Most frequently asked Jenkins interview Questions

Jenkins interview Questions

 list of the most frequently asked interview questions:

Q1. What is a Jenkins?

Jenkins is open source automation tool written in the Java with plugins built for Continuous Integration-purpose. Jenkins used to build and test  software projects.continuously making  easier for developers to integrate changes to project, and making it easier for the users to obtain a fresh build. It also allows  to continuously deliver your software by integrating with  large number of testing and deployment of technologies.

● First,  developer commits the code to  source code repository. Meanwhile,
Jenkins server checks  repository at regular time intervals for changes.
● Soon after commit occurs, the Jenkins server detects changes that have
occurred in  source code repository. Jenkins will pull those changes ,will
start preparing a new build.
● If the build fails, then  concerned team will be notified.
● If built  successful, then Jenkins deploys  built in the test server.
● After testing, Jenkins generates a feedback  then notifies  developers about
build and the test results.
● It will continue to check  source code repository for the changes made in t
source code and then whole process keeps on repeating.

Q2. Discuss benefits of using Jenkins?

● At the  integration stage, build failures are cached.
● For eachand every  change in the source code an automatic build report notification is
● To notify  the developer about build report success or failure, it is integrated with the LDAPmail server.
● Achieves continuous integration with agile development and test driven development.
● With the simple steps, maven release project is automated regularly.
● Easy tracking of the bugs at early stage in development environment than production.

Q3. What are  pre-requisites for using the Jenkins

● source code repository  is accessible, for instance,  Git repository.
● working build script, like  Maven script, checked into the repository.

Q4. List some of the useful plugins in Jenkins?

Below are some of important Plugins:
● Maven 2 project
● Amazon EC2 , HTML publisher
● Copy artifact
● Join
● Green Balls

Q5.  what are the commands  used to start Jenkins

To start Jenkins  open Console or Command line, then go to  Jenkins
installation-directory. Over there you can use  below commands:

1. start Jenkins: jenkins.exe start
2. stop Jenkins: jenkins.exe stop
3. restart Jenkins: jenkins.exe restart

Q6. Explain how  to set up Jenkins job?

First mention how to create Jenkins job.
1.Go to Jenkins top page and select “New Job”, next  choose “Build free-style softwareproject”.
Elements of this freestyle job:
● Optional SCM, such as CVS / Subversion where your source code resides.
● Optional triggers the control when Jenkins will performs build.
● Some sort of the build script that performs the build like ant, maven/shell script, batch and file . where the real work starts.
● Optional steps to collect  the information out of  build, such as archiving the artifacts
and/or recording javadoc and test results.
● There other Optionas  to notify other people/systems with the build result, such as sending
e-mails, IMs, updating issue tracker, etc..

Q7. Explain how to create a backup and copy files in Jenkins?

To create backup  you need to do is periodically back up your JENKINS_HOME directory. This contains all of your build jobs configurations, your slave node
configurations, your build history. To create  back-up of your Jenkins setup, copy this directory. You can also copy  job directory to clone or replicate  job or rename  directory.

Q8. How to secure Jenkins?

● Ensure that global security is on.
● Ensure Jenkins is integrated with the  company’s user directory with
the appropriate plugin.
● Ensure  matrix/Project matrix is enabled to fine tune access.
● Automate process of setting rights or privileges in Jenkins with the custom version of controlled script.
● Limit physical access to the Jenkins data/folders.
● Periodically run the security audits on same.

Q9 Explain how you can we deploy a custom build of core plugin?

Below are steps to deploy custom build of the core plugin:
● Stop the Jenkins.
● Copy  custom HPI to the $Jenkins_Home/plugins.
● Delete e previously expanded plugin directory.
● Make an empty file called as .hpi.pinned.
● Start the Jenkins.

Q10. Explain  relation between Hudson and Jenkins?

Hudson was  the earlier name and version of  current Jenkins. After
some issue, project name changed from Hudson to Jenkins.

Q11. What  do you do when you see  the  broken build for your project ?

Open  the console output for  the broken build and try to see if any file changes  missed. If  unable to find the issue in that way, then  clean and updatelocal workspace to replicate problem and try to solve it.

Q12. Explain how  to  move or copy Jenkins from one server to other server?

There are multiple ways :

● Move the job from one installation of the  Jenkins to the another by simply copying corresponding job directory.
● Make copy of  existing job.
● Rename existing job by renaming  directory. Note that if you change  job
name you will need to change other job that tries to call the renamed job.

Q13. Mention various ways which build can be scheduled in the 

● By following source code management commits
● After the completion of other builds
● Can scheduled to run at specified time slots
● Manual Build up Requests.

Q14.Differentiate between  Ant , Maven and Jenkins?

Ant  and Maven are Build Technologies where as the  Jenkins is  continuous integration tool.

Q15. list  SCM tools  that Jenkins supports?

Below are the Source code management tools supported by the Jenkins:
● AccuRev
● CVS,
● Subversion,
● Git,
● Mercurial,
● Perforce,
● Clearcase

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