Introduction

DevOps is one of the most popular technology trends. There is a growing demand for DevOps Engineer job in technology companies.

This book contains popular technical interview questions that an interviewer asks for DevOps Engineer position. The questions cover DevOps, Docker, Cloud Computing and Unix areas.

Each question is accompanied with an answer so that you can prepare for job interview in short time. 

We have compiled this list after attending dozens of technical interviews in top-notch companies like- Airbnb, Netflix, Amazon etc. 

Often, these questions and concepts are used in our dailywork. But these are most helpful when an Interviewer is trying to test your deep knowledge of DevOps. 

Once you go through themin the first pass, mark the questions that you could not answer by yourself. Then, in second pass go through only the difficult questions. 

After going through this book 2-3 times, you will be well prepared to face a technical interview for a DevOps Engineer position.

1. What are the popular DevOps tools utilized by your organization?

• Jenkins: An open-source automation server for continuous integration, deployment, and automated testing.
• GIT: A version control tool for tracking changes in files and software.
• Docker: A popular tool for containerization of services, especially beneficial for cloud-based deployments.
• Nagios: Used for monitoring IT infrastructure.
• Splunk: A powerful tool for log search and monitoring production systems.
• Puppet: Employed for automating DevOps tasks to ensure reusability.

2. What are the key benefits of adopting a DevOps approach?

• Release Velocity: DevOps practices enable increased release velocity, allowing more frequent and confident code deployments to production.
• Development Cycle: DevOps shortens the complete development cycle, from initial design to production deployment.
• Deployment Rollback: DevOps incorporates plans for easy rollback in case of failures or issues in production, ensuring confidence in releasing features without downtime.
• Defect Detection: With a DevOps approach, defects are detected earlier in the development process, improving software quality.
• Recovery from Failure: In case of failures, the DevOps process facilitates quick recovery.
• Collaboration: DevOps fosters collaboration between development and operations professionals.
• Performance-oriented: DevOps encourages a performance-oriented culture, enhancing productivity and innovation within teams.

3. Can you outline the typical DevOps workflow employed in your organization?

• Requirement Writing and Task Tracking: Atlassian Jira is used for writing requirements and tracking tasks.
• Code Version Control: Developers check-in code into the GIT version control system.
• Build Automation: Code checked into GIT is built using Apache Maven, with automation handled by Jenkins.
• Automated Testing: During the build process, automated tests are run to validate the code.
• Artifact Management: Built code is stored in the organization’s Artifactory.
• Deployment: Jenkins deploys the code to production, utilizing Docker images for deployment across multiple hosts.
• Monitoring: Nagios is used to monitor the health of production servers, with Splunk providing alerts for any issues or exceptions.

4. How does your organization apply the DevOps approach with Amazon Web Services (AWS)?

• Infrastructure as Code: AWS resources are treated as code, leveraging services like CloudFormation.
• AWS CloudFormation: Templates are created to describe the desired resources and dependencies, allowing for automated deployment of the application and resources in the AWS cloud.
• AWS OpsWorks: Used for configuration management with Chef framework, enabling automation of server configuration, deployment, and management in AWS and on-premises servers.

5. How can you automatically run a script when a developer commits a change into GIT?

GIT Hooks: GIT provides hooks that can execute custom scripts upon specific events. For this case, a post-commit hook can be written on the client-side to execute a custom script containing the desired message and code to run with each commit.

6. What are the main features of AWS OpsWorks Stacks?

• Server Support: AWS OpsWorks Stacks automates operational tasks on any server, whether in AWS or an organization’s own data center.
• Scalable Automation: Automated scaling support allows new instances in AWS to read configurations from OpsWorks and respond to system events.
• Dashboard: OpsWorks enables the creation of dashboards displaying the status of all stacks in AWS.
• Configuration as Code: OpsWorks follows the “Configuration as Code” principle, allowing the definition and maintenance of configurations that can be replicated across multiple servers and environments.
• Application Support: OpsWorks supports various kinds of applications, making it versatile.

7. How does AWS CloudFormation work in AWS?

• Template Creation: A template is created as a simple text file containing information about a stack, which is a collection of AWS resources to be deployed as a group.
• Resource Deployment: Once the template is submitted to AWS CloudFormation, it deploys all the resources specified in the template, automating the process of building new environments in AWS.

8. What is the significance of Continuous Integration and Continuous Delivery (CI/CD) in DevOps?

• Continuous Integration (CI): Developers merge their work into the main branch several times a day, reducing integration problems and ensuring early feedback on new code additions.
• Continuous Delivery (CD): Software teams aim to deliver software in short cycles, allowing incremental changes to be easily delivered to production. CD involves creating a repeatable deployment process, promoting frequent releases.

9. What are the best practices of Continuous Integration (CI)?

• Build Automation: Create a build environment that triggers builds with a single command, automating the process up to deployment to the production environment.
• Main Code Repository: Maintain a main branch in the code repository to store production-ready code, deployable at any time.
• Self-testing Build: Each build in CI should be self-tested, ensuring high-quality changes.
• Daily Commits to Baseline: Developers commit changes to the baseline every day, preventing a large backlog of code awaiting integration.
• Build on Every Commit to Baseline: Every time a commit is made to the baseline, trigger a build to confirm proper integration.
• Fast Build Process: Keep the build process fast to quickly identify any issues.
• Production-like Environment Testing: Maintain a production-like environment for testing and checking for integration issues.
• Publish Build Results: Publish build results on a common site for easy access and collaboration.
• Deployment Automation: Automate the deployment process, enabling stakeholders to access and test the latest delivery in a test environment.

10. What are the benefits of Continuous Integration (CI)?

• Constant Availability: CI ensures that the current build is continuously available for testing, demonstrations, and release purposes.
• Modular Code: CI encourages developers to write modular code that integrates well with frequent code check-ins.
• Easy Reversion: In the event of a failure or bug, developers can easily revert to a bug-free state of the code.
• Reduced Chaos on Release Day: CI practices minimize chaos on release days by facilitating smooth deployments.
• Early Detection of Integration Issues: CI allows for early detection of integration issues during the development process.
• Automated Testing: CI implementation often leads to automated testing, improving overall software quality.
• Early Feedback: Stakeholders can see and provide early feedback on small changes deployed to pre-production environments.
• Metrics Generation: CI and testing generate useful metrics like code coverage and code complexity, aiding in the improvement of the development process.

11. What are the available security options in Jenkins?

Jenkins provides several options to enhance security and ensure system integrity. Some of the key security features and configurations include:

• I. Security Realm Setup: Configure user authentication by integrating Jenkins with an LDAP server for user authentication.
• II. Authorization Setup: Define user permissions and access control to determine resource-level access. Jenkins offers various options for setting up security authorization, such as using Jenkins’ own User Database, integrating with LDAP servers using the LDAP plugin, or implementing Matrix-based security.

12. What are the advantages of using Chef?

Chef is an automation tool used for infrastructure-as-code, providing numerous benefits. Some of the main advantages of Chef are as follows:

• I. Cloud Deployment: Chef allows automated deployment in cloud environments, facilitating seamless provisioning and management.
• II. Multi-cloud Support: With Chef, you can utilize multiple cloud providers, enabling flexibility and avoiding vendor lock-in.
• III. Hybrid Deployment: Chef supports both cloud-based and datacenter-based infrastructure, allowing for a unified approach to managing diverse environments.
• IV. High Availability: Chef automation enables the creation and maintenance of highly available environments, automatically recovering from hardware failures and ensuring system reliability.

13. Can you explain the architecture of Chef?

Chef is composed of several components that work together to automate infrastructure management. The main components of Chef’s architecture include:

• I. Client: These are nodes or individual users that communicate with the Chef server.
• II. Chef Manage: This is a web console used for interacting with the Chef server, providing a graphical interface for managing configuration.
• III. Load Balancer: All Chef server API requests are routed through the load balancer, typically implemented using Nginx.
• IV. Bookshelf: This component stores cookbooks, which contain the configuration instructions for Chef.
• V. PostgreSQL: Chef server utilizes PostgreSQL as its data repository.
• VI. Chef Server: This is the central hub for configuration data, storing cookbooks, policies, and other relevant information. The Chef server can scale to meet the needs of any enterprise.

14. What is a Recipe in Chef?

In Chef, a Recipe is a fundamental configuration element used to define the desired state of a system. It is written in Ruby language and consists of resources defined using patterns. Key aspects of a Recipe include:

• A Recipe is stored in a Cookbook, which is a collection of related Recipes.
• Recipes can have dependencies on other Recipes, allowing for modular and reusable configurations.
• Recipes can be tagged to group related configurations together.
• Before using a Recipe with the chef-client, it needs to be added to the run-list, which specifies the order of execution.
• Chef ensures that Recipes are executed in the specified run-list order, maintaining the desired system configuration.

15. What are the major benefits of using Ansible?

Ansible is a powerful IT automation tool that offers several advantages for large-scale and complex deployments. Some of the main benefits of Ansible include:

• I. Productivity: Ansible enables rapid delivery and deployment, increasing productivity within an organization.
• II. Automation: Ansible provides extensive automation capabilities, allowing teams to focus on delivering innovative solutions.
• III. Scalability: Ansible can be utilized in both small-scale and large-scale environments, accommodating the needs of organizations of all sizes.
• IV. Simplified DevOps: With Ansible, automation tasks can be written in a human-readable language, simplifying the overall DevOps process.

16. What are the main use cases of Ansible?

Ansible is utilized in various use cases, including:

I. App Deployment: With Ansible, we can reliably and repeatedly deploy applications. II. Configuration Management: Ansible supports the automation of configuration management across multiple environments. III. Continuous Delivery: Ansible enables zero-downtime release updates. IV. Security: Ansible allows the implementation of complex security policies. V. Compliance: Ansible helps verify an organization’s systems against rules and regulations. VI. Provisioning: Ansible facilitates the provision of new systems and resources to other users. VII. Orchestration: Ansible simplifies the orchestration of complex deployments.

17. What is Docker Hub?

Docker Hub is a cloud-based registry that serves the following purposes:

Docker Hub enables the linkage of code repositories, building and storing images, as well as providing links to Docker Cloud for image deployment to hosts. It acts as a centralized repository for container image discovery, distribution, change management, workflow automation, and team collaboration.

18. What is your favorite scripting language for DevOps?

In the context of DevOps, different scripting languages serve different purposes. There is no single language that can handle all scenarios effectively. Some popular scripting languages used in DevOps are:

I. Bash: Bash shell scripting is used for automating tasks on Unix-based systems. II. Python: Python is utilized for complex programming tasks and large modules. It offers a wide variety of standard libraries for convenience. III. Groovy: Groovy is a powerful Java-based scripting language that requires JVM installation. It provides advanced features and flexibility. IV. Perl: Perl is another language commonly used for text parsing, particularly in web applications.

19. What is Multi-factor authentication?

Multi-factor authentication (MFA) refers to a security implementation where a user is authenticated through multiple means before being granted access to a resource or service. It differs from simple user/password-based authentication.

The most popular implementation of MFA is Two-factor authentication (2FA), which commonly combines username/password credentials with an RSA token or a similar second factor for authentication. MFA enhances system security and reduces the likelihood of unauthorized access.

20. What are the main benefits of Nagios?

Nagios, an open-source software for monitoring systems, networks, and infrastructure, offers several benefits, including:

I. Monitoring: DevOps can configure Nagios to monitor IT infrastructure components, system metrics, and network protocols. II. Alerting: Nagios sends alerts when critical components in the infrastructure fail. III. Response: DevOps acknowledges alerts and takes corrective actions. IV. Reporting: Nagios can periodically publish/send reports on outages, events, SLAs, and other relevant information. V. Maintenance: During maintenance windows, alerts can be disabled to avoid unnecessary notifications. VI. Planning: Nagios helps in infrastructure planning and upgrades based on historical data.

21. What is State Stalking in Nagios?

State Stalking is a useful feature in Nagios that aids in issue investigation. By enabling stalking on a host, Nagios meticulously monitors the host’s state and logs any changes in that state. This enables identification of changes that might be causing issues on the host.

22. What are the main features of Nagios?

Some of the primary features of Nagios include:

I. Visibility: Nagios provides a centralized view of the entire IT infrastructure. II. Monitoring: Nagios allows monitoring of mission-critical infrastructure components. III. Proactive Planning: With capacity planning and trending, Nagios facilitates proactive infrastructure planning. IV. Extensibility: Nagios can be extended to integrate with third-party tools through APIs. V. Multi-tenancy: Nagios supports a multi-tenant architecture, enabling isolation and management of different user groups.

23. What is Puppet?

Puppet Enterprise is a DevOps software platform used for automating infrastructure operations. It runs on Unix as well as Windows systems. System configuration can be defined using Puppet’s language or Ruby DSL. Puppet’s language allows the description of system configuration, which can then be distributed to target systems through REST API calls.

24. What is the architecture of Puppet?

Puppet is an open-source software based on a client-server architecture. It operates as a model-driven system, with the client referred to as the Agent and the server as the Master. The architecture consists of the following components:

I. Configuration Language: Puppet provides a language for configuring resources. Each resource is defined with a type, title, and a list of attributes. Puppet code is typically written in manifest files.

II. Resource Abstraction: Puppet supports resource abstraction, enabling the configuration of resources across different platforms. Facter, used by the Puppet agent, provides information about the environment, such as IP, hostname, and OS.

III. Transaction: In Puppet, the Agent sends facts to the Master server, which then sends back the catalog to the Client. The Agent applies any necessary configuration changes to the system, and once all changes are applied, the result is sent back to the Server.

25. What are the main use cases of Puppet Enterprise?

Puppet Enterprise is used for the following scenarios:

I. Node Management: Puppet can manage a large number of nodes efficiently.

II. Code Management: Puppet allows the definition of infrastructure as code, facilitating review, deployment, and testing of environment configurations across different stages.

III. Reporting & Visualization: Puppet provides graphical tools for visualizing and monitoring the status of infrastructure configurations.

IV. Provisioning Automation: Puppet enables the automation of server and resource deployment, ensuring faster completion of infrastructure requirements.

V. Orchestration: For large clusters of nodes, Puppet can orchestrate the deployment process based on desired order, streamlining infrastructure environment setup.

VI. Automation of Configuration: Puppet’s configuration automation reduces manual errors and enhances the reliability of the process.

26. What is the use of Kubernetes?

Kubernetes is used for the automation of large-scale deployments of containerized applications. It is an open-source system based on concepts similar to Google’s deployment processes for millions of containers. Kubernetes can be utilized in cloud environments, on-premise data centers, and hybrid infrastructures. It allows the creation of a cluster of servers that work as a single unit, facilitating the deployment of containerized applications without specifying individual machine names. Applications need to be packaged in a way that they do not depend on specific hosts.

27. What is the architecture of Kubernetes?

The architecture of Kubernetes consists of the following components:

Master: The master node is responsible for managing the cluster and performs functions such as scheduling applications, maintaining the desired state of applications, scaling applications, and applying updates.

Nodes: Nodes run applications within the Kubernetes cluster. They can be virtual machines or computers in the cluster. Each node has a software component called Kubelet, which manages the node and communicates with the master. Nodes use the Kubernetes API to interact with the master. When an application is deployed, the master receives requests to start application containers on nodes.

28. How does Kubernetes provide high availability of applications in a Cluster?

Kubernetes provides high availability of applications in a cluster through a Deployment Controller. This controller monitors the instances created by Kubernetes within the cluster. In the event of a node failure or the machine hosting the node going down, the Deployment Controller replaces the affected node automatically. This self-healing mechanism ensures high availability by maintaining the desired state of the applications running in the cluster.

29. Why is Automated Testing a must requirement for DevOps?

In the DevOps approach, software is released frequently to production. To ensure the quality of software deliverables, automated testing is essential. Manual testing is time-consuming, so automation tests are prepared before delivering the software. This allows for early detection of defects in the development process, providing confidence in the software’s quality.

30. What is Chaos Monkey in DevOps?

Chaos Monkey is a concept popularized by Netflix. It involves intentionally causing service failures or disruptions to test the reliability and recovery mechanisms of a production architecture. By simulating failures, Chaos Monkey verifies whether applications and deployments have a built-in survival strategy. This practice helps ensure that the system can handle unexpected failures and maintains high availability and resilience.