Are you preparing for a Kubernetes interview? To help you out, we have compiled over 35 top questions that cover a range of topics from beginner to advanced levels. These questions will help you prepare for Kubernetes-related interview discussions, spanning foundational to advanced operational aspects of the platform.
Top 35+ Kubernetes interview questions with detailed answers
1. What is Kubernetes, and why is it used?
2. What are the main components of Kubernetes architecture?
3. What are Pods in Kubernetes?
4. How does Kubernetes handle Service Discovery?
5. What is a Kubelet?
6. Explain ConfigMaps and Secrets in Kubernetes.
7. What is the role of the Scheduler in Kubernetes?
8. What is a StatefulSet in Kubernetes?
9. How do Deployments differ from StatefulSets?
10. What are Namespaces, and why are they used?
11. Explain the concept of a ReplicaSet.
12. What are DaemonSets, and when should they be used?
13. How does Kubernetes handle load balancing?
14. What is Helm, and how is it used in Kubernetes?
15. What is a Kubernetes Ingress?
16. Explain the concept of Persistent Volumes (PVs) and Persistent Volume Claims (PVCs).
17. What is the role of etcd in Kubernetes?
18. What are Taints and Tolerations?
19. What is a Kubernetes Service Mesh?
20. How does Kubernetes manage secrets?
21. What are Kubernetes Operators?
22. Explain Kubernetes RBAC.
23. What is Horizontal Pod Autoscaler (HPA)?
24. What is a Kubernetes ClusterIP Service?
25. What is the difference between Docker Swarm and Kubernetes?
26. How does Kubernetes handle updates with Rolling Updates and Blue-Green Deployments?
27. What is a Custom Resource Definition (CRD)?
28. What is Kubernetes Network Policy?
29. How does Kubernetes manage resource quotas?
30. What is the purpose of Liveness and Readiness Probes?
31. Explain Kubernetes Persistent Volume Lifecycle.
32. What are the Kubernetes Init Containers?
33. Describe Kubernetes Jobs and CronJobs.
34. What is an Admission Controller in Kubernetes?
35. Explain Kubernetes Pod Disruption Budgets (PDB).
1. What is Kubernetes, and why is it used?
Answer:
Kubernetes is an open-source container orchestration platform that automates the deployment, scaling, and management of containerized applications. It’s widely used because it allows applications to be deployed and scaled efficiently while providing robust tools for managing container lifecycles.
2. What are the main components of Kubernetes architecture?
Answer: Kubernetes architecture includes:
- Master Node: Controls the cluster and manages API server, scheduler, controller manager, and etcd.
- Worker Nodes: Host the application workload with components like kubelet, kube-proxy, and the container runtime.
- etcd: Stores all cluster data, providing a highly available key-value store.
- API Server: The frontend of Kubernetes for communication between components.
- Scheduler: Distributes work across nodes based on resource requirements.
- Controller Manager: Manages different controllers, like Replication and Node controllers, to ensure cluster state consistency.
3. What are Pods in Kubernetes?
Answer:
A Pod is the smallest deployable unit in Kubernetes, representing a single instance of a running application. Pods can contain one or more containers that share storage and networking, allowing them to communicate and function as a single unit.
4. How does Kubernetes handle Service Discovery?
Answer:
Kubernetes uses services to enable service discovery. Each service has a unique IP address within the cluster and can use DNS or environment variables for other components to discover and connect to it.
5. What is a Kubelet?
Answer:
The Kubelet is an agent that runs on each worker node, responsible for managing and running pods on its node. It ensures that containers in a pod are healthy and reports their status back to the API server.
6. Explain ConfigMaps and Secrets in Kubernetes.
Answer:
ConfigMaps are used to store configuration data for applications, while Secrets store sensitive information like passwords. Both can be injected into containers as environment variables or mounted as files.
7. What is the role of the Scheduler in Kubernetes?
Answer:
The Scheduler assigns unassigned pods to worker nodes based on resource requirements, affinity, and taints/tolerations. It ensures optimal resource utilization and balances workload across the cluster.
8. What is a StatefulSet in Kubernetes?
Answer:
StatefulSets are used for managing stateful applications with stable identities, persistent storage, and ordered deployment and scaling, which is essential for applications requiring consistent network identities or data storage.
9. How do Deployments differ from StatefulSets?
Answer:
Deployments manage stateless applications with identical pods that can be replaced seamlessly, while StatefulSets handle stateful applications, giving each pod a unique identity and persistent storage across reschedules.
10. What are Namespaces, and why are they used?
Answer:
Namespaces are virtual clusters within a Kubernetes cluster used for isolating resources among different teams or projects, managing resource limits, and avoiding naming conflicts.
11. Explain the concept of a ReplicaSet.
Answer:
A ReplicaSet is a Kubernetes resource that ensures a specified number of pod replicas are running at any given time. It replaces failed pods and scales up or down as needed. ReplicaSets form the basis of Deployments, allowing for automated updates and rollbacks.
12. What are DaemonSets, and when should they be used?
Answer:
A DaemonSet ensures that a pod runs on all (or specified) nodes in a cluster. They are commonly used for tasks that need to run on every node, such as log collection, monitoring, or system-level services. When a new node is added, the DaemonSet automatically deploys the specified pod on it.
13. How does Kubernetes handle load balancing?
Answer:
Kubernetes supports load balancing at various levels. Internally, Kubernetes uses Services to distribute traffic across pods in a cluster. Externally, load balancers can be provisioned through the cloud provider to direct traffic to a Kubernetes Service. Ingress resources also help manage HTTP and HTTPS traffic.
14. What is Helm, and how is it used in Kubernetes?
Answer:
Helm is a package manager for Kubernetes that simplifies the deployment and management of applications. Helm uses “charts,” which are pre-configured templates for Kubernetes resources. It helps manage the complexity of deployments by providing version control, templating, and easy rollbacks.
15. What is a Kubernetes Ingress?
Answer:
Ingress is a Kubernetes resource that manages external access to services within a cluster, typically for HTTP and HTTPS traffic. Ingress defines routing rules, SSL termination, and load balancing, allowing services to be accessible through a single IP address with customizable paths.
16. Explain the concept of Persistent Volumes (PVs) and Persistent Volume Claims (PVCs).
Answer:
PVs are storage resources in Kubernetes, independent of any pod, allowing data persistence beyond pod lifetimes. PVCs are requests for storage by users, which get bound to PVs. PVCs enable applications to request storage without knowing the storage details, and Kubernetes handles binding to an appropriate PV.
17. What is the role of etcd in Kubernetes?
Answer:
etcd is a distributed key-value store that acts as Kubernetes’ backend storage. It stores all cluster data, including the configuration, state, and metadata of Kubernetes objects. etcd ensures high availability through consensus algorithms, making it essential for maintaining the cluster’s desired state.
18. What are Taints and Tolerations?
Answer:
Taints and Tolerations control pod placement on nodes. Taints are applied to nodes to restrict certain workloads, while Tolerations allow pods to be scheduled on tainted nodes. This feature is useful for isolating critical workloads or ensuring specific nodes only run certain types of applications.
19. What is a Kubernetes Service Mesh?
Answer:
A service mesh is a dedicated infrastructure layer for handling service-to-service communication in a microservices architecture. Kubernetes service meshes like Istio provide traffic management, security, and observability between services. They use sidecar proxies deployed alongside each service to intercept and control network traffic.
20. How does Kubernetes manage secrets?
Answer:
Kubernetes uses the Secrets object to store sensitive data such as passwords, tokens, or keys. Secrets can be mounted as volumes or passed as environment variables to pods. Kubernetes also provides encrypted storage of secrets at rest and limits access to secrets through RBAC.
21. What are Kubernetes Operators?
Answer:
Operators are extensions of Kubernetes designed to manage complex applications and resources. They use custom controllers and custom resource definitions (CRDs) to automate the management of an application’s lifecycle, including deployment, scaling, and updates, based on the application’s operational knowledge.
22. Explain Kubernetes RBAC.
Answer:
Role-Based Access Control (RBAC) in Kubernetes is used to grant access to resources within the cluster. RBAC defines roles (permissions) and bindings (users/groups with those permissions). Roles can be scoped to specific namespaces or the entire cluster, enabling granular access control.
23. What is Horizontal Pod Autoscaler (HPA)?
Answer:
HPA automatically scales the number of pods in a deployment based on CPU utilization or other custom metrics. HPA allows applications to scale up under high loads and scale down when demand decreases, optimizing resource usage and ensuring application responsiveness.
24. What is a Kubernetes ClusterIP Service?
Answer:
ClusterIP is the default service type in Kubernetes, providing an internal IP within the cluster that allows applications to communicate with each other. It is not accessible from outside the cluster, making it ideal for internal service communication.
25. What is the difference between Docker Swarm and Kubernetes?
Answer:
Docker Swarm is Docker’s native container orchestration tool, simpler to set up but less feature-rich. Kubernetes offers advanced features like automated scaling, rolling updates, and extensive networking configurations. Kubernetes is better suited for large, complex applications with microservices architecture.
26. How does Kubernetes handle updates with Rolling Updates and Blue-Green Deployments?
Answer:
Rolling updates replace pod instances gradually, ensuring minimal downtime. Blue-green deployments create a separate environment for updates, allowing rollback by switching traffic back to the old environment if issues arise. Both strategies help ensure application stability during updates.
27. What is a Custom Resource Definition (CRD)?
Answer:
CRDs allow users to define custom resources that extend Kubernetes’ API. This enables Kubernetes to handle specialized applications or custom functionality by creating new resource types. CRDs are widely used for building Operators, as they allow for application-specific configurations.
28. What is Kubernetes Network Policy?
Answer:
Network Policies in Kubernetes control the communication between pods and services at the network level. Policies define which pods can communicate with each other based on labels and selectors, enhancing security by allowing only authorized traffic.
29. How does Kubernetes manage resource quotas?
Answer:
Resource quotas limit resource consumption within a namespace, ensuring fair distribution and preventing resource exhaustion by any single team or application. Administrators define quotas for CPU, memory, and storage, and Kubernetes enforces them at the pod level.
30. What is the purpose of Liveness and Readiness Probes?
Answer:
Liveness probes check if a pod is functioning correctly; if a liveness probe fails, Kubernetes restarts the pod. Readiness probes determine if a pod is ready to accept traffic, helping avoid service disruptions by routing traffic only to healthy pods.
31. Explain Kubernetes Persistent Volume Lifecycle.
Answer:
Persistent Volumes (PVs) in Kubernetes have a lifecycle that includes four stages: Available (waiting to be bound), Bound (assigned to a PVC), Released (PVC deleted), and Failed (when not reusable). Kubernetes manages PV reclamation policies, such as Retain, Recycle, or Delete, based on configuration.
32. What are the Kubernetes Init Containers?
Answer:
Init containers are specialized containers in a pod that run before the main containers. They perform setup tasks, such as checking dependencies or downloading files. Kubernetes ensures that all init containers complete successfully before starting the main application containers.
33. Describe Kubernetes Jobs and CronJobs.
Answer:
Jobs in Kubernetes manage one-time tasks, ensuring pods run to completion. CronJobs schedule Jobs to run at specified times or intervals. Both are useful for batch processing, periodic tasks, and data cleanup operations.
34. What is an Admission Controller in Kubernetes?
Answer:
Admission Controllers are plugins that intercept API requests to enforce policies. They validate or modify requests before they reach etcd, ensuring compliance with security, resource, or operational policies. Examples include PodSecurityPolicy and ResourceQuota controllers.
35. Explain Kubernetes Pod Disruption Budgets (PDB).
Answer:
PDBs limit the number of voluntary disruptions allowed for a set of pods, helping maintain application availability during maintenance. PDBs are essential for maintaining high availability of critical applications by controlling disruptions from actions like upgrades or scaling.
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