Kubernetes Overview and Architecture

Overview

This lecture series provides a comprehensive introduction to Kubernetes, covering its core concepts, architecture, important terminology, practical setup, security best practices, and key interview questions and answers.

What is Kubernetes?

• Kubernetes is an open-source tool for automating deployment, scaling, and management of containerized applications (container orchestration).
• The name "Kubernetes" means "captain" in Greek, symbolizing its role in managing many application containers.
• Developed by Google in 2014, it is now open-source and widely adopted.
• Kubernetes works with various container runtimes like Docker, containerd, and podman.
• It is essential for managing applications at large scale, providing features like self-healing, scaling, monitoring, and automated rollouts/rollbacks.

Kubernetes Architecture

• A Kubernetes cluster includes at least one Master node (Control Plane) and multiple Worker nodes.
• Master node (Control Plane) components: API server, Scheduler, Controller Manager, and etcd.
• Worker node components: kubelet, kube-proxy, and a container runtime (e.g., Docker or containerd).
• The control plane manages the state and workload scheduling; worker nodes run containers inside pods.

Core Kubernetes Concepts & Components

• Pod: The smallest unit in Kubernetes, containing one or more tightly coupled containers.
• Namespace: An isolated environment within a cluster for organizing resources.
• Deployment: Specifies the desired state for pods and manages replica sets.
• Service: Exposes sets of pods for internal/external access (ClusterIP, NodePort, LoadBalancer).
• Replica Set: Ensures a specified number of identical pods are running at all times.
• ConfigMap: Stores non-sensitive configuration data as key-value pairs.
• Ingress: Manages external access to services, usually HTTP.
• DaemonSet: Ensures a pod runs on each node.
• StatefulSet: Manages stateful applications with stable, persistent storage.

Practical Kubernetes Setup

• Minikube allows running a single-node Kubernetes cluster locally for learning and testing.
• Docker or containerd is required as the container runtime.
• Essential kubectl commands manage cluster resources: create, get, describe, delete for pods, deployments, services, etc.
• YAML files are used to define Kubernetes resources in human-readable, indented text format.

Key Kubernetes Security Practices

• Implement RBAC (Role-Based Access Control) to limit user and service account permissions.
• Use Network Policies to control traffic between pods.
• Store sensitive data using Kubernetes Secrets.
• Secure API server and etcd with TLS certificates.
• Use trusted, up-to-date container images.
• Monitor and audit with tools like Prometheus, Grafana, and audit logs.
• Follow the least privilege principle for users and services.

Interview Q&A Highlights

• Kubernetes is a container orchestration tool, not a container runtime.
• Difference between Docker (container creation) and Kubernetes (container management).
• Self-healing in Kubernetes refers to automatic restart or replacement of failed containers/pods.
• The ideal production cluster includes 3 master nodes (for high availability) and multiple worker nodes.
• Master node failure affects cluster management; redundant master nodes mitigate this.
• Each Control Plane and worker node component has specific roles and failure impacts.

Key Terms & Definitions

• Kubernetes — An open-source platform for automating containerized application management.
• Pod — The smallest deployable unit, hosting one or more containers.
• Deployment — Manages desired state and updates for pods.
• Replica Set — Maintains a set number of pod replicas.
• Service — Exposes pods as a network service.
• Namespace — Isolated cluster environment.
• DaemonSet — Ensures a pod runs on every node.
• StatefulSet — Manages stateful pods with persistent identities.
• RBAC — Role-Based Access Control for security.
• etcd — Distributed key-value store for cluster data.
• Kubelet — Node agent controlling pods/containers.
• kubectl — Command-line tool for Kubernetes management.

Action Items / Next Steps

• Practice by installing Minikube or setting up a small cluster using YAML configuration files.
• Run and become comfortable with kubectl's core commands (get, describe, create, delete).
• Experiment with different services (ClusterIP, NodePort, LoadBalancer) and deployments.
• Follow the provided GitHub repository for configuration examples and further practice.
• Review and implement security best practices in all practice and production clusters.