# Day 32 - Kubernetes Interview Q&A

## **1\. Difference between Docker and Kubernetes**

**Docker** → Builds and runs containers.  
**Kubernetes** → Orchestrates containers across multiple nodes.

Key points:

* Docker = container runtime.
    
* Kubernetes = container orchestration tool.
    
* Kubernetes provides auto-healing, auto-scaling, load balancing.
    
* Kubernetes runs on a cluster → if one node fails, workloads shift automatically.
    

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## **2\. Main Components of Kubernetes Architecture**

### **Control Plane**

* **API Server** → Entry point for all commands.
    
* **Scheduler** → Decides which node runs a pod.
    
* **etcd** → Key-value store for cluster state.
    
* **Controller Manager** → Runs controllers like ReplicaSet, Node Controller, Job Controller.
    
* **Cloud Controller Manager** → Integrates with cloud providers (e.g., creates LoadBalancer IPs).
    

### **Worker Node**

* **kubelet** → Ensures pods run and are healthy.
    
* **kube-proxy** → Manages networking rules and service routing.
    
* **Container Runtime** → Docker, containerd, CRI-O, etc.
    

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## **3\. Docker Swarm vs Kubernetes**

**Docker Swarm**

* Simple and easy.
    
* Limited networking and scaling.
    
* Good for small workloads.
    

**Kubernetes**

* Highly scalable, flexible.
    
* Advanced networking (CNI).
    
* Large ecosystem & community.
    
* Industry standard for production.
    

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## **4\. Docker Container vs Kubernetes Pod**

* **Container** → Single isolated runtime.
    
* **Pod** → Kubernetes unit that can contain **one or more containers**.
    
* Containers in a pod share:
    
    * Network namespace
        
    * Storage volumes
        
    * Lifecycle
        

Pod = wrapper around one or more containers.

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## **5\. What is a Namespace?**

Namespace provides **logical isolation** within a Kubernetes cluster.

Use cases:

* Multi-project isolation
    
* Resource separation
    
* Independent RBAC policies
    
* Isolated services, configs, secrets
    

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## **6\. Role of kube-proxy**

kube-proxy:

* Manages network rules on nodes
    
* Updates **iptables/ipvs**
    
* Routes service traffic to appropriate pods
    
* Enables ClusterIP, NodePort, LoadBalancer traffic flow
    

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## **7\. Types of Kubernetes Services**

### **ClusterIP**

* Default type
    
* Internal access only
    
* Used for service-to-service communication
    

### **NodePort**

* Opens a port on each node
    
* External access via `NodeIP:Port`
    

### **LoadBalancer**

* Creates cloud load balancer
    
* Exposes app to the internet
    

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## **8\. Difference Between NodePort and LoadBalancer**

**NodePort**

* Access via `NodeIP:NodePort`
    
* Limited to your cluster/node network
    
* No external load balancing
    

**LoadBalancer**

* Cloud provider allocates a public IP
    
* Global reach over the internet
    
* Adds external LB + NodePort behind the scenes
    

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## **9\. Role of kubelet**

kubelet:

* Ensures pods are running
    
* Reports pod/node status to API server
    
* Restarts containers if required
    
* Handles pod lifecycle management
    

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## **10\. Day-to-Day Kubernetes Activities (DevOps Engineer)**

A strong interview-ready answer:

* Deploy and manage applications on Kubernetes
    
* Monitor cluster health and workloads
    
* Troubleshoot pod failures, service issues, networking problems
    
* Handle upgrades and maintenance of master/worker nodes
    
* Manage RBAC, namespaces, resource quotas
    
* Support developers with deployment issues
    
* Manage CI/CD pipeline deployments to Kubernetes
    
* Handle cluster security, patching, vulnerabilities
    
* Operate logging and monitoring (Prometheus, Grafana, Loki, EFK)