50 Essential Kubernetes Interview Questions for Beginners to Advanced Users

Kubernetes Interview Questions:

Basic Level:

1. What is Kubernetes, and what are its primary components?
   • Kubernetes is an open-source container orchestration platform that automates the deployment, scaling, and management of containerized applications. Its primary components include the API server, etcd, controller manager, scheduler, and kubelet.
2. What are Pods in Kubernetes?
   • A Pod is the smallest deployable unit in Kubernetes, representing a single instance of a running process in a cluster. It can contain one or more containers that share the same network namespace.
3. What is the purpose of a Kubernetes Node?
   • A Node is a worker machine in Kubernetes that runs Pods. It can be a physical or virtual machine and contains the necessary components to run containerized applications.
4. What is a ReplicaSet?
   • A ReplicaSet ensures that a specified number of Pod replicas are running at any given time, providing high availability and scaling for applications.
5. What is a Deployment in Kubernetes?
   • A Deployment is a higher-level abstraction that manages ReplicaSets and provides declarative updates to Pods, allowing for easy rollouts and rollbacks.
6. What are Services in Kubernetes?
   • A Service is an abstraction that defines a logical set of Pods and a policy to access them, enabling load balancing and stable networking.
7. What is the difference between a ClusterIP, NodePort, and LoadBalancer Service?
   • ClusterIP provides internal access to Pods within the cluster, NodePort exposes the service on a specific port on each Node, and LoadBalancer provisions a load balancer for external access.
8. How does Kubernetes handle scaling?
   • Kubernetes supports horizontal scaling by allowing users to adjust the number of replicas in a Deployment or use the Horizontal Pod Autoscaler to automatically scale based on resource utilization.
9. What is the role of the kubelet?
   • The kubelet is an agent that runs on each Node in the cluster, responsible for managing Pods and ensuring that the desired state matches the actual state by monitoring the health of containers.
10. What is a namespace in Kubernetes?
    • A namespace is a virtual cluster within a Kubernetes cluster, providing a way to segment resources and manage access control for different environments or teams.

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Intermediate Level:

11. What are ConfigMaps and Secrets in Kubernetes?
    • ConfigMaps store non-sensitive configuration data in key-value pairs, while Secrets store sensitive information, such as passwords or API keys, with additional security features.
12. How do you perform rolling updates in Kubernetes?
    • Rolling updates can be performed by updating the Deployment configuration, allowing Kubernetes to gradually replace old Pods with new ones without downtime.
13. What is the purpose of Persistent Volumes (PV) and Persistent Volume Claims (PVC)?
    • PVs are storage resources in the cluster, while PVCs are requests for storage by Pods. Together, they enable dynamic provisioning and management of persistent storage.
14. What is the role of the Kubernetes API server?
    • The API server is the central component of the Kubernetes control plane that exposes the Kubernetes API, facilitating communication between components and clients.
15. What is Helm, and how does it relate to Kubernetes?
    • Helm is a package manager for Kubernetes that simplifies the deployment and management of applications by using charts, which are pre-configured Kubernetes resources.
16. How do you monitor Kubernetes clusters?
    • Monitoring can be achieved using tools like Prometheus for metrics collection, Grafana for visualization, and tools like ELK Stack for log management.
17. What is a StatefulSet, and when would you use it?
    • A StatefulSet is a Kubernetes resource designed for managing stateful applications, providing stable network identities, and persistent storage for each Pod instance.
18. What is the difference between Kubernetes Jobs and CronJobs?
    • A Job creates one or more Pods to perform a specific task until completion, while a CronJob runs Jobs on a scheduled basis at specified intervals.
19. How does Kubernetes perform health checks on Pods?
    • Kubernetes uses liveness and readiness probes to determine the health of Pods. Liveness probes check if a Pod is running, while readiness probes determine if it can receive traffic.
20. What is the purpose of a Ingress resource?
    • An Ingress resource manages external access to services within a cluster, providing features like load balancing, SSL termination, and URL routing.

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Advanced Level:

21. What is the Kubernetes control plane?
    • The control plane is the set of components that manage the Kubernetes cluster, including the API server, etcd, controller manager, and scheduler, overseeing the cluster’s desired state.
22. What are taints and tolerations in Kubernetes?
    • Taints are applied to Nodes to prevent Pods from being scheduled on them, while tolerations are applied to Pods to allow them to be scheduled on Nodes with matching taints.
23. How do you manage resource quotas in Kubernetes?
    • Resource quotas are set at the namespace level to limit the amount of resources (CPU, memory, etc.) that can be consumed by Pods within that namespace.
24. What is the purpose of the Kubernetes scheduler?
    • The scheduler is responsible for selecting suitable Nodes for Pods to run on based on resource availability, constraints, and policies.
25. What is the concept of operators in Kubernetes?
    • Operators are a method of packaging, deploying, and managing Kubernetes applications by extending the Kubernetes API to manage complex stateful applications.
26. What is the Kubernetes NetworkPolicy?
    • NetworkPolicy is a resource that defines rules for controlling traffic between Pods, allowing for the implementation of security policies at the network level.
27. What are the advantages of using Custom Resource Definitions (CRDs)?
    • CRDs allow users to define their own resource types in Kubernetes, enabling extensibility and customization of the Kubernetes API for specific use cases.
28. How do you ensure high availability in a Kubernetes cluster?
    • High availability can be achieved by deploying multiple control plane components, using replication for Pods, and spreading them across different Nodes and availability zones.
29. What is the role of etcd in Kubernetes?
    • etcd is a distributed key-value store that serves as the backing store for all cluster data in Kubernetes, maintaining the state and configuration of the cluster.
30. How do you handle secrets management in Kubernetes?
    • Secrets can be managed using Kubernetes Secrets, which are encrypted at rest and can be accessed by Pods at runtime, ensuring sensitive information is securely stored and managed.

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Additional Questions:

31. What is the significance of Helm charts?
    • Helm charts are packages of pre-configured Kubernetes resources that simplify application deployment and management, enabling easy versioning and sharing of applications.
32. What are the common storage options for Kubernetes?
    • Common storage options include cloud provider storage solutions (like AWS EBS, GCP Persistent Disks), NFS, Ceph, and local storage.
33. How do you perform a canary deployment in Kubernetes?
    • A canary deployment can be performed by creating a new Deployment with a smaller percentage of replicas and gradually increasing the traffic to the new version.
34. What are the differences between Docker Swarm and Kubernetes?
    • Docker Swarm is simpler to set up and use, focusing on basic container orchestration, while Kubernetes provides advanced features for scaling, managing, and automating containerized applications.
35. What is the significance of the kube-proxy component?
    • Kube-proxy manages network communication within the cluster, facilitating service discovery and load balancing for incoming traffic to Pods.
36. How do you rollback a deployment in Kubernetes?
    • Rollback can be performed using the command kubectl rollout undo deployment/<deployment-name> to revert to the previous stable version.
37. What is the use of init containers in Kubernetes?
    • Init containers are special containers that run before the main application containers in a Pod, used to perform initialization tasks like setup or configuration.
38. What is the purpose of a service mesh?
    • A service mesh provides a dedicated infrastructure layer for managing service-to-service communication, enabling features like traffic management, security, and observability.
39. How do you handle application configuration in Kubernetes?
    • Application configuration can be handled using ConfigMaps to manage non-sensitive data and Secrets for sensitive information, both of which can be mounted as environment variables or volumes.
40. What are sidecars, and how are they used in Kubernetes?
    • Sidecars are auxiliary containers that run alongside the main application container in a Pod, used for functionalities like logging, monitoring, or proxying requests.
41. What is Kubernetes API Aggregation Layer?
    • The API Aggregation Layer extends the Kubernetes API by allowing custom APIs to be served alongside the main API, enabling more complex resource management.
42. How do you troubleshoot Pods in Kubernetes?
    • Troubleshooting can involve checking Pod logs with kubectl logs, describing Pods with kubectl describe pod, and using kubectl exec to run commands inside the Pod.
43. What is the importance of Helm Repositories?
    • Helm repositories store Helm charts, making it easy to share and distribute applications in a structured manner, similar to package repositories in traditional package managers.
44. What are the differences between ephemeral and persistent storage in Kubernetes?
    • Ephemeral storage is temporary and is lost when a Pod is terminated, while persistent storage is designed to outlive Pods and retain data even after restarts.
45. What are Kubernetes admission controllers?
    • Admission controllers are plugins that govern and enforce how the Kubernetes API server handles requests, allowing for validation and mutation of incoming API requests.
46. What is a Pod disruption budget (PDB)?
    • A Pod disruption budget is a policy that defines the minimum number of Pods that must be running during voluntary disruptions (like maintenance) to ensure application availability.
47. How do you enable and configure horizontal pod autoscaling?
    • Horizontal pod autoscaling can be enabled by deploying a HorizontalPodAutoscaler resource that specifies the target metrics (like CPU or memory utilization) to trigger scaling.
48. What are the differences between containers and virtual machines?
    • Containers share the host OS kernel, are lightweight, and start quickly, while virtual machines run a complete OS and are more resource-intensive, requiring hypervisors.
49. How do you manage access control in Kubernetes?
    • Access control can be managed using Role-Based Access Control (RBAC) to define permissions and roles for users and service accounts within the cluster.
50. What is the Kubernetes dashboard, and how is it used?
    • The Kubernetes dashboard is a web-based user interface that allows users to manage and monitor Kubernetes clusters, view resource utilization, and perform operations like creating and managing applications.