Welcome to Day 37 of our comprehensive guide on Kubernetes mastery! As you journey deeper into the world of container orchestration, it’s essential to arm yourself with knowledge and confidence to tackle the challenges that come your way.

So, whether you’re looking to level up your Kubernetes skills or land that dream job in the exciting world of cloud-native technologies, join us on this enlightening journey through “Kubernetes Important Interview Questions.” Let’s unlock the secrets to acing Kubernetes interviews and embark on the path to becoming a Kubernetes master!

Questions

1. What is Kubernetes and why it is important?

Kubernetes is an open-source container orchestration platform that automates the deployment, scaling, and management of containerized applications. It was originally developed by Google and is now maintained by the Cloud Native Computing Foundation (CNCF). Kubernetes provides a highly flexible and extensible architecture that allows developers and operations teams to efficiently manage containerized workloads and services.

Key reasons why Kubernetes is important:

• Automated Deployment: Kubernetes simplifies the process of deploying containers, enabling developers to focus on writing code rather than managing infrastructure.

• Scalability: It allows automatic scaling of applications based on demand, ensuring that resources are efficiently utilized without manual intervention.

• High Availability: Kubernetes ensures that applications are highly available by automatically rescheduling and recovering failed containers.

• Self-Healing: It constantly monitors the health of applications and automatically restarts or replaces unhealthy containers.

• Portability: Kubernetes abstracts away the underlying infrastructure, making it easy to deploy and run applications consistently across various cloud providers and on-premises environments.

2. What is difference between docker swarm and kubernetes?

Docker Swarm and Kubernetes are both container orchestration platforms, but they have some key differences:

• Origin and Community: Docker Swarm was developed by Docker Inc., the company behind Docker containers, while Kubernetes was developed by Google and is now a CNCF project, benefiting from a broader community.

• Architecture: Kubernetes has a more complex and flexible architecture, making it suitable for large-scale, production-grade deployments. Docker Swarm has a simpler architecture, which makes it easier to set up and get started with quickly.

• Features: Kubernetes offers a broader range of features, including advanced deployment strategies, self-healing, auto-scaling, and more, making it a robust solution for complex containerized applications. Docker Swarm focuses on simplicity and ease of use, catering to more straightforward use cases.

• Scalability: Kubernetes is known for its ability to handle large-scale deployments with thousands of nodes and containers, while Docker Swarm is generally considered better suited for smaller-scale deployments.

• Interface and CLI: Docker Swarm uses the familiar Docker CLI, making it easier for Docker users to adopt. Kubernetes has its own CLI and uses YAML manifests for defining resources, which can be more powerful and expressive.

• Community Adoption: Kubernetes has gained widespread adoption in the industry and is the de facto standard for container orchestration. Docker Swarm has a smaller user base and is often used by teams already heavily invested in the Docker ecosystem.

1. How does Kubernetes handle network communication between containers?

Kubernetes creates a virtual network that spans all the nodes in the cluster, known as the “Kubernetes Cluster Network.” This network is used to facilitate communication between containers running on different nodes.

Each pod in Kubernetes gets its unique IP address within the cluster, enabling direct communication between containers within the same pod using localhost. Pods can communicate with other pods across the cluster using their IP addresses. Kubernetes takes care of routing the network traffic between the pods using the container networking model (CNI) plugins.

Additionally, Kubernetes provides a Service abstraction, which acts as a stable endpoint to access a set of pods. Services use a load balancer to distribute incoming traffic among the pods associated with the service. This abstraction allows containers to communicate with services using the service name, regardless of which specific pod is serving the request.

1. How does Kubernetes handle scaling of applications?

Kubernetes provides two main approaches to scaling applications:

• Horizontal Pod Autoscaler (HPA): HPA automatically adjusts the number of replicas (pods) in a deployment or replica set based on observed CPU utilization or custom metrics. When the CPU utilization or custom metrics exceed the defined thresholds, Kubernetes automatically scales up the number of replicas to handle increased load. Similarly, when the load decreases, it scales down the number of replicas to conserve resources.

• Vertical Pod Autoscaler (VPA): VPA adjusts the resource requests and limits of individual pods based on their actual resource usage. It allocates more resources to pods that require additional capacity and reduces resources for pods that do not fully utilize their allocated resources.

By using these autoscaling mechanisms, Kubernetes ensures that applications can dynamically adapt to varying workloads, providing efficient resource utilization and optimal performance.

5. What is a Kubernetes Deployment and how does it differ from a ReplicaSet?

• Kubernetes Deployment: A Deployment is a higher-level abstraction that defines desired state for managing pods and replica sets. It ensures that a specified number of pod replicas are running at all times, handling updates and rollbacks efficiently. Deployments support rolling updates, allowing you to change the container image or configuration without downtime. They are commonly used for stateless applications.

• Kubernetes ReplicaSet: A ReplicaSet is a lower-level object responsible for maintaining a stable number of pod replicas. It ensures that a specified number of identical pods are running at all times, scaling the number of replicas up or down as needed. However, ReplicaSets do not support rolling updates or rollbacks, and any updates result in all old replicas being terminated and new replicas being created.

The primary difference between a Deployment and a ReplicaSet is that a Deployment provides declarative updates and rollback capabilities, making it the preferred choice for managing stateless applications with updates. On the other hand, a ReplicaSet is more suitable when you require basic scaling and a static number of replicas without the need for advanced deployment features. In practice, Deployments are commonly used, and ReplicaSets are often managed indirectly by Deployments.

1. Can you explain the concept of rolling updates in Kubernetes?

Rolling updates are a crucial feature in Kubernetes that enable seamless and controlled updates to applications deployed within the cluster. When you perform a rolling update, Kubernetes replaces old instances of a containerized application with new ones gradually, ensuring minimal downtime and maintaining a consistent state during the update process.

Here’s how the rolling update process works:

1. Pod Creation: Kubernetes creates new pods with the updated container image or configuration, ensuring the desired number of replicas is maintained.

2. Health Checks: Kubernetes monitors the health of the newly created pods using readiness probes. The new pods are not included in the service until they pass these checks.

3. Traffic Shift: Once the new pods are deemed healthy, Kubernetes gradually shifts the incoming traffic from the old pods to the new ones.

4. Termination of Old Pods: After the traffic shift is complete, Kubernetes terminates the old pods. This process continues until all the old pods have been replaced with the updated ones.

1. How does Kubernetes handle network security and access control?

Kubernetes provides several mechanisms to handle network security and access control:

• Network Policies: Kubernetes Network Policies allow you to define rules that control the flow of traffic between pods. By specifying these policies, you can isolate and secure communication between different components of your application.

• Service Accounts: Service accounts are used to grant permissions to pods within the cluster. They provide an identity for pods to interact with the Kubernetes API and other resources. Role-based access control (RBAC) is often used to manage access rights for service accounts.

• Ingress Controllers: Ingress controllers, combined with Ingress resources, enable external access to services within the cluster. Ingress resources define routing rules and perform Layer 7 (HTTP) load balancing and SSL termination, allowing you to control external access securely.

• Secrets: Kubernetes Secrets are used to securely store sensitive information, such as passwords and API keys, which are then made available to authorized pods.

By leveraging these security features, Kubernetes allows you to implement strong network security measures and restrict access to sensitive resources, protecting your applications from unauthorized access.

1. Can you give an example of how Kubernetes can be used to deploy a highly available application?

To deploy a highly available application in Kubernetes, you need to consider various aspects:

• Replicas: Ensure that your application is deployed with multiple replicas (pods). Kubernetes will automatically distribute the replicas across nodes, providing high availability in case of node failures.

• Readiness Probes: Set up readiness probes to monitor the health of your application. This ensures that only healthy replicas receive traffic.

• Horizontal Pod Autoscaler (HPA): Implement HPA to scale the number of replicas based on demand. This allows your application to handle increasing loads without manual intervention.

• Storage and Persistence: Use Persistent Volumes (PVs) and Persistent Volume Claims (PVCs) to store data persistently. This ensures that data remains available even if a pod fails or is rescheduled.

• Deployment Strategy: Employ a rolling update deployment strategy to update your application without downtime. This strategy gradually replaces old replicas with new ones, ensuring a smooth transition.

By combining these best practices and utilizing Kubernetes’ built-in features, you can deploy and manage a highly available application that can withstand failures and scale effortlessly.

1. What is namespace is kubernetes? Which namespace any pod takes if we don’t specify any namespace?

A Kubernetes Namespace is a virtual cluster within a Kubernetes cluster. It allows you to logically partition resources and provides a scope for naming uniqueness. Namespaces provide a way to organize and separate applications or teams within a shared Kubernetes cluster.

By default, if you don’t specify any namespace for a pod, it will be created in the default namespace. The default namespace is automatically created when Kubernetes is initialized and serves as the default namespace for resources when no other namespace is specified. It's essential to use namespaces to segregate resources in large or multi-tenant clusters, promoting better resource management and isolation.

1. How ingress helps in kubernetes?

In Kubernetes, Ingress is an API object that provides external access to services within the cluster. It acts as an entry point for incoming traffic and allows you to define routing rules for different services based on hostnames or paths.

Ingress is typically used with an Ingress controller, which is a Kubernetes component responsible for implementing the rules defined in the Ingress resource. The Ingress controller performs Layer 7 (HTTP) load balancing, SSL termination, and routing based on the rules specified in the Ingress resource.

Benefits of using Ingress in Kubernetes:

• Single Entry Point: Ingress provides a single entry point to access multiple services, making it easier to manage external access to various components of your application.

• Host-Based Routing: Ingress allows you to route traffic based on hostnames, enabling you to host multiple applications on the same IP address and port.

• Path-Based Routing: You can define path-based routing rules to direct incoming requests to specific services based on URL paths.

• SSL Termination: Ingress controllers can terminate SSL/TLS encryption and decrypt incoming traffic before forwarding it to the appropriate backend service.

1. Explain different types of services in kubernetes?

Kubernetes offers different types of services to expose applications running in the cluster to the internal or external network. Each service type serves a specific purpose:

• ClusterIP: This is the default service type. It exposes the service on a cluster-internal IP address reachable only from within the cluster. It allows other pods within the cluster to access the service using the service name and port.

• NodePort: This service type exposes the service on a specific port on each node’s IP address. It allows external access to the service by reaching any node on that port. Kubernetes then forwards the traffic to the appropriate service and pod.

• LoadBalancer: This service type automatically provisions an external load balancer in cloud environments that support it (e.g., AWS, GCP, Azure). The load balancer routes external traffic to the service, distributing the load across multiple pods.

• ExternalName: This type of service is used to create a DNS CNAME record that maps to an external domain name. It allows you to give a Kubernetes service an external name, effectively making the service available under the specified domain name.

• Headless Service: This service type does not create a load balancer or a ClusterIP. Instead, it sets up DNS entries for each pod of the service, allowing direct DNS-based communication with individual pods.

1. Can you explain the concept of self-healing in Kubernetes and give examples of how it works?

Self-healing is a critical aspect of Kubernetes that ensures the high availability and reliability of applications. Kubernetes monitors the health of pods and responds to failures automatically. It ensures that the desired number of replicas is maintained and takes actions to recover unhealthy pods.

Examples of how self-healing works:

• Pod Restarts: If a pod encounters a failure or becomes unresponsive, Kubernetes automatically restarts the pod to attempt recovery.

• ReplicaSets and Deployments: Kubernetes continually checks the desired number of replicas specified in the ReplicaSet or Deployment. If the actual number of replicas falls below the desired count due to pod failures or node issues, Kubernetes schedules new pods to replace the failed ones.

• Liveness Probes: Kubernetes uses liveness probes to detect the health of individual containers within a pod. If a container fails the liveness probe, Kubernetes will restart the pod to attempt recovery.

• Readiness Probes: Readiness probes ensure that a pod is ready to receive traffic. If a pod fails the readiness probe, it is removed from the service, allowing Kubernetes to route traffic to healthy pods.

By continuously monitoring the health of pods and taking corrective actions when needed, Kubernetes ensures that applications remain available and responsive, even in the face of failures.

1. How does Kubernetes handle storage management for containers?

Kubernetes provides various mechanisms for managing storage for containers:

• Volumes: Volumes are the most basic and flexible way to manage storage in Kubernetes. A volume is a directory accessible to containers in a pod and can be backed by various storage types, such as emptyDir, hostPath, PersistentVolume (PV), or cloud-based storage.

• Persistent Volumes (PVs) and Persistent Volume Claims (PVCs): PVs are cluster-wide resources that represent physical storage. PVCs are used by pods to request specific storage resources from PVs. PVs and PVCs abstract away the underlying storage details from applications, allowing for dynamic provisioning and easy migration of storage resources.

• Storage Classes: Storage classes define the storage properties and provisioners that Kubernetes uses to dynamically provision PVs. They allow you to specify different classes of storage with different characteristics and backends.

By leveraging these storage features, Kubernetes provides a unified and scalable storage management system for containers, allowing developers to handle data persistency effectively.

1. How does the NodePort service work?

A NodePort service is a type of service in Kubernetes that exposes an application externally by opening a static port on every node in the cluster. The service then forwards incoming traffic on that port to a target port on the pods.

When you create a NodePort service, Kubernetes assigns a unique port from the range 30000–32767 (by default) to the service. The service is then reachable on all nodes of the cluster at the assigned NodePort.

For example, if a NodePort service is configured with port 30080 and forwards traffic to port 80 on the pods, external clients can access the application by reaching any node’s IP address on port 30080.

NodePort services are commonly used when LoadBalancers are not available or when you need a simple way to expose your service to the external network, even if it requires direct access to specific nodes.

1. What is a multinode cluster and single-node cluster in Kubernetes?

• Multinode Cluster: A multinode cluster in Kubernetes consists of multiple nodes (servers or virtual machines) that work together to run containerized applications. Each node contributes its resources (CPU, memory, storage) to the cluster, making it suitable for production environments and scaling applications.

• Single-Node Cluster: A single-node cluster is a Kubernetes setup running on a single node. It is often used for development, testing, or learning purposes when you want to experiment with Kubernetes without the complexity of a full multinode cluster. However, single-node clusters lack the resilience and high availability that multinode clusters provide.

1. Difference between create and apply in kubernetes?

• kubectl create: The kubectl create command creates new resources based on a YAML or JSON manifest file. If the resource already exists, the command will fail, preventing you from accidentally creating duplicates. For example, you can create a deployment using kubectl create -f deployment.yaml.

• kubectl apply: The kubectl apply command creates or updates resources based on a YAML or JSON manifest file. If the resource already exists, apply will update it with the new configuration, effectively performing a patch or rolling update. Apply is idempotent, meaning you can run it multiple times without adverse effects. For example, you can create or update a deployment using kubectl apply -f deployment.yaml.

In general, kubectl create is useful for creating resources for the first time, while kubectl apply is suitable for continuous deployments and updating resources in a declarative manner. The latter is preferred for most use cases since it allows you to manage changes to resources without worrying about their current state.

17. What’s the init container and when it can be used?

Init containers will set a stage for you before running the actual POD.

Wait for some time before starting the app Container with a command like sleep 60. Clone a git repository into a volume.

18. What is the role of Load Balance in Kubernetes?

Load balancing is a way to distribute the incoming traffic into multiple backend servers, which is useful to ensure the application available to the users.

In Kubernetes, as shown in the above figure all the incoming traffic lands to a single IP address on the load balancer which is a way to expose your service to outside the internet which routes the incoming traffic to a particular pod (via service) using an algorithm known as round-robin. Even if any pod goes down load balances are notified so that the traffic is not routed to that particular unavailable node. Thus load balancers in Kubernetes are responsible for distributing a set of tasks (incoming traffic) to the pods.

19.What are the various things that can be done to increase Kubernetes security?

By default, POD can communicate with any other POD, we can set up network policies to limit this communication between the PODs.

• RBAC (Role-based access control) to narrow down the permissions.

• Use namespaces to establish security boundaries.

• Set the admission control policies to avoid running the privileged containers.

• Turn on audit logging

20. How to monitor the Kubernetes cluster?

Prometheus is used for Kubernetes monitoring. The Prometheus ecosystem consists of multiple components.

• Mainly Prometheus server which scrapes and stores time-series data.

• Client libraries for instrumenting application code.

• Push gateway for supporting short-lived jobs.

• Special-purpose exporters for services like StatsD, HAProxy, Graphite, etc.

• An alert manager to handle alerts on various support tools.

21. How to run a POD on a particular node?

Various methods are available to achieve it.

• nodeName: specify the name of a node in POD spec configuration, it will try to run the POD on a specific node.

• nodeSelector: Assign a specific label to the node which has special resources and use the same label in POD spec so that POD will run only on that node.

• nodeaffinities: required DuringSchedulingIgnoredDuringExecution, preferredDuringSchedulingIgnoredDuringExecution are hard and soft requirements for running the POD on specific nodes. This will be replacing nodeSelector in the future. It depends on the node labels.

22. What is container orchestration?

Consider a scenario where you have 5–6 microservices for an application. Now, these microservices are put in individual containers, but won’t be able to communicate without container orchestration. So, as orchestration means the amalgamation of all instruments playing together in harmony in music, similarly container orchestration means all the services in individual containers working together to fulfill the needs of a single server.

23. What is Kubectl?

Kubectl is the platform using which you can pass commands to the cluster. So, it basically provides the CLI to run commands against the Kubernetes cluster with various ways to create and manage the Kubernetes component.

24. What is Kubelet?

This is an agent service which runs on each node and enables the slave to communicate with the master. So, Kubelet works on the description of containers provided to it in the PodSpec and makes sure that the containers described in the PodSpec are healthy and running.

25. What is GKE?

GKE is Google Kubernetes Engine which is used for managing and orchestrating systems for Docker containers. GKE also lets us orchestrate container clusters within the Google Public Cloud.

26. How to set a static IP for Kubernetes load balancer?

Kubernetes Master assigns a new IP address. We can set a static IP for Kubernetes load balancer by changing the DNS records whenever Kubernetes Master assigns a new IP address.

**27. What are the tools that are used for container monitoring?

**
2. cAdvisor
3. Prometheus
4. InfluxDB
5. Grafana

28. List components of Kubernetes

1. Addons
2. Node components
3. Master Components

29. Explain Replica set

A Replica set is used to keep replica pods stable. It enables us to specify the available number of identical pods. This can be considered a replacement for the replication controller.

30. What are Secrets in Kubernetes?

Secrets are sensitive information like login credentials of the user. They are objects in Kubernetes that stores sensitive information like username and password after performing encryption.

In conclusion, We have came to an end of Kubernetes series. Day 37 of our exploration into Kubernetes important interview questions has been a journey filled with valuable insights and knowledge.

So, let’s venture forth with curiosity and determination, as we embrace the limitless possibilities that Kubernetes offers in shaping the future of computing. Happy interviewing and may your journey into the world of Kubernetes be a successful and fulfilling one!