Top 40 Kubernetes Interview Questions and Answers 2024 Edition

Table of Content

Basic Kubernetes Interview Questions

Q.1 What is Kubernetes and what are its main components?

Kubernetes is an open-source platform designed to automate deploying, scaling, and operating application containers. Its main components include:

API Server: The central management entity that processes REST requests, validates them, and updates the corresponding objects in etcd.
etcd: A consistent and highly-available key value store used as Kubernetes’ backing store for all cluster data.
Scheduler: Responsible for distributing work or containers across multiple nodes. It selects which node an unassigned pod should run on.
Controller Manager: Runs controller processes, including node controllers, replication controllers, endpoints controllers.
Kubelet: An agent that runs on each node in the cluster. It ensures that containers are running in a pod.
Container Runtime: The software that is responsible for running containers.
Kube-Proxy: Handles Kubernetes network services on each node.

Q.2 Explain the architecture of Kubernetes.

Kubernetes follows a master-slave architecture where the master node manages the state of the cluster, and worker nodes run the actual applications:

Master Node: Contains the API Server, Scheduler, etcd, Controller Manager, and other management processes.
Worker Nodes: Each node runs Kubelet, Kube-Proxy, and a container runtime like Docker or rkt. Nodes host the Pods that are the components of the application workload.
Control Plane: Manages the state of the cluster, including scheduling workloads and maintaining the desired state.

Q.3 What is a Pod in Kubernetes?

A Pod is the smallest deployable unit created and managed by Kubernetes. A pod is a group of one or more containers, with shared storage/network, and a specification for how to run the containers. Each pod is typically isolated in its own network namespace.

Q.4 How does a Kubernetes Service work?

A Kubernetes Service is an abstraction which defines a logical set of Pods and a policy by which to access them – this might be called a micro-service. The set of Pods targeted by a Service is usually determined by a Label Selector. Services allow applications running within the cluster to communicate with each other and with the outside world.

Q.5 What is a Kubernetes Deployment and how is it different from a Pod?

A Kubernetes Deployment provides declarative updates for Pods and ReplicaSets. It allows you to describe an application’s life cycle, such as which images to use for the app, the number of pods, and how they should be updated. Deployments manage the state of ReplicaSets and Pods, making sure that the number of actual instances matches the desired state defined in the Deployment. A Pod, by contrast, represents a single instance of a running process in your cluster.

Q.6 How does Kubernetes achieve High Availability (HA)?

Kubernetes achieves HA by running multiple master nodes and ensuring that the Kubernetes API Server is accessible at any time. etcd, which stores the state of the Kubernetes cluster, is also typically configured in a high-availability setup to prevent a single point of failure.

Q.7 What is the role of kubelet in Kubernetes?

Kubelet is an agent that runs on each node in the Kubernetes cluster. It makes sure that containers are running in a Pod. It takes a set of PodSpecs that are provided through various mechanisms and ensures that the containers described in those PodSpecs are running and healthy.

Q.8 What is a Kubernetes Namespace and why is it used?

Namespaces in Kubernetes are used to organize objects in the cluster and provide a way to divide cluster resources between multiple users. They are used extensively in environments with many users spread across multiple teams or projects.

Q.9 How does Kubernetes manage storage?

Kubernetes manages storage through Volumes and Persistent Volumes. Volumes provide temporary storage that lives as long as the Pod that encloses it. Persistent Volumes (PVs) provide a file system that can be mounted to the cluster, without being tied to the life cycle of any individual Pod. Persistent Volume Claims (PVCs) allow users to request specific sizes and types of persistent storage.

Q.10 What is a Kubernetes Secret and how is it used?

A Kubernetes Secret is an object that contains a small amount of sensitive data such as a password, a token, or a key. Such information might otherwise be put in a Pod specification or in an image. Secrets give you a more flexible and more secure alternative to putting confidential data directly into the Pod definition or a Docker image.

Q.11 How does Kubernetes manage networking between Pods?

Kubernetes assigns each Pod its own IP address, so you do not need to explicitly create links between Pods and you almost never need to deal with mapping container ports to host ports. This creates a clean, backward-compatible model where Pods can be treated much like VMs or physical hosts from the perspectives of port allocation, networking, naming, service discovery, load balancing, application configuration, and migration.

Q.12 Explain the role of etcd in Kubernetes.

etcd is a consistent and highly-available key value store used as Kubernetes’ backing store for all cluster data. It stores the configuration data of the cluster and represents the state of the cluster at any given point of time. Kubernetes components watch for changes to this store to bring themselves into the desired state.

Q.13 What are Labels and Selectors in Kubernetes?

Labels are key/value pairs that are attached to objects, such as Pods. Labels are used to organize and to select subsets of objects. Selectors are used in Kubernetes to find and group resources based on their labels. This is especially useful when you need to manage subsets of resources as a single unit.

Q.14 How does rolling updates work in Kubernetes?

Rolling updates allow Deployments’ updates to take place with zero downtime by incrementally updating Pods instances with new ones. The new Pods will be scheduled on Nodes with available resources. Rolling updates allow for rollback to previous versions if issues are detected.

Q.15 What is a Kubernetes ConfigMap?

A Kubernetes ConfigMap is a key-value store for non-confidential data in a distributed system. Your application and system components can store configuration artifacts as a ConfigMap object and query this object to retrieve data.

Q.16 How does Horizontal Pod Autoscaling (HPA) work in Kubernetes?

HPA automatically scales the number of Pod replicas based on observed CPU utilization or other select metrics provided by the user. The HPA is implemented as a Kubernetes API resource and a controller. The controller periodically adjusts the number of replicas in a ReplicaSet or Deployment to match the observed metrics to the user-defined targets.

Q.17 What is the role of a Container Runtime in Kubernetes?

The container runtime is the software that is responsible for running containers. Kubernetes supports several container runtimes: Docker, containerd, CRI-O, and any implementation of the Kubernetes CRI (Container Runtime Interface).

Q.18 How does Kubernetes manage security?

Kubernetes provides several mechanisms to impart strong security including Network Policies, Pod Security Policies, Role-based Access Control, Node Security, and Security Contexts. These all work in unison to provide a comprehensive security framework for managing the operations of services and Pods.

Q.19 What are StatefulSets in Kubernetes?

StatefulSets are Kubernetes controllers that manage stateful applications. They manage the deployment and scaling of a set of Pods, and provide guarantees about the ordering and uniqueness of these Pods. Unlike a Deployment, a StatefulSet maintains a sticky identity for each of their Pods. These Pods are created from the same specification, but are not interchangeable: each has a persistent identifier that it maintains across any rescheduling.

Q.20 How does Kubernetes handle service discovery?

Kubernetes supports service discovery natively using DNS. When you create a Service, Kubernetes creates a DNS entry that can be queried to reach the Pods backing that Service. Clients perform DNS queries to discover endpoints where specific services can be accessed.

Intermediate Kubernetes Interview Questions

Q.21 What are Taints and Tolerations in Kubernetes?

Taints and tolerations work together to ensure that pods are not scheduled onto inappropriate nodes. A taint is applied to a node to mark it as unsuitable for certain pods, while a toleration is applied to a pod to allow it to be scheduled onto a node with a matching taint. This mechanism is used to ensure that specific nodes are reserved for particular workloads, such as sensitive security tasks or hardware-intensive processes.

Q.22 How does Kubernetes perform load balancing?

Kubernetes performs load balancing through Services and Ingress:

Services manage internal load balancing by providing a single point of access for a set of pods and distributing network traffic among them.
Ingress manages external access to the services within a cluster, providing features like load balancing, SSL termination, and name-based virtual hosting via external load balancers or Kubernetes Ingress Controllers.

Q.23 Explain the role of a Kubernetes Operator.

A Kubernetes Operator is a method of packaging, deploying, and managing a Kubernetes application. Operators extend Kubernetes’ native APIs and manage complex stateful applications as if they were native Kubernetes components. They automate tasks like deployments, updates, backups, and scaling, which would normally require human intervention or scripts.

Q.24 What are Persistent Volumes (PV) and Persistent Volume Claims (PVC)?

Persistent Volumes (PVs) are storage resources in a cluster that are provisioned by an administrator and exist independently of pod lifecycles. They represent a piece of storage in the cluster that has been provisioned by an administrator or dynamically provisioned using Storage Classes.
Persistent Volume Claims (PVCs) are requests for storage by a user. They specify size, and access modes like read/write once or read/write many. PVCs request specific storage resources defined by a PV, and once bound, the PVC locks the PV resources so that it is exclusively used by that claim.

Q.25 How does rolling back deployments work in Kubernetes?

Rolling back in Kubernetes is performed by the Deployment controller. If a Deployment is updated with a new configuration that is not desirable or fails, Kubernetes allows you to revert to a previous deployment version. This is achieved by changing the Deployment to reflect the previous successful state, managed automatically by the system.

Q.26 What is a Kubernetes CronJob?

A CronJob in Kubernetes creates Jobs on a time-based schedule, similar to the cron utility in Linux. It runs a job periodically on a given schedule, written in Cron format. This is useful for performing maintenance and backup tasks, report generation, or sending emails at specific times.

Q.27 How does Kubernetes manage configuration and secrets rotation?

Kubernetes manages configurations through ConfigMaps and secrets through Secrets objects. Both can be updated dynamically, and applications can be configured to restart or reload configuration when changes occur. Secrets can be rotated by creating new ones and updating the pod specification to use the new version, thereby enhancing security.

Q.28 What are Init Containers and when are they used?

Init containers are specialized containers that run before application containers in a Pod. They contain utilities or setup scripts not present in an app image. They must complete successfully before the application containers start. Examples include setting up a work environment, initializing config files, or waiting for other services that the app needs to be fully operational.

Q.29 How does Pod scheduling work in Kubernetes?

Pod scheduling in Kubernetes involves the Scheduler selecting an optimal node for the pod to run on based on various criteria, such as available resources, node policies, and affinity/anti-affinity specifications. The Scheduler places the pod on the most appropriate node that satisfies the pod’s requirements while maintaining resource allocation balance across the cluster.

Q.30 What is PodAffinity and PodAntiAffinity in Kubernetes?

PodAffinity and PodAntiAffinity are policies that instruct the Kubernetes scheduler about the placement of pods relative to other pods. PodAffinity encourages the scheduler to place pods together based on labels if they attract each other. Conversely, PodAntiAffinity discourages or prevents placing pods together if they repel each other, improving fault tolerance and spreading pods across nodes.

Advanced Kubernetes Interview Questions

Q.31 What is the difference between a Service and an Ingress in Kubernetes?

A Service in Kubernetes is an abstraction that defines a logical set of Pods and a policy by which to access them. Services enable network access to a set of Pods, typically without exposing them directly to the external network. Ingress, on the other hand, manages external access to the services, providing features like load balancing, SSL termination, and name-based virtual hosting. Ingress exposes HTTP and HTTPS routes from outside the cluster to services within the cluster.

Feature	Service	Ingress
Purpose	Provides a way to access pods within a cluster using a single, stable IP address or DNS name.	Manages external access to the services within the cluster, typically HTTP/HTTPS.
Scope	Primarily used for internal traffic within the Kubernetes cluster.	Primarily handles external traffic coming into the cluster.
Functionality	Can perform basic load balancing across multiple pods.	Provides advanced routing, SSL termination, and name-based virtual hosting.
Configuration	Targets pods based on selector labels and distributes traffic among them.	Uses rules to control the routing of external traffic to services.
Use Case	Ideal for discovering services within the cluster or simple load balancing without path or host-based routing.	Used when you need to expose multiple services to the external network under a single IP address with specific routing rules.
Protocols	Supports TCP, UDP, and any other protocol supported by the underlying network.	Typically focused on HTTP/HTTPS traffic, though extensions may support other protocols.
Resource Type	A native Kubernetes API object.	A Kubernetes API object that may depend on an Ingress Controller to implement the actual traffic routing.

Q.32 How does Kubernetes handle pod-to-pod communication across nodes?

Kubernetes handles pod-to-pod communication across nodes using the kube-proxy, which runs on each node. Kube-proxy maintains network rules that allow communication to and from pods across the cluster regardless of the node they reside on. This is supported by the network plugin that implements the Cluster Network Interface (CNI), ensuring all pods can communicate with each other without NAT.

Q.33 Explain Kubernetes Federation and when it is used.

Kubernetes Federation allows managing multiple Kubernetes clusters as if they were a single cluster. Federation is useful in scenarios where clusters are spread across multiple datacenters or cloud providers. It helps in cross-cluster synchronization of resources, improving global load balancing, redundancy, and failover by spreading the workload across clusters and regions.

Q.34 What is Pod Disruption Budget (PDB) and how does it work?

A Pod Disruption Budget (PDB) limits the number of Pods of a replicated application that are down simultaneously during voluntary disruptions (e.g., maintenance). For example, if a service requires high availability and has 10 replicas running, a PDB can ensure that only a certain percentage or a specific number of pods may be down at the same time.

Q.35 How does Kubernetes manage Stateful Applications?

Kubernetes manages stateful applications through StatefulSets, which is a workload API object used to manage stateful applications. Unlike Deployments, StatefulSets maintain a sticky identity for each of their Pods. They manage the deployment and scaling of a set of Pods, and provide guarantees about the ordering and uniqueness of these Pods.

Q.36 What is the difference between a Job and a CronJob in Kubernetes?

A Job creates one or more Pods and ensures that a specified number of them successfully terminate. Jobs are used to run individual tasks to completion. A CronJob, on the other hand, manages time-based Jobs, i.e., it schedules Jobs to run periodically at fixed times/dates. This is similar to cron in Unix-like systems.

Q.37 How does Kubernetes handle multi-tenancy?

Kubernetes handles multi-tenancy primarily through Namespaces, which partition cluster resources between multiple users. Additionally, Kubernetes uses Resource Quotas and Network Policies to isolate resources and traffic of different tenants. Role-Based Access Control (RBAC) is also used to control what actions tenants can perform.

Q.38 What are Custom Resource Definitions (CRDs) in Kubernetes?

Custom Resource Definitions (CRDs) allow you to define new types of resources that act like native Kubernetes objects. CRDs are powerful tools that extend Kubernetes capabilities by allowing developers to add custom information or functionality not provided by the default resource types.

Q.39 How does Kubernetes handle cluster upgrades?

Kubernetes handles cluster upgrades using a process that involves updating the software on each node in the cluster. Tools like kubeadm can be used to upgrade Kubernetes clusters. The control plane nodes are upgraded first, followed by worker nodes, to ensure continuous management and operation of the cluster.

Q.40 Explain the concept of Kubernetes Operators and give examples.

Kubernetes Operators are software extensions that use custom resources to manage applications and their components. Operators follow Kubernetes principles, notably the control loop, to manage specific applications. Examples include the Prometheus Operator for managing Prometheus monitoring instances, or the etcd Operator for managing etcd clusters.

Official Website of Kubernetes : https://kubernetes.io/