Top 10 Jenkins interview questions and answers for 2022

It is one of the most basic Jenkins interview questions of DevOps that you can ask to kick off the interview process. You need to follow the following steps in order to start Jenkins -

• Download - Jenkins Generic Java package (.war)
• Launch the command prompt as administrator and execute java -jar Jenkins.war
• Browse to http://localhost:8080 and copy the generated password
• Follow the instructions for setting up plugins and creating first admin users
• Start running Jenkins as a standalone application

Continuous integration (CI) - It is a development practice that enables developers to regularly integrate code changes into a shared repository, after which automated builds and tests are executed. These incremental code changes to production focus on enhancing the speed of software development and deployment process.

Continuous delivery (CD) - It is a process to build, test, and deliver improvements to the codebase. It allows developers to get changes of all types, including new features, configuration changes, bug fixes, and experiments, that too in production.

Continuous deployment (CD) - It is a software release process that allows developers to deliver software components/functionalities frequently through automated deployments. Basically, any developer change made to the codebase is automatically released to the production stage.

There are several ways of moving or copying Jenkins from one server to another:

• Using the thin backup plugin
• Relocating the Jenkins folder from one server to the other (copying the JENKINS_HOME)
• Using job import plugin if the two servers are in the same network

Take a look at the three security mechanisms that Jenkins uses for authenticating users –

• Jenkins stores the user's data and credentials in an internal database for authentication (default)
• It can also use a Lightweight Directory Access Protocol (LDAP) server to authenticate users.
• Furthermore, it can be configured to implement the authentication mechanism that the deployed application server utilizes.

It is one of the best Jenkins pipeline interview questions to assess the candidate's knowledge. Jenkin pipeline is a collection of plugins that assists in the implementation and integration of continuous delivery pipelines into Jenkins. Take a look at two types of Jenkin pipelines-

• Declarative pipeline - It offers richer syntactical features and makes writing and reading pipeline codes easier.
• Scripted Pipeline – It is a traditional way of writing Jenkin pipeline that provides great control over the script and allows to manipulate the flow of the script extensively, enabling developers to build advanced and complex pipelines as code.

Follow the steps to integrate Git with Jenkins-

• Go to Jenkins dashboard
• Click on "manage Jenkins"
• Then go to "manage Plugins"
• When plugins page opens-
  • Select the Git Plugin
  • Click on "install without restart" or "Download now and install after restart"
  • If Git is already installed, you will see a message "no updates available"
• After installation, go to "Manage Jenkins" and you'll see Git plugin with other plugins installed.

An Agent directive instructs how and when to execute the pipelines or their subsets in the Jenkins environment. These Agents should be distinctly labeled so that they can be identified from each other easily. They create a workspace for the pipeline that includes the required working files so that whenever an executor is available, it triggers Jenkins to execute the necessary steps.

You can use either of the following commands to restart Jenkins manually-

• (jenkins_url)/safeRestart – Enables a restart where all running jobs are allowed to complete. However, new jobs will stay in the queue until the restart is complete.
• (jenkins_url)/restart – Forces a restart without waiting for the builds to finish.

Backup plugin Jenkins can be used to back up critical configuration settings. Follow the following steps to have a backup in place –

• Go to Jenkins dashboard and click on "Manage Jenkins"
• Choose “Manage Plugins”
• Search for "Backup Plugin" and select "Install without restart"
• Restart Jenkins instance once done
• Go back to "Manage Jenkins" and select "Backup Manager"
• Click on “Setup”
• Define the directory for your backup and click "save". Make sure your backup directory resides in a different drive from the drive where your Jenkins instance is set up.

You can easily set up a new built job in Jenkins by following the below steps -

• Log on to your Jenkins dashboard
• Click on "New Items" which is displayed at the top left corner of your dashboard
• Enter the relevant details
  • Enter an item name
  • Select "Freestyle project"
  • Press OK
• Enter project details
• Enter repository URL
• After providing the details, tweak the settings under the "build" section as required
• Click "Apply" and "Save" the project
• Build source code by clicking "Build Now"
• Check the status under "Build History"
• Click on "Build Number" and then "Console Output" to see the status