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Top 20 Jenkins Interview Questions and Answers

Published On: June 7, 2024

Jenkins Interview Questions and Answers

Jenkins can be used for a wide range of on-premises and cloud-based software-based automation applications. Jenkins-versed DevOps engineers are in high demand. The top 20 Jenkins interview questions and answers are provided here for the benefit of all applicants.

Jenkins Interview Questions and Answers for Freshers

1. What is Jenkins?

Jenkins is an open-source, self-contained automation server that may be used to automate a wide range of software development, testing, and delivery or deployment operations. 

2. Describe Jenkins’s features.

Here are a few of Jenkins’s most important characteristics:

  • This automation tool is available as open-source and free.
  • The number of plugins offered by Jenkins is enormous.
  • Across a variety of operating systems, setup and installation are simple.
  • Supports pipelines
  • Quick release intervals
  • Simple updates 

3. What is continuous integration?

A method of developing software whereby modifications are incorporated into the main code as soon as a patch is prepared, guaranteeing that the program is constantly available for building, testing, deploying, and monitoring.

4. What is continuous delivery?

In this software development approach, when all quality checks are successful, continuously integrated (CI) changes will be tested and continually released into a particular environment, usually through a manual release procedure.

5. Describe continuous deployment.

A method of software development where, following the completion of all successful quality checks, continuously integrated (CI) modifications are automatically deployed into the target environment

6. What are the typical applications for Jenkins?

Jenkins can be used for any software-based automation because it is an open-source tool. Among the frequent use cases are:

  • Jobs building software
  • Tasks for CI, regression, smoke, and sanity tests
  • Jobs relating to web scraping and data extraction Code coverage measurement
  • All-purpose automation
  • Jobs involving reverse engineering, key decoding, and many more can benefit from software automation. 

7. What is Jenkins pipeline?

A collection of plugins called a Jenkins Pipeline (or just “Pipeline”) aids in integrating and implementing continuous delivery pipelines within Jenkins.

8. What are the two types of pipeline syntax in Jenkins?

Declarative Pipeline Syntax: It is a more organized method for writing pipeline activities in programming. It offers more understandable, easier-to-understand code with clear statements that define actions, including pipeline, agent, stages, and phases.

Scripted Pipeline Syntax: With scripted pipeline syntax, a more adaptable method built on Groovy code, users may create intricate, dynamic pipelines by utilizing conventional programming elements like loops, if/else conditions, and try/catch blocks.

9. In Jenkins, how can a Git repository be cloned?

Developers must first verify that Jenkins has the Git plugin installed before cloning a Git repository. Next, users must choose Git and provide the repository URL in the job configuration’s Source Code Management page.

10. What does Jenkins’ Groovy mean?

Apache Java platforms use the dynamic, object-oriented programming language Groovy for their scripting needs. The Jenkins pipeline is orchestrated using Groovy, which also makes it possible for teams to contribute to the work in many languages.

Because Groovy’s syntax and Java’s are so similar, using Groovy with the Java interface is easier. The language includes many capabilities, including support for development and Java compatibility. 

11. How is Jenkins installed?

To install Jenkins, take the following actions:

  • Install Java 
  • Install Apache Tomcat Server
  • Download the Jenkins War File
  • Deploy Jenkins war File

12. With what commands may Jenkins be started?

The commands to launch Jenkins are as follows:

  • Launch the command prompt.
  • Once the command prompt appears, navigate to the directory containing Jenkins War.
  • Next, execute the subsequent command: 

D:\>Java -jar Jenkins.war

13. How is a Jenkins job set up?

These are the steps you can take to start a Jenkins job:

  • From the menu, choose New Item.
  • Next, give the job a name and choose a free-form job.
  • To create a new job, click OK.
  • You will therefore be able to configure your job on the following page that loads. 

Jenkins Interview Questions and Answers for Experienced

14. Explain Jenkins Shared Library.

Since a portion of the build and automation processes will be the same for the majority of the jobs, there is a possibility that more and more code will be duplicated in each pipeline job as an organization uses more and more of them. In this case, the same piece of code should be duplicated for every other incoming job. 

The Jenkins project introduced the idea of shared libraries or DRY – Don’t Repeat Yourself – to code to prevent duplications.

Shared libraries are collections of code that can be maintained independently and shared across multiple pipeline jobs. These libraries make pipeline code easier to maintain, more modular, and easier to read. Additionally, it expedites the automation of new occupations.

15. How may Jenkins jobs be programmatically started, stopped, or controlled?

One can utilize the Jenkins Remote Access API for tasks such as –

  • Obtaining from Jenkins data about tasks, views, nodes, builds, etc. for programmatic use.
  • Builds can be started, stopped, or aborted, jobs can be enabled or disabled, jobs can be grouped or removed from views, and more.
  • Along with many other features unique to programming languages, you can create, copy, edit, and remove tasks. 

It contains wrappers for Python, Ruby, and Java, three popular programming languages. CURL can be used to trigger it as follows:

Jobs without restrictions

Just send HTTP POST on JENKINS_URL/job/JOBNAME/build.

Jobs with Parametre

A basic illustration of sending “String Parameters”

curl JENKINS_URL/job/JOB_NAME/buildWithParameters  –user USER:TOKEN –data id=123 –data verbosity=high

16. How can you configure the global tools in Jenkins?

The term “global tools” refers to those that must be controlled from within the Jenkins environment and installed externally. Therefore, it also requires the matching Jenkins plugin. Generally speaking, the steps to utilize a global tool are:

  • To add the global tool to the list of global tools that Jenkins uses, install the tool plugin in the Jenkins instance.
  • Install the utility within the Jenkins instance, or give it out (maybe with an install command to download and install it at runtime).
  • Navigate to Manage Jenkins -> Configure Global Tools and configure the global tool-specific configurations by navigating the tool list.
  • Utilize the global tool that has been placed in your pipeline or operation.

17. How can you programmatically obtain the Console log for a specific Jenkins build?

Using the console command in the Jenkins CLI

java -jar jenkins-cli.jar console JOB [BUILD] [-f] [-n N]

It generates the console output to stdout for a given build, just like if you were to run ‘cat build.log’.

Job: The job’s name

BUILD: The build’s URL or build number. Reverts to the most recent build 

-f: Add console output as it is received if the build is ongoing, such as tail -f 

-n. N: Show the final N lines.

Example

ssh -l <ssh_username> -p <port_no> <Jenkins_URL> console <JOB_NAME>

18. How does in-process script approval operate?

Users can utilize a variety of plugins to run Groovy scripts in Jenkins. These plugins run user-provided scripts in a Groovy Sandbox that restricts which internal APIs may be accessed, shielding Jenkins against the execution of malicious scripts.

The script security plugin is the source of this protection. The “In-process Script Approval” action should show up in “Manage Jenkins” as soon as an unsafe method is used in any of the scripts, giving administrators the ability to decide which hazardous methods—if any—should be permitted in the Jenkins environment.

With this in-process script validation, the entire Jenkins ecosystem is more secure.

19. Can we use standard observability tools to keep an eye on Jenkins?

Yes. Popular monitoring systems, such as Prometheus, DataDog, JavaMelody, and a few more, each offer a Jenkins plugin that, when set up, transmits metrics to the relevant platform for observation using the newest tools and technologies. Alarms and notifications can be set up in the same way to provide prompt attention in the event of an issue.

20. What is the Jenkins User Content service?

Administrators can save files inside the $JENKINS_HOME/userContent folder using Jenkins’ “User Content” method, which allows files to be served from yourhost/jenkins/userContent.

To serve images, stylesheets, and other static resources that you can use from different description fields inside Jenkins, think of this as a miniature HTTP server.

Conclusion

Here we have covered the frequently asked Jenkins interview questions and answers that can be expected during your DevOps interviews. Hone your skills with our Jenkins training in Chennai and soar high in DevOps roles.

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