50 Important Jenkins Interview Questions (2021)

Introduction

Jenkins is an open-source, free server that allows testers and engineers to develop reliable technologies for Continuous Integration or flexible construction applications on systems that use Java for coding. It has over 1600 plugins to support any kind of development task. 

Through various plugins, the Jenkins suite provides several benefits in software design, resulting in smoother validated procedures in the shortest amount of time. If no such plugin exists, one can build it and post it on the community website for more fine-tuning. Curious to know more about Jenkins interview questions and answers? Check out these Jenkins interview questions.

List of Interview Questions

Jenkins interview questions and answers usually begin with simple inquiries about the product’s benefits, installation, and so on. After completing this package, you will have no difficulty in answering Jenkins interview questions. These Jenkins interview questions and answers are for experienced developers, testers, and advanced programmers. Always be succinct and to the point in the responses to Jenkins pipeline interview questions and answers. 

These Jenkins interview questions and answers will boost your core interview skills and help you perform better. Be smarter with these Jenkins pipeline interview questions. 

We have collected the questions in this set of Jenkins pipeline interview questions and answers after conducting extensive research and discussing with top Jenkins experts. 

Let’s take a look at these 50 hand-picked Jenkins interview questions from the most prestigious companies:

1. What is Jenkins, and what are its best features?

Jenkins is a Continuous Integration platform that allows for the creation, testing, and implementation of new code. Continuous Integration (CI) is a mechanism in which developers commit updates to the source code from a common repository, and all improvements are created in real-time. This can happen many times a day. The CI server monitors each commitment in real-time, improving code builds and ensuring quick verification. This relieves the testers of their responsibilities, allowing for faster integration and less time wastage.

Jenkins has many appealing features for developers:

• Installation is easy: It is a platform-independent, Java-based software that can install quickly on Windows, Mac OS, and Unix-like operating systems.
• Configuration is easy: Its web interface is simple to install and customize, and it includes error checks as well as a designed support feature.
• Plugins are available: The update center has hundreds of extensions that integrate with any tool in the CI and CD toolchain.

2. Why should we use Jenkins?

Jenkins is often used to consistently design and validate software applications. It makes it easy for developers to implement updates to the code and for users to get the latest version quickly. Jenkins uses plugins to accomplish Continuous Integration. Plugins essentially allow DevOps stages to be integrated.

3. How does Jenkins achieve Continuous Integration?

Continuous Integration is a programming process that requires developers to commit updates to the source code in a public repository many times a day or at frequent intervals. A repository is created for any commitments made. As a result, any challenges can be spotted by the team early on. Moreover, the Continuous Integration platform performs various other tasks, such as deploying the development application to the test server, informing the relevant teams about the construct and test performance, etc. Jenkins uses plugins to accomplish Continuous Integration. Plugins generally allow DevOps stages to be integrated.

4. Name some Continuous Integration tools, and why is Jenkins better than them?

Buddy, Jenkins, TeamCity, Big Eval, GoCD, Bamboo, GitLab CI, and others are examples of continuous integration tools. 

Before Jenkins	After Jenkins
Once all of the developers had finished their allocated coding assignments, they would all commit the code at the very same time. Build is then reviewed and implemented.	As soon as the developer commits the code, it is designed and tested. Throughout the day, Jenkins will create and validate the code many times.
The development process is slow.	The development process moves quickly, and users now have easier access to new features. Profits are increased.

5. Explain DevOps and how Jenkins is used in it?

Azure DevOps (formerly known as Visual Studio Team Services – VSTS) is a series of tools for creating, evaluating, and distributing software. Developing and installing software has become even more effective with Azure DevOps. It is not only a series of software for automating CI-CD using the Microsoft stack but it can also be conveniently integrated with a variety of other third-party tools.

6. List the system requirements for the installation of Jenkins.

Jenkins requires a few basic requirements to be installed on your Windows system.

Hardware Prerequisites

• Jenkins needs at least 256 MB of RAM on your computer or laptop to run.
• Jenkins can take up at least 1 GB of space on your hard disc.

Software Prerequisites

• Since Jenkins is based on Java, you’ll need the most recent update of either the Java Development Kit (JDK) or the Java Runtime Environment (JRE).

7. Explain the process of installation of Jenkins

The measures below should be taken to install Jenkins effectively:

• Go to https://www.jenkins.io/download/ and choose the platform you want to use. 
• Unzip the downloaded package from your local computer’s download spot. Double-click the jenkins.msi file that has been unzipped. 
• Press next on the Jenkins setup pad.
• Selecting the directory where you want the Jenkins instance to be saved (the default location is C: Program Files (x86)Jenkins).
• Click on the install option.
• When the installation is completed, click on finish.

8. Name the Jenkins suite’s essential plugins?

The Jenkin suite’s essential plugins are Docker, Jira, Slack Notification, Maven, Amazon E2C, jUnit, Pipeline, Mailer, and Greenballs.

9. Explain what Groovy means?

Jenkins uses a domain-specific language (DSL) called “Groovy” inside a Pipeline Project (read plugin), which will describe a new pipeline as just a script. That single script may articulate a flow that would typically take several “standard” Jenkins jobs chained around.

Groovy will work in conjunction with Java, and the two languages’ syntaxes are very close. While writing Groovy, when you forget the grammar, you can write in Java syntax. Groovy may be used as one of the Java platform’s scripting languages. Groovy scripts could be named from inside Java, reducing the amount of time spent on Java development.

10. Explain Jenkins’ working in a simple use-case?

Let’s assume a developer is operating on a code and contributes it to the repository.

• Jenkins server scans for adjustments in the repository detects the code and pulls it to start a build.
• If the build malfunctions, the results are sent to the developer to make changes.
• If it succeeds, the build is deployed to a test server.
• A test report is produced and submitted to the developer when the testing is completed. This method is repeated until the code passes all the checks, after which it is deployed to output.

11. How does one start using Jenkins from the command line?

The Jenkins Web application ARchive (WAR) file can be started from the command line in the following manner:

• Download the latest stable Jenkins WAR file to an appropriate directory on your machine.
• Open up a terminal/command prompt window to the download directory.
• Run the command java -jar Jenkins.War.
• Browse to https://localhost:8080 and wait until the unlock Jenkins page appears.
• Continue with the post-installation setup wizard below.

12. Explain the Jenkins pipeline?

A pipeline is a set of interconnected jobs that are executed one after another in a predetermined order. Jenkins pipelines have several modules that can be used to combine and incorporate continuous deployment pipelines. Code is used to convey the directions to be followed.

Jenkins pipeline (or just “Pipeline”) is a collection of plugins that help you set up and use continuous distribution pipelines in Jenkins. A continuous distribution pipeline is an integrated representation of the product delivery process, from source code to consumers and customers.

13. Name the types of pipelines in Jenkins?

There are 3 types:

• CI-CD pipeline (Continuous Integration Continuous Delivery)
• Scripted pipeline
• Declarative pipeline

14. If using SVN polling or scheduling a building job in Jenkins, what syntax is used?

Cron syntax is used for building a job in Jenkins. Cron syntax is represented by five asterisks, each separated by a space. The syntax is as follows – [minutes] [hours] [day of the month] [month] [day of the week]. For example, if you want to set up a Cron for every Monday at 11.59 pm, it would be 59 11 * * 1.

15. Explain how to build a Jenkins job?

The steps for building a Jenkins job are as follows:

• On the Dashboard, click on “New Item.”
• Select “Freestyle Project” from the drop-down menu.
• Enter job specifics such as SCM, build triggers, advanced options, and so on.
• It’s critical to determine the location of any files that need to be created.
• After you’ve labeled all options, click on ‘Add build stage’ and choose the right option. 
• For example, if you wish to create a file, pick the file name and the build command.
• Click on “Build Now” to save the design and perform a test run.

16. Explain user authentication in Jenkins?

Due to various optimizations, Jenkins pipeline programs have become the tool of choice for business companies looking to incorporate and transform continuous distribution (CD) pipelines through Jenkins. CD pipelines are streamlined expressions of the mechanism for getting applications from version control to consumers and clients. Jenkins allows you to build CD pipelines using either a web UI or a Jenkins file that has been dedicated to source control.

17. How is a third-party tool used in Jenkins?

Let’s pretend we want to use Node, a third-party tool.

• Make sure Node is mounted first.
• Install the Jenkins plugin for Node via the Jenkins admin console.
• In the admin console, go to Manage and customize the settings on the Tools page.
• Any optimized nodeJS tool can be added to create a job in a pipeline.
• Because of differences in configurations, the protocol for various third-party tools can vary significantly.

18. What are the differences between Bamboo and Jenkins?

Jenkins	Bamboo
Open-source tool	Commercial tool
Supported by a huge global community	It has a separate production team
Not very user-friendly	More user-friendly features
There are several plugins available to execute different functions.	The majority of features are pre-installed, and there are also extensions available on the Atlassian marketplace.

19. Explain the process used by Jenkins? 

Jenkins uses plugins to simplify the whole continuous implementation and distribution process. The steps are as follows:

• Multiple source code updates are committed to the Git repository by developers.
• The Jenkins server monitors database updates and performs a build for each check-in.
• The developed program is then deployed to the test server by Jenkins (like Selenium). The test results are returned as a response.
• The framework is installed on the production server after all tests have been completed on the test server.
• Via the different stages, the input is again submitted to the developer (test server, Jenkins server, Git repo).

20. What is the JENKINS_HOME directory used for?

The JENKINS_HOME directory contains all of the settings, logs, and configurations.

21. How does one copy files and create a backup in Jenkins?

• You can back up your JENKINS_HOME directory regularly to make a snapshot.
• All build job configurations, slave node configurations, and build history are stored in this directory.
• Copy this directory to make a backup, or copy a working directory to duplicate some job or rename the directory.

22. What is DSL Jenkins?

Jenkins DSL (Domain Specific Language) is a plugin that allows jobs to be specified programmatically but in a human-readable manner. The UI settings are intuitively converted into code using this plugin. You’ll be able to build a version for the job while still keeping track of the updates. The translated code is written in the Groovy programming language.

23. How does one use Jenkins to create a Multibranch Pipeline?

The steps are as follows:

• Open the Jenkins dashboard and select “new object” from the top left menu to generate a new item.
• Click OK after entering your project name and selecting “Multi-branch pipeline” from the drop-down menu.
• After that, choose the repository’s location, branch source (GitHub/Bitbucket), and branch source credentials.
• Save the project.
• Jenkins builds new Multi-branch Pipelines for servers of branches and pulls requests with Jenkins files automatically.
• The HookURL is used to bind to the GitHub repository. This URL can be found in the repository’s settings.
• This HookURL should be added to the Webhooks section.
• Jenkins will automatically trigger the build until the jobs have been generated.

24. What is meant by Blue Ocean when using Jenkins?

Blue Ocean is a contemporary Jenkins UI that provides a tailored interface with a modern style. Any user can build, diagnose, and simulate Continuous Delivery pipelines using this guide. Since it is viewed visually, there are no engineering qualifications required to build or comprehend the pipelines. Furthermore, since each stage can be quickly navigated, detecting automation problems is easy.

25. What is the process of continuous testing?

The steps are as follows:

• Creating a test automation package from consumer stories/requirements using software
• Create a test environment
• Build a prototype data bed by copying and anonymizing output data
• Monitor APIs using service virtualization
• Do parallel output checking

26. How does one integrate the Jenkins process with Git?

The measures to combine Git with Jenkins are as follows:

• Open the Jenkins dashboard and create a new Jenkins career.
• Pick the work form and enter the project name (in the object name). Click on the OK button.
• Fill in the project details. Go to the tab titled “Source Code Management.” The choice ‘Git’ will appear if the Git plugin is already installed in Jenkins.
• If you don’t see it, reinstall the GitHub addon, GitHub Branch Source plugin, GitHub API plugin, Gitclient plugin, etc.
• Restart Jenkins after downloading the plugins to display the improvements.
• Enter the repository URL to get the code from GitHub. Install Git if you don’t already have it on your computer.

27. Create and explain the workflow in a Continuous Delivery Workflow?

We must first create a branch before we can create a CD workflow. The division is where all of the scriptings, checking, and code updates take place. If the research is over, the division modifications are combined and delivered.

28. What are the differences between Continuous Deployment, Continuous Delivery, and Continuous Integration?

Continuous Integration (CI) is the practice of continuously incorporating modifications into the essential program at all phases of the distribution pipeline after being validated in a prototype environment. Jenkins and Bamboo servers make use of CI.

Continuous Delivery is the manual delivery of code (shipping) to a specific test, integration, or manufacturing area.

Continuous Deployment is the automated release of code into the staging or development process after it has passed the CI stage’s testing.

29. Explain the code for a pipeline in Jenkins and enumerate the pipeline types?

Pipeline-as-a-code is a strategy or collection of features that allows you to keep the CI/CD workflow logic throughout the source code repository despite making extra Jenkins branch configurations. This is specific to projects with a Jenkins file folder in the repo’s root folder (containing a pipeline script). Declarative and syntax pipeline syntax are the two forms of pipeline syntax.

30. What is meant by an Agent Directive in Jenkins?

Jenkins is guided by the agent directive about how and when to conduct the Pipeline or its subsets. Agents are required for all pipelines. The agent creates a workspace for the pipeline, including source control checkout files and other required working files. When an executor is usable, it also triggers Jenkins to run the steps needed for execution.

31. What are the differences between Jenkins, Ant, and Maven?

Jenkins uses the continuous integration method, while Ant and Maven work on constructed software. Jenkins can run unit tests and deploy programs automatically, while Maven and Ant can only execute build operations.

Ant is a formal method, while Maven is a full declarative process with a lifecycle. Ant scripts cannot be reused. Maven modules, on the other hand, can be reused. Ant is an ancient technique that is now in use by legacy applications. Maven is used for the majority of new apps.

32. How does one set up the process for a Jenkins job?

Jenkins manages project builds with the help of jobs. There are a few steps to setting up a job:

• Create a new object and mark it after the work.
• Press OK after selecting the freestyle project.
• Fill out the job description and specify the number of builds to keep and how long they should be kept.
• Set up the archive (Example Git). Enter the URL as well as your login credentials.
• Define your create triggers.
• You will save the work.
• Verify the job by pressing the “Build Now” button.

33. What measures are used to secure Jenkins?

Jenkins can be secured and global protection configured by doing the following:

• Launch Jenkins by deploying Jenkins.war to the server.
• Go to Manage Jenkins from the homepage (via URL).
• Click the “Setup Security” button on this page.
• Check the box labeled “Enable Protection.”
• For security reasons, having your database is a good idea. In the “Security Realm,” choose this option and check the “Allow users to sign up” checkbox.

34. In Jenkins, what is meant by an agent?

The agent determines the pipeline’s execution point for a specific stage or the whole pipeline.

35. Define the Jenkins parameters?

Several input parameters may influence the execution of a construct. If you do have several test suites but just want to run one, for example. You can choose which one to run by setting a parameter. To use parameters in work, you must do so when specifying the parameter. The parameter may be a string, a register, or something else entirely.

36. How does one configure communications between Jenkins master and its node agent?

There are two ways to start a node agent:

Browser: A JNLP (Java Web Start) file is downloaded if the Jenkins node agent is launched from a browser. This file starts a new job-running loop on the client computer.

Command-line: The executable agent.jar file is required to launch the node agent from the command line. When you run this file, it starts a loop on your client who communicates with Jenkins to create jobs.

37. What is meant by a trigger? 

Triggers determine where and how pipelines are operated.

• When Jenkins is combined with a source control system (SCM), such as Git, the repository can be polled whenever a commit is made.
• The Git module should be installed and configured first.
• Then you can create a trigger that tells you when a new build should start.

38. What and when is the backup plugin used? 

This is a handy plugin that saves all of the important settings and parameters for future use. This is particularly helpful in case of a malfunction, as it prevents the settings from being lost.

39. What does one do if one has a broken project build?

There are two ways to fix a faulty construct:

• Open the monitor and verify that all of the files have been taken. If any modifications are missed, make sure they are placed right.
• To debug and correct the error, replicate the problem on your local setup.

40. When working on a pipeline, if the second job fails, after the first job was successful, what should one do?

Using the “restart from level” command, we can restart the pipeline from where it failed.

41. How do you copy and move Jenkins to a new server from an older one?

The JENKINS HOME (/var/lib/Jenkins) directory contains all of the configurations and parameters. The whole home directory should be copied to the new server. The command “sync” can be used to do this.

42. What is meant by Maven, and what benefits accrue when Jenkins and Maven are integrated?

Maven is a platform for managing builds. All of the dependencies required to create, validate, and run the code can be configured using a simple pom.xml. Maven is in charge of a research project’s entire lifecycle. The Maven Webdriver can develop the project and run all tests effectively when it is merged with Jenkins.

43. How are automated tests run on Jenkins?

Tools like Selenium or Maven can be used to run automated experiments. The developers can schedule the test runs. Jenkins shows the test results and gives the developers a note.

44. Explain what is meant by the Git plugin? 

Git is software that allows you to trace improvements in a collection of files. It’s typically used to coordinate work by programmers working on source code together during software development. Pace, data consistency, and support for distributed, non-linear workflows are among its objectives (thousands of parallel branches running on different systems).  

45. What are scripted pipelines, and how do they work?

With the aid of a lightweight agent, a scripted Jenkins pipeline continues to run on the Jenkins ace. It makes use of a limited number of assets to interpret the pipeline into nuclear directions. Both declarative and scripted language structures are distinct from one another and are distinguished in unusual ways.

46. In Jenkins, what is the default port?

Jenkins’ default port is 8080.

47. How do I change the Jenkins running port?

The default port can be changed by using the CLI and running Java -jar Jenkins.war –httpPort=8282.

48. In Linux, how do I adjust the port?

In the default directory, /etc/default/Jenkins, edit the text. And then restart with HTTP PORT=8001 set.

49. Explain Jenkins’ Master-Slave architecture?

Jenkins supports the owner-slave model, in which a master employs a large number of slaves. Jenkins Distributed Builds is another name for it. It allows you to run jobs on a variety of platforms, including Linux, macOS, and Windows. We may also use Jenkins Distributed Builds to perform a similar project on several conditions in parallel, allowing you to achieve the best results quickly using this distributed approach. The rest of the task results are collected and analyzed on the master hub.

50. What is a Jenkins Workspace, and how does it work?

Jenkins has a built-in command-line interface that allows you to access it from the content of the shell. This is useful for automating repetitive errands, mass alerts, and inconvenience research, among other things. The Jenkins CLI client, which is a Java JAR file distributed with Jenkins, is used to use this interface.

Conclusion

With these Jenkins pipeline interview questions and answers and interview questions on Jenkins for testers, you will be able to ace your interview. Though not comprehensive, it lays the groundwork for impressing recruiters with your Jenkins skills. Jenkins is indeed a real-time tool for testing and combining mostly automated builds. It keeps track of a small version of a large Java code piece, culminating in system automation, which saves users and developers time.

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