or teams.
Example: "Jenkins supports a repository pattern, which means that it stores the source code for a project in a central location for all developers. The source code is then built and tested in the same place as it is used. Jenkins also supports multiple commit repositories that allow multiple developers to work on shared resources."
14. How does Jenkins use services?
Interviewers may ask this question to determine how much you know about services and whether they're native to Jenkins or not. You may list out various services available in Jenkins, describe how they perform their functions and mention something about their security features.
Example: "Jenkins supports service plugins that provide additional functionality such as email notification, custom web server configuration, monitoring service, web caching and file storage."
15. How does Jenkins perform version control?
Interviewers may ask this question to determine your level of understanding of version control. You may explain the differences between source control and internal development teams and their use within a project. You can mention features of source control in Jenkins, such as Git, and compare them with similar features in other code management tools.
Example: "Jenkins is used to store source code for an application in a repository and also provides integration with various versioning tools such as Git."
16. What are some common challenges with multi-domain deployment?
Interviewers may ask this question to test your knowledge about challenges related to multi-domain deployment. You may give a quick description of how Jenkins may not support some features in other tools, such as the ability to run on a single domain or having multiple applications that use different resources.
Example: "Jenkins supports multi-domain deployment, and it divides the different parts of the build process into separate application domains that are isolated from each other. Some challenges during this process include the inability to process multiple files in one build, as opposed to passing one full file through a pipeline, not having an option for running jobs in different virtual machines and supporting a single application in multiple domains."
17. What are some hooks?
Interviewers may ask this question to determine your familiarity with the concept of hooking. You may quickly explain the concept and mention some of its benefits that developers would look for while implementing hooks within a codebase. You can mention how they help developers or teams extend Jenkins or customize its behavior. You may describe how they're useful and why you may prefer them over implementing custom logic.
Example: "The Jenkins Hooks API allows developers to add custom functionality to Jenkins by using hooks. You can trigger a hook when certain events occur. For example, if you finish a job, a post-build hook can be used to send out notifications."
18. Describe how you would use Jenkins to test a web application.
Interviewers may ask this question to determine if you have any knowledge about testing web applications in Jenkins. You may list out various techniques that can be used to ensure there's no security breach with public-facing web applications by performing tests in Jenkins.
Example: "Jenkins provides built-in support for web applications that can be used to perform security scanning and test common vulnerabilities. By using a web browser to interact with the application, it's possible to find out if forms are secure and if there are any attack surfaces."
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