Top 20 Jenkins Interview Questions And Answers

Do you have any idea what Jenkins does?

Of course, you do! After all, It is the most useful open-source software that is free! Undoubtedly, all the organization that is rich with DevOps, absolutely love this tool! And why won’t they?  It helps automate the parts of software development related to building, testing, and deploying. So it goes without saying, that it contributes in a huge way towards continuous integration and hence, continuous delivery is just a blink of eyes away! Along with that, It supports version control tools, including AccuRev, CVS, Subversion, Git, Mercurial, Perforce, ClearCase, and RTC, and can execute Apache Ant, Apache Maven as well as arbitrary shell scripts and Windows batch commands. 

So if you are applying for a DevOps position in any organization, not only you should but you must have some basic knowledge of Jenkins to get selected during the interview. So what do the basics of Jenkins cover? Let’s see from these 20 handpicked Jenkins interview questions from the top organizations:

1. What are the software prerequisites that must be met before Jenkins is installed?

The software prerequisites that must be met before Jenkins is installed are:

• Java Development Kit
•  Jakarta Enterprise Edition.
• An embedded Jetty Runtime that can be used if WebSphere or Tomcat is not available.

 

2. How to configure and use third-party tools in Jenkins?

You have to follow these steps to use and configure the third-party tools in Jenkins:

• Install third-party software.
• Make sure that you have a plugin that supports the third-party tool.
• Configure the third-party tool in the admin console.
• Use the plug-in from the Jenkins build job.

3. Name two ways a Jenkins node agent can be configured to communicate back with the Jenkins master.

There are two ways to launch a Jenkins node agent:

• From the browser window
• From the command line

After launching a Jenkins node agent, it will download a JNLP file. The JNLP will help the launch of a new process on the client machine when it runs.

4. How to take a backup of your Jenkins build jobs?

Each Jenkins build is stored within the XML configuration. After copying a folder, the configuration of all the build jobs managed by the Jenkins master can be backed up. While performing a Jenkins Git integration, you can copy the contents of the folder. The build jobs described in the folder will be restored once you start the Jenkins server next time.

5. What are the steps included in a Jenkins pipeline?

So, the steps in a Jenkins pipeline are:

• Build
• Test
• Deploy

6. How to turn off Jenkins Security if the administrative users have locked out of the admin console?

You need to search for a folder that contains a file named config.xml and change the settings to false for the security to be disabled when Jenkins is started the next time.

8. State some of the advantages of using Jenkins.

Some advantages of Jenkins are:

• You will get an automated build report every time you make a change to the source code.
• Continuous integration is achievable with agile methodology principles.
• You can automate the maven release project with the help of a few simple steps.
• You can track bugs easily at an early development stage.

9. What are the requirements for using Jenkins?

A few requirements for using Jenkins are mentioned below:

• A source code repository like a Git repository
• A build script like a Maven script checked into the repository

10. What are some of the useful plugins in Jenkins?

Some of the important plugins that can be used with Jenkins are:

• Git repository
• Amazon EC2
• HTML Publisher
• JDK Parameter Plugin
• Configuration Slicing Plug

11. How to setup a Jenkins job?

Jenkins job can be set up with these following steps:

•   Create a Jenkins job by going to the Jenkins top page 
• Select a ‘New Job’
•  Build a freestyle software project.

Some elements of a freestyle project includes:

• A CVS or a subversion where the source code will reside.
• The optional triggers.
• We need a build script like a Maven or Ant where the script is actually built.

12. What is the process for creating a backup and copy files in Jenkins?

To create a backup for files, you need to keep backing up your Jenkins_Home directory regularly including all the build jobs configuration, slave node configuration, and build history. Else, you can copy a job directory to a clone or can rename the directory.

13. What is the process for securing Jenkins?

The steps of securing Jenkins are:

• You need to ensure global security. 
• Make sure that Jenkins is integrated with the user directory through an appropriate plugin. 
• Enable the project matrix for fine-tuning the access with the help of the custom version-controlled script 
• Run security audits on Jenkins Data and Folder

14. How do you compare the tools, Hudson and Jenkins?

 Hudson was Jenkins’ previous name when it launched. Since there were some issues with the name for which it was changed from Hudson to Jenkins.

15. If there is a broken build in your Jenkins project, then what will you do?

Once you open the console output where the broken build is created, you need to check if there are any file changes that were missed. Once there are no issues in this manner, then you can update your local workspace and replicate the problem and before solving it.

16. From one server to another, how do you copy or move your Jenkins jobs?

You need to follow these steps to copy or move Jenkins jobs from one server to another:

• Copy your jobs directory from the old to the new server. 
• Move the job from the installation by copying the corresponding job directory 
• Make a clone of the job directory by making an existing job’s copy. 
• Rename the job directory later.

17. How to schedule builds in Jenkins?

The steps for scheduling builds in Jenkins are mentioned below:

• Check if you have a source code management commit.
• Complete the other builds.
• Schedule it to run at a specified time.
• Give a manual build request.

18. Name some of the SCM tools that are supported by Jenkins.

Important SCM tools that are supported by Jenkins are:

• Git
• Subversion
• CVS
• Mercurial

 

19. How does Jenkins authenticate users?

There are 3 ways by which Jenkins can authenticate users –

• You can use the default way by storing user data and credentials in an internal database.
• Configure Jenkins in a way that it can use the authentication mechanism defined by the application server on which it is deployed.
• Configure Jenkins to authenticate against the LDAP server.

20. Which commands can be used to start Jenkins manually?

The following commands can be to start Jenkins manually:

1. (Jenkins_url)/restart: To force restart without waiting for build completion.

2. (Jenkin_url)/safeRestart: Waits until all the build gets completed before restarting.

 

Conclusion:

Did any more Jenkins query strike your mind while going through this? Tell us in the comment section below if it did. Or even better, join our DevOps courses to get your all confusions cleared up!

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