Top 50+ Jenkins Interview Questions And Answers For 2024

Q1). What is Jenkins in DevOps?

Jenkins is a popular automation tool with source code repositories and plugins written in Java and is responsible for continuous integration and delivery. With the help of Jenkins, software products are tested continuously, and it becomes easy for developers to integrate changes with the existing project whenever needed. So, making a new build with Jenkins is much easier than you may think. It enhances the continuous delivery of the project by integrating the software with plenty of testing tools and deployment methodologies. You can get more information about Jenkins from the Jenkins tutorial.

Q2). What are the possible use cases for Jenkins?

Once you are sure of the definition of Jenkins, let us discuss the use cases mentioned below –

• First, a software developer commits code to the SCR (Source Code Repository). Now, the Jenkins server will regularly check the repository for changes.
• As soon as changes are committed, they are analyzed by the server, and Jenkins will pull those changes and start making new builds instantly.
• In case the build is unsuccessful, the concerned team will be notified. At the same time, if the build is successful, then the build will be deployed to the test server.
• Once the testing is complete, Jenkins will send the feedback, and developers will be notified of the new build or test results.
• This is not a one-time process, but the Jenkins server keeps monitoring the repository regularly, and the same process will be repeated, as discussed above.

Q3). Do you know the programming language that is used to build Jenkins?

Yes, Of Course! This is the Java programming language that is used to build Jenkins.

Q4). What are the features of Jenkins DevOps Tool?

Here, you can check the most popular features of Jenkins at a glance –

• Easy Installation,
• Continuous Integration,
• Continuous Delivery,
• Easy Configuration,
• Plug-in, Distributed, and Extensible

Q5). What do you mean by continuous integration in Jenkins?

Continuous integration is a widespread software engineering practice where isolated changes are tested frequently and reported simultaneously. After this, changes are added to the larger code base. Continuous integration is one of the best DevOps practices, too, where the code is integrated with the repository rapidly, several times a day as well. Further, the integration is validated through automated builds and tests.

Q6). How will you explain the concept of pipeline in Jenkins?

A Jenkins Pipeline is simply a set of plugins that support continuous integration and implementation in Jenkins.

Q7). Define the continuous delivery pipeline in Jenkins.

The continuous delivery pipeline is the automated expression of the process for version control from different users or customers.

Q8). What is Jenkins File, and why is it needed in DevOps?

The Jenkins pipeline details are stored in a file that is named the Jenkins file, and it is further connected to the source code repository in general.

Q9). Give one simple example of Jenkins pipeline code.

Here, we have given a pretty simple example for your reference –

Jenkinsfile (Declarative Pipeline)
   pipeline {
	agent { docker ‘maven: 3.3.3’}
	stages {
	stage (‘build’){
	steps{
	sh ‘mvn—version’
     }
   }
  }
}

Q10). Define the declarative pipeline in Jenkins.

This is a highly simple concept in Jenkins that presents a more simplified syntax on the top of pipeline sub-systems. pipeline block example as given below –

Pipeline {

/*insert Declarative Pipeline here */

}

Q11). What do you mean by "groovy" in Jenkins? 

Apache Groovy is a dynamic object-oriented programming language used as a Java platform scripting language. Groovy manages the Jenkins pipeline and allows multiple teams to participate in different languages for the job. The syntax of Groovy is quite similar to that of Java, making it more compatible with the Java interface. The language has elements such as Java compatibility and development support. 

Q12). How do you set up Jenkins?

You can start a Jenkins setup to build jobs by following these steps:

• Choose New from the menu.
• Next, give the job a name and choose a freestyle job.
• To create a new job, click OK.
• As a result, the following page will allow you to configure your job.

Q13). What commands can be used to start Jenkins?

The following are the commands used to launch Jenkins

• Launch the command prompt.
• Go to the directory containing Jenkins after the command prompt opens.
• Then execute the following command 

Q14). How do you back up and copy files in Jenkins?

Jenkins stores all configuration settings, build scripts, and logs in the home directory. Then, if you wish to make a backup of this Jenkins configuration, simply copy this directory. The job directory can also be duplicated in order to clone or rename it.

Q15). What is the difference between continuous delivery and continuous deployment?

Continuous Delivery refers to developing, testing, and releasing software code modifications. The essential aspect of the CD is that the code is constantly deployable. Continuous Deployment is the last step in the DevOps process. It refers to the automatic transfer of developer changes from the repository to the production phase.

Q16). What are the prerequisites for employing Jenkins? 

To operate Jenkins, you need the following:

• A source code repository that can be accessed, for instance, a Git repository.
• A build script, for example, a Maven script

Q17). What are some continuous integration tools for Jenkins?

Some of the other leading continuous integration tools other than Jenkins are

• TeamCity,
• Travis CI,
• Go CD,
• Bamboo,
• GitLab CI,
• CircleCI,
• Codeship

Q18). How can you deploy a custom build of a core plugin? 

Suppose you wish to deploy a custom build of a core plugin. In that case, you can follow the following measures:

• Stop Jenkins
• Then copy the custom HPI to $Jenkins_Home/plugins
• After that, delete the previously expanded plugin directory
• Next, make an empty file called .hpi.pinned
• Finally, start Jenkins

Q19). What is the process of Jenkins?

• Jenkins reviews modifications in repositories regularly, and developers must ensure their Jenkins code analysis regularly. 
• Once the changes are specified, Jenkins catches them and utilizes them to design a new build.
• After that, Jenkins will transverse through various phases in its regular pipeline. As one set finishes, the method will move to the next step.
• If a stage fails, the Jenkins body will stop there, and the software will email the team utilizing it. When finished successfully, the code executes itself in the correct server so that testing starts.
• After the successful testing step, Jenkins shares the outcomes with the team utilizing it.

Q20). What measures could be taken to move or copy Jenkins from one server to another?

There are multiple ways to move or copy Jenkins from one server to another:

• You may move a job from one Jenkins installation to another by copying the related job directory.
• You may copy a current position by making a clone of the job directory with a unique name.
• You may also rename an existing position by renaming a directory.

Q21). What is the history of Jenkins? How did it come into existence? 

Initially called Hudson, Jenkins came into existence when Oracle handled the ownership to resume the development of the product by renaming it, Jenkins.

Q22). What are the benefits of using Jenkins?

Benefits of Jenkins are –

• Provides excellent collaboration between the development and operations team, creating it a single DevOps team.
• Code errors can be caught as early as possible.
• Code deployment is uncomplicated and occurs in minutes, along with the generation of reports.
• Automation of integration creation, thereby reducing the number of integration problems.

Q23). What are the system requirements to install Jenkins?

The minimum configuration required to download and install Jenkins on Linux-

• 256MB of RAM
• 1 GB of drive space
• Java
• Web browser

Q24).  What are the SCM tools that the Jenkins tool supports?

The SCM tools can be defined as source code management tools. Jenkins supports SVN, Clearcase, CVS, Git, AccuRev, Perforce, RTC, and Mercurial.

Q25).  Is it possible to start Jenkins using the command line?

Yes, using jenkins.exe start, we can start Jenkins.

Q26). How will you define the Jenkins agent?

An agent in Jenkins describes the complete pipeline or a particular stage where execution will occur or where the agent is located. This section is available at the higher level inside the pipeline block, but stage-level usage is generally optional. Refer to Jenkins cheat sheet for more information. 

Q27). How can you define the agent directives in Jenkins?

The objective of agent directives in Jenkins is to check how or where the pipeline can be executed. Most of the time, the agent is needed for all possible Jenkins pipelines

Q28). Which scheme is used to support a variety of use cases in Jenkins?

To support a variety of use cases pipeline in Jenkins, the tool relies solely on parameters. These parameters are usually applied at the higher level of the pipeline block or within multiple stages of directives.

Q29). How will you define the Post in Jenkins?

The post is one more additional step that will run upon the completion of a pipeline block. The post can support plenty of post-conditional blocks and makes execution much easier and more logical in DevOps.

Q30). Where the bulk work can be described in the Jenkins?

When one or more stage directives are defined together, the stage is where bulk work can be described in detail. Make sure that for each stage directive, there is one stage defined properly to manage the discrete parts of the continuous delivery process like deploy, manage, or build, etc.

Q31). How can you define the environment directive in Jenkins?

With the help of environmental directives, we can specify a complete sequence of the key-value pairs that could be defined as the environment variables too for different steps where the environment directive is located within the pipeline.

Q32). Define the triggers in Jenkins.

To re-trigger the Jenkins pipeline in multiple automated ways, triggers are defined in Jenkins. A few pipelines are integrated with sources like GitHub, BitBucket, or other triggers first, then implemented to perform a specific action.

Q33). What do you mean by the input directives in Jenkins?

With the help of input directives, you could prompt the inputs with the help of input steps. The stage is paused after different options have been applied and before you enter to the stage agent to evaluate its condition. When the input is approved, you could continue with the stage ahead. The parameters given as part of the input submission will be available in the environment for the rest of the stage.

Q34). What do you understand by the term Parallel in Jenkins?

In the case of the declarative Pipeline, plenty of nested stages can be defined together and executed in parallel. The parallel stages generally don’t contain any agents or tools because they are irrelevant here.

Q35). What is the meaning of the scripted pipeline in Jenkins?

The scripted pipeline is very similar to the declarative pipeline built on top of the underlying pipeline sub-system. We can say that scripted pipeline is a general-purpose language based on Groovy. A list of features or benefits available in Groovy can also be used along a scripted pipeline. In brief, this highly flexible tool results in multiple continuous delivery pipelines.

Q36). How can you define the Control Flows in Pipeline?

When scripted pipelines are executed in sequential order from top to downwards, they are called control flows in the pipeline.

Q37). Is there any prerequisite for using Jenkins?

You need an accessible source code repository (SCR) and a working build script.

Q38). Mention a few plugins that the developers frequently use.

These are Maven, Git, GitHub, Amazon EC2, Join, HTML publisher, Green Balls, Copy artifacts, etc. I found these plugins that are highly popular mentioned above. But there are plenty of plugins available that can be used at your convenience. A tutorial guide for beginners on what is GIT will help you gain more knowledge about “GIT.” 

Q39). Is there any relationship between Hudson and Jenkins?

This would be interesting, knowing that Hudson is the traditional name for Jenkins.

Q40). What to do if you check any broken build?

If any broken build is found, check the local workspace immediately and try to fix it quickly.

Q41). What is the difference between Maven, Ant, and Jenkins?

Maven

• It is a Build tool
• This tool performs build procedures 

Ant

• Ant is a Build tool
• This tool executes build operations 

Jenkins

• Jenkins is a continuous integration tool
• Jenkins may conduct unit tests and deploy applications

Q42). Why is Jenkins operated with Selenium?

Selenium lets Jenkins run tests whenever there are any software shifts or environmental modifications. When the Selenium test suite is integrated with Jenkins, the testing is automated as part of the build procedure.

Q43). What is the difference between bamboo and Jerkins? 

Bamboo

• Bamboo is a commercial tool
• It has a limited and reliable development team
• As compared with Jerkins, this is more user-friendly
• Many built-in elements and plugins are available in the Atlassian marketplace.

Jerkins

• It is an open-source tool
• It has a vast global community
• It is more deficient and user-friendly
• Many plugins serve different functions

Q44). What is the method of creating a Multibranch pipeline in Jenkins?

To build a multibranch pipeline in Jenkins, follow the following measures:

• Open the Jenkins dashboard and make a new item by clicking on 'the new item.'
• Enter the project title and, from the options, choose 'Multibranch pipeline.'
• Click on the OK option. 
• Then specify the repository location and branch origin (GitHub/Bitbucket), and add the branch source credentials.
• After this step, save the task.
• Now, Jenkins automatically makes new Multibranch Pipelines for the repositories.
• Then, to link to the GitHub repo, we require the HookURL.
• To obtain this URL from the repository settings, count this HookURL to the Webhooks section
• Once the jobs get formed, Jenkins will automatically start the process. 

Q45). How can you merge Jenkins with Kubernetes?

• Kubernetes is a transportable, open-source medium for handling containerized workloads and services. With Kubernetes, the hosts running the Linux containers can be quickly and efficiently managed. Kubernetes tutorial will help you understand the basics in more detail. 
• To organize a Continuous Delivery (CD) pipeline, the most efficient method is to deploy Jenkins with Kubernetes Engine.
• Kubernetes allows the creation of numerous container instances to benefit more fault tolerance.
• Kubernetes deploy plugs are used with Jenkins for Continuous Deployment. 

Q46). How can the parameters be specified in Jenkins?

In Jenkins, a build can handle many input parameters. 

• To specify parameters for the job, select the “This project is parameterized” box.
• The drop-down “Add Parameter” function with the parameter types list. Any number of parameters may be counted in the list.

Q47). What do you understand by DSL Jenkins? 

DSL stands for Domain Specific Language. Jenkins position DSL is a plugin that permits us to specify jobs in the programmatic setup with minimal action. You can define your jobs in Jenkins by utilizing a Groovy language. They created the Jenkins job DSL plugin to form versions of the job and manage the records.

Q48). What syntax does Jenkins use to arrange a building job or SVN polling?

Jenkins uses the cron syntax to arrange a building job or SVN polling. 

Cron syntax is described using 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 wish to set up a cron every Monday at 11.59 pm, it would be 

(59 11 * * 1)

Q49). What do you mean by the blue ocean in Jenkins?

Blue Ocean is a stylish UI for Jenkins that assists Jenkins in personalizing knowledge with modern design. Any user can design, analyze, and visualize Continuous Delivery pipelines through this interface. It doesn’t require specialized skills to build or understand the pipelines; everything is visually delivered. Also, detecting automation issues is effortless, as each step can be easily guided.

Q50). What do you understand by the term agent Directive in Jenkins?

The agent directive tells Jenkins how and where to manage the pipeline or its subsets. All the pipelines need agents. The agent generates a workspace to be assigned that contains checkout files from source control and other extra working files required for the pipeline. It also pushes the steps required for execution by Jenkins when an executor is available.

Q51). What is the benefit of the JENKINS_HOME directory?

All the settings, logs, and configurations are kept in the JENKINS_HOME directory.

Q52). What is cloud computing? What is the role of Jenkins in cloud computing? Elaborate with an example.

As an example, let us consider the AWS cloud service. Cloud computing providers employ the CI/CD methodology to push their work to clients while receiving constant feedback. Jenkins is a tool for automating CI/CD pipelines. For example, multiple Jenkins plugins are available for AWS services, such as Amazon EC2 and ECS.

Q53). What is the function of the Git plugin?

The Git plugin is used when you are utilizing Git as the repository.

Q54). Have you run automated tests on Jenkins? How is it performed?

Yes. Automated tests can be run via tools like Selenium or Maven. Developers can prepare the test runs. Jenkins shows the test results and ships a report to the developers.

Q55). What is the benefit of Ansible in Jenkins? 

Ansible is a fantastic asset for IT automation and can be utilized in a CI/CD procedure to set up the target environment and an application on it. The continuous integration and delivery (CI/CD) method utilizing a Jenkins pipeline is the most practical method to use Ansible for environment provisioning and deployment. 

Refer to the Ansible tutorial for a more straightforward introduction to how to use Ansible. Jenkins is a fantastic tool for automation in CI/CD. Shell scripts are regularly used to provision environments or deploy applications in the pipeline stream. Despite the fact that this could work, keeping up with and reusing the contents over the long haul is bulky.

The motivation behind utilizing Ansible in the pipeline stream is to reuse jobs and playbooks for provisioning, leaving Jenkins as a procedure orchestrator rather than a shell script agent.