http://dnasab.net/project/dnasab-photography-36/ Jenkins Interview Questions and Answers for beginners and experienced professionals: With an emphasis on Jenkins interview questions, we will go over the key elements of using Jenkins in the Software SDLC process in this article. The Jenkins interview questions blog includes an introduction to continuous integration and continuous deployment, as well as the role Jenkins plays as an automation tool in the SDLC process. There will then be some in-depth discussions on Jenkins’ capabilities and how-to, with a focus on the Jenkins interview questions covering the basic , intermediate and advanced levels.

It is now feasible to provide the generated software to the end-users considerably faster than it was with the previous ways thanks to the most recent developments in the area of Continuous Integration and Continuous Deployment for the Software Development Life-Cycle (SDLC) process.

The blogs provides the common asked interview questions on Jenkins when appeared for DevOps development in IT job opening.  Jenkins helps in automatically the build process for developers once the code is check-in to the Source Code Repository. 

The below given are the top 50 Jenkins interview questions including simple, easy and complex level questions as part of DevOps Engineer role. The Jenkins interview questions are provided for both the beginners and experienced level professionals & DevOps Engineer to have better understanding on the Jenkins Interview questions.

Top 50 Jenkins Interview Questions and Answers for DevOps Engineer

1) What is Continuous Integration in DevOps ?

DevOps supports Continuous Integration and Continuous Development (CI /CD) as a process which enables developers to provide the code fix for the raised defects on priority. Once the code changes are merged into the Version Control System, automatic build deployment process gets started. This allows developers to quick check the build errors and make corrections.

Continuous Integration allows to perform the below activities:

• Automated build deployment process
• Allows to executes Junit test cases
• Allows to validate business scenarios by invoking APIs to test the functional test cases
• Allows to generate build and process related reports
• Allows easy integration with other DevOps Tool

2) What is Jenkins and why it is commonly used ?

Jenkins is the open source continuous  integration (CI) tool which tracks the source version control , automate the build process once the code is checked in to the source code repository , monitor the build process, sends notifications and alerts in case of build failures.

Jenkins allows to integrate plug-ins for Junit testing, coding standard violations, Junit Code Coverage , etc. and helps to get the integrated testing done before it is being mad available as the new build for testers and business users.

3) Describe the features of Jenkins ?

The below given are the features of Jenkins

• Jenkins is a open source continuous integration tool
• Jenkins is one of the most commonly used tool for Continuous Integration and Continuous Development (CI /CD)
• Jenkins can be installed on heterogenous environments supporting different operating system
• Jenkins can be easily distributed among different machines
• Jenkins provide extensibility by integrating plug-ins
• Jenkins provides easy configuration setup
• Jenkins provided pipeline support
• Jenkins can be easily upgraded
• Jenkins can be integrated with other DevOps tool
• Jenkins provide easy documentation

4) Provide advantages of using Jenkins ?

Jenkins provide the below given advantages

• Easy to use code integration and build deployment process
• Allows to perform harness test by integrating Junit test cases
• Jenkins is a free open source tool
• Jenkins provides platform independence
• Jenkins provide numerous plug-ins to integrated and support DevOps Development Activities
• Build errors / bugs can be tracked in the early stage of deployment
• Successful builds with same version can be deployed to higher environments with ease
• Build notifications with build status and build errors helps in code fix and improving overall integration process

5) What are the pre-requisites to install Jenkins ?

Jenkins can be installed on Windows, Linux and MacOS. Jenkins can be integrated with Docker by uploading the latest Jenkins Image to run as the “container” . Docker can also be integrated easily with Kubernetes.

Jenkins uses Application Server as Jetty to run as a standalone application within its own process with the built-in Java Servlet Container

The below system requirements need to be checked before installing Jenkins

• Minimum of 256MB of RAM
• Minimum of 1GB Disk space
• Jenkins can be installed using Java 8 and Java 11 only for both 32-bit and 64-bit versions.
• Java 9 , Java 10 and Java 12 are not yet supported
• Jenkins support Open JDK 8 and Open JDK11

6) How maven integration with Jenkins is useful ?

Maven is a build management tool which stores all the build dependencies in pom.xml which helps in building, testing and running the code. Maven support the project testing life cycle and thus when integrated with Jenkins, it becomes useful to test the project code changes during the deployment process to identify the build specific errors

7) Name few integrated plugins with Jenkins ?

The below given are the few plugins that can be integrated with Jenkins

• Pipeline : REST API
• GitHub Branch Source
• Bitbucket Branch Source
• Junit Attachments
• Amazon S3 Publisher
• AWS Code Commit Trigger

8) What is Jenkins Pipeline ?

Jenkins Pipeline is a combination of plugins which support in implementing continuous delivery pipelines into Jenkins

Jenkins supports Continuous Delivery (CD) process by automating the build process by retrieving the latest source version and deploying it to become it available for business users and customers.

Jenkins Pipeline uses the https://www.jenkins.io/doc/book/pipeline/syntax/ to execute as a “code” to make the deployment process simple for even complex scenarios also. Jenkins Pipeline defines the build process in the test file http://marionjensen.com/2010/08/boom-or-bust.html Jenkinsfile and commits the text file in the project source control repository. Jenkinsfile performs the below steps:

• Automates the Pipeline build process for pull requests from all branches
• helps in code review
• Provides audit trail for the Pipeline
• Common repository for the Pipeline even though multiple code commits

9) Describe syntax types supported by Jenkinsfile ?

Jenkinsfile can be written using below given syntax

• Declarative Pipeline Syntax: Provides more syntax features and helps in reading and writing the code in a easy way. The top-level of the Pipeline must be a block with Pipeline { } . The Blocks supports only Sections, Directive, Steps and assignment statements. Does not support Semicolon as statement separators
• Scripted Pipeline Syntax: Scripted Pipelines Syntax is built using Groovy and provides all possible features of Groovy which helps in implementing continuous delivery process . Scripted Pipeline executes the Jenkinsfile in the top-bottom hierarchy model . Scripted Pipeline handles conditions using if-else and captures the exceptions using try-catch blocks.

10) Which commands can be used to start Jenkins manually ?

The below given commands can be sued to restart Jenkins manually

• (<JENKINS_ENVIRONMENT_URL>)/restart: enables the force start even if the build is in progress
• (<JENKINS_ENVIRONMENT_URL>)/safeRestart: enables restart when all running build get completed

11) What are the available build statuses in Jenkins ?

The Jenkins provides the below given build status

• Aborted: When the build is time-out or manually stopped by the user
• Failed: When the build deployment stopped due to fatal error
• Stable: When the build is successful
• Unstable : When the build was successful but it got Junit test failed
• Successful : When build has compiled with No errors

12) Name few SCM Tools supported by Jenkins ?

The below given SCM Tools can be integrated with Jenkins

• Git
• Clearcase
• CVS
• SubVersion
• Mercurial

13) How to start Jenkins using command-line ?

The Jenkins can be started from command line using jenkins.exe

14) What is a job in Jenkins ?

The term job is deprecated in Jenkins and now it is called as Project.

A job or project is a set of task defined for Jenkins to consider during the Continuous Integration deployment process . A task could be source code compilation, Junit Code Coverage, executing Junit Test Cases, deployment to the specific web server, etc.

15) Describe to build a job in Jenkins ?

The below steps can be provided to build a job:

• Click on Jenkins Dashboard -> New Item
• Select Freestyle Project Option
• Provide job details like build triggers, SCM, etc.
• Provide the file location that need to be part of the build job
• Click ‘Add Build Step’ and select the build option
• Click ‘Build Now’ . This saves the build configuration and run the build

16) How to integrate a 3rd party tool in Jenkins?

The below steps can be performed in Jenkins to integrate 3rd Party tool

• Install the Node
• Install the Jenkins plugin code from Jenkins Admin Console
• Navigate to Admin-> Manage -> Configure Settings
• Configure Node to build job in the Jenkins Pipeline

17) Explain user authentication process in Jenkins ?

The below steps can be performed in Jenkins to authenticate users

• Persist the user credentials in the database
• Configure Jenkins to authenticate user using LDAP Server
• Configure Jenkins to authenticate user defined by the server where Jenkins is deployed

18) Difference between Jenkins and Bamboo ?

Jenkins Deployment	Bamboo Deployment
Jenkins is an open source continuous integration tool	Bamboo requires commercial continuous integration tool
Jenkins plugins and development release is supported by Jenkins Community	Bamboo Development Team owns the changes
Due to multiple plugin and SCM Tool integration, Jenkins is less user friendly interface	Bamboo provides user friendly interface
Provides multiple plugins for integration	Bamboo provides more built-in functionality and less plugins

19) Explain Multibranch Pipeline in Jenkins ?

The below given steps can be performed for creating multibranch pipeline in Jenkins

• Click on Jenkins Dashboard -> New Item
• Provide the Project Name
• Select ‘Multibranch Pipeline’ as an option
• Select source code repository location and provide credentials
• Save the Project
• Jenkins creates multibranch Pipeline for repository and pull requests from the branches
• To connect to repository we need URL from repository settings called as HookURL
• Add the HookURL to Webhooks section
• Jenkins can now automatically run the build

20) Difference between Jenkins, Maven and Ant ?

Jenkins	Maven	Ant
Jenkins is a continuous integration tool	Maven is a Build Management Tool	Ant is Java library for building code
Jenkins automate the software deployment process	Maven stores project dependencies in pom.xml for build deployment process	helps in building code deployment using xml
Jenkins provide Plugins for integration	does not provide plugin integration	does not provide plugin integration

21) Give Environment variable names defined in Jenkins?

• $NODE_NAME
• $JOB_NAME
• $WORKSPACE
• $JOB_URL
• $BUILD_URL

22) What is flow control in Jenkins ?

Flow control is mechanism used by Scripted Pipeline structure for executing the Jenkinsfile from top to bottom approach

23) What is Agent Directive in Jenkins?

Agent Directive lets Jenkins know how to and where to execute the pipeline. The agent directive is provided at the top-level of the pipeline block.

24) How can we schedule a build in Jenkins?

The below given options can be sued for scheduling a build in Jenkins

• Schedule a Jenkins build using source code management commits
• Schedule a Jenkins build when all other build get completed
• Schedule a Jenkins build for a specified time as cron job
• Manually raise build request

25) What Does JENKINS_HOME directory contains ?

The JENKINS_HOME directory contains configurations, settings & logs

26) What step to perform when the pipeline first job is successful but second job failed ?

Restart the pipeline from the point where it failed by doing ‘restart from stage’

27) How to automate testing in Jenkins?

Automated tests can be executes using Selenium or maven. The test runs can be scheduled and every time test is executed by Jenkins, it send the report with test results

28) Name other continuous integration tools ?

• Bamboo
• ThoughtWorks
• Perforce
• Integrity

29) What are the types of pipelines in Jenkins?

There are 3 types of pipelines in Jenkins

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

30) What are the steps to deploy a custom build for the core plugin?

The below given steps need to be performed to deploy a custom build for the core plugins:

• Stop Jenkins
• Copy the custom HPI to $Jenkins_Home/plugins
• Delete the previously expanded plugin directory
• Make an empty file called .hpi.pinned
• Restart Jenkins

31) Which type of architecture is recommended for a scalable Jenkins environment ?

A scalable Jenkins infrastructure is advised to use distributed builds since the master maintains coordination while the agents do the bulk of the work. The master and the agent are both highlighted in this manner. The master also offers the GUI and API endpoints.

32) Provide the steps to add a user in Jenkins?

The below steps need to be performed if a new user to be added in Jenkins

• Navigate to Manage Jenkins
• Click on Create User
• Enter all the required user details
• Select Create User

33) How can we change the default port of Jenkins?

Jenkins normally operates on port 8080. We can follow these procedures to switch the current port from 8080 to the desired port number:

Utilize the command line to run Jenkins
Execute the command java -jar -httpPort=desired_port Jenkins.war
If the Windows package is used to install Jenkins, then:

Go to the Jenkins directory under Program Files.
Find -httpPort=8080 in Jenkins.xml and change the port 8080 to the new port number.

34) What is the recommended way of taking backups of Jenkins build jobs ?

Each Jenkins build is stored in the XML configuration. The configuration of each build task controlled by the Jenkins master is backed up when this folder is copied. It’s good if we can do a Jenkins Git integration. When we replicate the folder’s contents, we can see that the build jobs it describes will be reinstated the next time Jenkins is launched.

35) Provide the steps to configure Docker in Jenkins?

The below given steps needs to be performed for configure Dockers in Jenkins

• Navigate to the Jenkins dashboard
• Click on Manage Jenkins on the Jenkins dashboard
• Navigate to the Configuration page
• Select Manage Plugins on the Configuration page
• Click on Available in the tabbed interface. Now all the Jenkins plugins available for installation is shown.
• Search for a Docker plugin in the search box
• Select the Docker plugin

36) Provide the steps to configure Git with Jenkins?

The below given steps needs to be performed for configure Dockers in Jenkins

• Validate if the GitHub Jenkins plugin is installed
• Navigate to Manage Jenkins on the Jenkins dashboard
• Select Configure System
• Choose the GitHub section -> Add GitHub Server
• Add the GitHub token as credentials
• Save the details
• Now, Open the Jenkins project
• Select the checkbox for GitHub project
• Provide the GitHub Repository path for the Project URL
• Navigate to Source Code Management, Select the checkbox for Git box
• Provide the GitHub Repository URL in Repositories
• Navigate to Build Triggers, Select the checkbox for ‘Build when a change is pushed to GitHub’
• Set a webhook to Jenkins after the plugin installation is done
• Navigate to Settings -> Integrations & Services from the GitHub repository
• Select Add Service, and then add Jenkins (GitHub plugin)
• The URL of the Jenkins machine should be given as Jenkins Hook URL. Add /github-webhook/

37) What are the configurations steps required for the Jenkins node agent to communicate with the Jenkins master ?

The methods for launching a Jenkins node agent are as follows:

• Launch a Jenkins node agent from the browser window
• A Jenkins node agent should be launched from the command line.

A JNLP file will be downloaded when a Jenkins node agent is launched. JNLP executes and starts a new process on the client machine.

38) What steps are involved in securing Jenkins?

We must first establish global safety. The user directory must then be integrated into Jenkins using the proper plugin, we must ensure Jenkins’ custom version-controlled script for automating the process of rights and privileges has the project matrix enabled for fine-tuning access. Jenkins data or folders have restricted access. We’ll conduct security reviews on it.

39) Name the two components that Jenkins is most closely connected with.

Jenkin primarily consists of two components.

• Build technologies like Apache Maven 
• Version control systems like GIT and SVN

40) Describe the process for copying or moving Jenkins from one server to another ?

The below given steps need to be performed to copy Jenkins from one server to another 

• Slide a job by copying the relevant job directory from one Jenkins installation to another
• Create a copy of a job directory with a new name to duplicate an already existing job
• Renaming a directory in order to rename an existing job

41) What are the commands that can be used to manually start Jenkins?

The following are two methods you can use to manually launch Jenkins:

(Jenkins_url)/restart: Forces a restart without waiting for builds to complete
(Jenkin_url)/safeRestart: Allows all running builds to complete

42) Name few useful plugins available in Jenkins ?

The below given are the most commonly used plugins in Jenkins 

• Maven 2 project
• Amazon EC2
• HTML publisher
• Copy artifact
• Join
• Green Balls

43) Provide the steps to integrate Kubernetes with Jenkins ?

 Kubernetes is:

• Containerized workloads and services are managed using the portable and open-source Kubernetes platform
• The group of hosts running Linux containers can be quickly and effectively controlled with Kubernetes

The below given steps need to be performed to integrate Kubernetes with Jenkins 

• Deploying Jenkins with Kubernetes Engine is the most effective way to manage a Continuous Delivery (CD) pipeline
• To provide greater fault tolerance, Kubernetes permits the formation of many container instances.
• Jenkins and Kubernetes deploy plug can be used for continuous deployment.

44) What are some of the environmental variables that Jenkins uses by default?

The following are a few Jenkins environmental variables:

$JOB_NAME: The name that you give your job when it is first set up.
$NODE_NAME:  This is the name of the node on which the current build is running.
$WORKSPACE:  Refers to the path of the workspace
$BUILD_URL :    Indicates the URL where the results of the builds can be found.
$JENKINS_URL: This is set to the URL of the Jenkins master that is responsible for running the build