Basic Jenkins Interview Questions for Freshers

1. What Is Jenkins Used For?

Jenkins is used for automating software development tasks such as code compilation, testing, code quality checks, artifact creation, and deployment. It streamlines the development process, ensuring reliability and quality by automating repetitive tasks in a DevOps context.

2. How To Trigger a Build In Jenkins Manually?

To manually trigger a build in Jenkins:

1. Access the Jenkins Dashboard.
2. Select the specific Jenkins job.
3. Click “Build Now” to start the manual build.
4. Provide build parameters if necessary.
5. Confirm and monitor the build progress in real time.
6. Review the build results on the job’s dashboard.
7. Access build artifacts if applicable.
8. Trigger additional builds as needed.

3. What Is The Default Path For The Jenkins Password When You Install It?

The default path for the Jenkins password when you install it can vary depending on your operating system and how you installed Jenkins. Here are the general default locations for the Jenkins password:

1. On Windows

If you installed Jenkins as a Windows service, the initial administrative password is typically stored in a file called initialAdminPassword inside the secrets directory within the Jenkins installation directory. The path may look something like this: C:\Program Files (x86)\Jenkins\secrets\initialAdminPassword.

2. On Linux/Unix

If you installed Jenkins using a package manager like apt or yum, the initial password might not be stored directly on the file system. In this case, you can typically find it in the console output when you start Jenkins for the first time. You’ll see a message that includes the initial password.

If you installed Jenkins manually, you might need to check the Jenkins home directory, which is often located at /var/lib/jenkins. Within this directory, you can find the secrets directory and, inside it, the initialAdminPassword file.

3. On MacOS

If you installed Jenkins on MacOS, the initial password is generally located in the same way as on Linux or Unix systems. You can look in the secrets directory within the Jenkins home directory.

Please note that these paths can change depending on your Jenkins installation method and configuration, so it’s a good idea to refer to the documentation or installation instructions specific to your setup if you encounter any issues locating the initial Jenkins password.

4. How To Integrate Git With Jenkins?

To integrate Git with Jenkins:

1. Install the “Git Plugin” in Jenkins through the plugin manager.
2. Configure Git in the global tool configuration, ensuring automatic installation is enabled.
3. Create or configure a Jenkins job, selecting Git as the version control system.
4. Specify the Git repository URL and, if necessary, credentials for authentication.
5. Define the branches to monitor and build.
6. Set up build triggers as needed.
7. Save the job configuration and trigger builds manually or automatically based on your settings.
8. Monitor build progress and results in the Jenkins dashboard.

5. What Does “Poll SCM” Mean In Jenkins?

In Jenkins, “poll SCM” means periodically checking a version control system (e.g., Git) for changes. You can schedule how often Jenkins checks for updates. When changes are detected, Jenkins triggers a build, making it a key feature for continuous integration, scheduled tasks, and automated response to code changes.

6. How To Schedule Jenkins Build Periodically (hourly, daily, weekly)? Explain the Jenkins schedule format.

To schedule Jenkins builds periodically at specific intervals, you can use the built-in scheduling feature. Jenkins uses a cron-like syntax for scheduling, allowing you to specify when and how often your builds should run. Here’s a detailed explanation of the Jenkins schedule format and how to schedule builds:

1. Jenkins Schedule Format

The Jenkins schedule format closely resembles the familiar cron syntax, with a few minor differences. A typical Jenkins schedule consists of five fields, representing minute, hour, day of the month, month, and day of the week, in that order:

Here’s what each field means:

1. Minute (0 – 59): Specifies the minute of the hour when the build should run (e.g., 0 for the top of the hour, 30 for the half-hour).
2. Hour (0 – 23): Specifies the hour of the day when the build should run (e.g., 1 for 1 AM, 13 for 1 PM).
3. Day of the month (1 – 31): Specifies the day of the month when the build should run (e.g., 1 for the 1st day of the month, 15 for the 15th day).
4. Month (1 – 12): Specifies the month when the build should run (e.g., 1 for January, 12 for December).
5. Day of the week (0 – 7): Specifies the day of the week when the build should run (e.g., 0 or 7 for Sunday, 1 for Monday, and so on).

Scheduling Examples:

Now, let’s look at some scheduling examples:

Configuring The Schedule In Jenkins

To schedule a build in Jenkins:

1. Open your Jenkins job’s configuration page.
2. In the “Build Triggers” section, check the “Build periodically” option.
3. In the text box that appears, enter your desired schedule using the cron-like syntax.

For example, to schedule a daily build at midnight (00:00), enter 0 0 * * *. Make sure to include the five fields in the schedule.

• Click “Save” to apply the schedule.

Jenkins will now automatically trigger your builds according to the specified schedule. You can use this scheduling feature to automate tasks, such as nightly builds, daily backups, or any other recurring job that fits your project’s needs.

7. What Is Jenkins Home Directory Path?

The Jenkins home directory is where Jenkins stores its critical data, including job configurations, logs, plugins, and more. The location of this directory varies by operating system but can typically be found at:

• Linux/Unix: /var/lib/jenkins
• Windows: C:\Users<YourUsername>.jenkins
• macOS: /Users/<YourUsername>/.jenkins

You can configure its location during installation or in the Jenkins startup script. Understanding this directory is essential for managing and backing up Jenkins data.

8. How To Integrate Slack With Jenkins?

To integrate Slack with Jenkins for notifications:

1. Set up a Slack Incoming Webhook in your Slack workspace to get a Webhook URL
2. Install the “Slack Notification” plugin in Jenkins.
3. Configure Jenkins global Slack settings by adding the Slack Webhook URL.
4. In your Jenkins job configuration, add a “Slack Notifications” post-build action.
5. Specify the Slack channel, customize message options, and select notification preferences (e.g., success, failure).
6. Save the job configuration.
7. Run a build, and Jenkins will send notifications to the specified Slack channel based on build results.
8. Now, Jenkins is integrated with Slack, providing real-time notifications to keep your team informed about build status and progress.

9. What Is A Jenkins Agent?

A Jenkins agent, also called a Jenkins slave or node, is a separate machine or resource that collaborates with a Jenkins master to execute jobs and build tasks. Agents enable parallel and distributed builds, scaling Jenkins’ capacity.

They register with the master, get assigned jobs, execute them on their own hardware or VMs, and report back results. Agents can run on various platforms, making it possible to test and build in different environments.

10. How To Restart Jenkins?

To restart Jenkins, you can follow these steps:

Method 1.Using the Jenkins Web Interface (if available):

• Open a web browser and navigate to your Jenkins server’s URL.
• Log in to the Jenkins web interface if required.
• In the top-right corner, you may see a “Restart” option. Click on it to initiate the restart process.
• Jenkins will display a confirmation dialog. Confirm that you want to restart Jenkins.

Method 2.Using Command Line (Linux/Unix):

• If you have SSH access to the server where Jenkins is installed, you can use the following commands:
• Open a terminal or SSH into the Jenkins server.
• Run the following command with superuser privileges (e.g., using sudo):

sudo systemctl restart jenkins

This command assumes that Jenkins is managed as a systemd service. If Jenkins is managed differently on your system, you may need to use an alternative command.

Step 3. Using Command Line (Windows):

On Windows, you can restart Jenkins as a service using the following commands:

• Open a Command Prompt or PowerShell window with administrator privileges.
• Stop the Jenkins service:

net stop “Jenkins”

• Start the Jenkins service:

net start “Jenkins”

Ensure that you use double quotes around “Jenkins” if the service name has spaces.

Method 4: Using a Container Or Other Deployment Method:

If Jenkins is running inside a container or managed through a different deployment method, you should refer to the specific instructions for that environment. The procedure for restarting Jenkins may differ based on the setup.

Please choose the method that best suits your Jenkins deployment and the level of access you have to the server or environment where Jenkins is installed.

11. What Is The Default Port Number For Jenkins?

The default port number for Jenkins is 8080. When you access the Jenkins web interface via a web browser, you typically use the URL: http://your_jenkins_server:8080/.

Jenkins is a Java-based open-source automation platform with plugins designed for continuous integration. It is used to continually create and test software projects. If you are even slightly aware of Jenkins, then you must know that continuous integration is one of the most important parts of DevOps and the jobs in this field are high in demand.

If you are preparing for jobs in the DevOps domain, you have arrived at the right place. Through extensive research and consultation from experts, we have compiled a list of the 50 most frequently asked Jenkins interview questions in increasing order of difficulty for Freshers, Intermediate-level, and Experienced candidates.

Let’s begin with some basic Jenkins Interview questions for aspiring DevOps engineers.