Certified Kubernetes Admin Interview Questions Answers

CKA Intermediate-Level Questions

1. What is Kubernetes?
   • Kubernetes is an open-source platform designed to automate deploying, scaling, and operating application containers. It groups containers that make up an application into logical units for easy management and discovery.
2. What are the main components of the Kubernetes architecture?
   • The main components include the Control Plane (Master Node) with components like the kube-apiserver, etcd storage, kube-scheduler, kube-controller-manager, and cloud-controller-manager, and the Worker Nodes with kubelet, kube-proxy, and container runtime.
3. What is etcd in Kubernetes?
   • Etcd is a distributed key-value store used by Kubernetes to store all data used to manage the cluster state. It's crucial for Kubernetes' distributed nature and ensures data consistency and high availability.
4. How does Kubernetes scheduling work?
   • Kubernetes scheduler assigns newly created pods to nodes based on factors such as resource requirements, scheduling policies, affinity and anti-affinity specifications, taints and tolerations, and other constraints.
5. What are Kubernetes Pods?
   • Pods are the smallest deployable units in Kubernetes, which can hold one or more containers that share storage/network, and a specification on how to run the containers.
6. Explain the purpose of a ReplicaSet in Kubernetes.
   • A ReplicaSet's purpose is to maintain a stable set of replica Pods running at any given time. It ensures that a specified number of pod replicas are running at all times.
7. What is a Deployment in Kubernetes?
   • Deployments provide declarative updates for Pods and ReplicaSets. They describe a desired state in a Deployment object, and the Deployment controller changes the actual state to the desired state at a controlled rate.
8. How do you expose your application in Kubernetes?
   • You can expose your application in Kubernetes using a Service, which defines a policy by which to access the pods. Services can be exposed via different types including ClusterIP, NodePort, and LoadBalancer.
9. What is a Namespace in Kubernetes and how is it used?
   • Namespaces are a way to divide cluster resources between multiple users. They are used for creating multiple environments within the same cluster, like development, testing, and production.
10. What is a ConfigMap in Kubernetes?
    • A ConfigMap is an API object used to store non-confidential data in key-value pairs. Pods can consume ConfigMaps as environment variables, command-line arguments, or as configuration files in a volume.
11. Explain the role of a kubelet.
    • The kubelet is an agent that runs on each node in the cluster. It ensures that containers are running in a Pod.
12. What is a StatefulSet and how does it differ from a Deployment?
    • StatefulSets are used for applications that require persistent storage and unique network identifiers. Unlike Deployments, StatefulSets ensure that the naming and storage remains consistent even when the pods are rescheduled to new nodes.
13. How do you monitor the health of a Kubernetes cluster?
    • Health monitoring can be achieved using tools like Prometheus for metrics collection and Grafana for metrics visualization. Additionally, Kubernetes provides readiness and liveness probes to monitor the health of your applications.
14. What is Helm in Kubernetes?
    • Helm is a package manager for Kubernetes that allows developers and operators to more easily package, configure, and deploy applications onto Kubernetes clusters.
15. What are Kubernetes Ingresses?
    • An Ingress is an API object that manages external access to the services in a cluster, typically HTTP. Ingress can provide load balancing, SSL termination, and name-based virtual hosting.
16. What is RBAC in Kubernetes?
    • Role-Based Access Control (RBAC) is a method of regulating access to computer or network resources based on the roles of individual users within an enterprise. In Kubernetes, RBAC allows you to control who can access the Kubernetes API and what permissions they have.
17. How do you update applications in Kubernetes?
    • Applications can be updated in Kubernetes using rolling updates, which ensure zero downtime by incrementally updating pod instances with new ones. This is managed through the Deployment resource.
18. What is a DaemonSet in Kubernetes?
    • A DaemonSet ensures that all (or some) Nodes run a copy of a Pod. As nodes are added to the cluster, Pods are added to them. As nodes are removed from the cluster, those Pods are garbage collected.
19. How does Kubernetes service discovery work?
    • Kubernetes ServiceDiscovery works by assigning a unique IP address to each service, and DNS for service to service communication, which can be resolved through the cluster DNS service, enabling pods to communicate with each other.
20. What are Kubernetes Volumes?

Kubernetes volumes are storage units attached to Pods. They enable data persistence and sharing in Kubernetes across containers within the same Pod.

CKA Advance-Level Questions

1. How does Kubernetes handle node failures?
   • Kubernetes continuously checks the health of nodes using the Node Controller. If a node fails, the Replication Controller notices that pods are down and creates new ones on other available nodes, ensuring the application's availability.
2. Can you explain what a DaemonSet is and when you would use it?
   • A DaemonSet ensures that all (or some) Kubernetes nodes run a copy of a specific pod. It is commonly used for deploying system daemons like log collectors, monitoring agents, or other tools that need to run on all or certain nodes.
3. Describe the role of an Ingress controller.
   • An Ingress Controller is responsible for managing access to services in a Kubernetes cluster by processing and fulfilling the rules set in Ingress Resources. This includes routing traffic from external sources to the correct internal services and managing SSL/TLS termination.
4. What are Kubernetes ConfigMaps and Secrets used for? How do they differ?
   • ConfigMaps allow you to decouple configuration artifacts from image content to keep containerized applications portable. Secrets are similar but are used to store and manage sensitive information, such as passwords, OAuth tokens, and ssh keys. The data in Secrets is stored and handled in a more secure fashion than ConfigMaps.
5. Explain the concept of Resource Quotas in Kubernetes.
   • Resource Quotas are a tool in Kubernetes that administrators use to limit the aggregate resource consumption in a namespace. This prevents one part of the cluster from using more than its fair share of resources and helps in multi-tenant environments by ensuring equitable resource allocation.
6. How does Kubernetes use etcd?
   • Kubernetes uses etcd as a consistent and highly-available key value store to keep all cluster data. This includes the state of the cluster, pod scheduling information, and metadata. It’s critical for Kubernetes' operation, as it stores the configuration data that can be distributed among multiple nodes in the cluster.
7. What is the difference between a ReplicaSet and a Deployment in Kubernetes?
   • A ReplicaSet ensures that a specified number of pod replicas are running at any given time. However, Deployments manage ReplicaSets and provide declarative updates to applications along with features like rolling updates and rollbacks.
8. Can you explain what happens during a rolling update in Kubernetes?
   • During a rolling update, Kubernetes incrementally replaces instances of the old version of a pod with the new version without downtime. It ensures that the application remains available by carefully managing the deployment of new pods and the termination of old pods.
9. Describe the process of scaling applications in Kubernetes.
   • Scaling in Kubernetes can be performed manually by changing the number of replicas in a Deployment, or automatically using Horizontal Pod Autoscalers which adjust the number of replicas based on CPU usage or other select metrics.
10. What is the significance of labels and selectors in Kubernetes?
    • Labels are key/value pairs attached to objects, such as pods, which are used to organize and select subsets of objects. Selectors are queries that match labels and are used to determine the objects that a particular service or deployment applies to. This mechanism allows flexible and powerful grouping of related resources.