Kubernetes Introduction - K8s Tutorials

What is Kubernetes?

Kubernetes, often abbreviated as K8s, is an open-source system for automating deployment, scaling, and management of containerized applications. It was originally designed by Google and is now maintained by the Cloud Native Computing Foundation (CNCF).

Imagine you have many applications running in containers (like Docker containers). Managing them manually becomes incredibly difficult as your application grows. Kubernetes solves this by providing a framework to run distributed systems reliably and at scale.

Why Use Kubernetes?

Automation: Automates deployment, rollouts, and rollbacks.
Scalability: Easily scale applications up or down based on demand.
Self-healing: Restarts failed containers, replaces and reschedules them.
Service Discovery and Load Balancing: Exposes containers to the outside world and balances network traffic.
Storage Orchestration: Allows you to automatically mount storage systems.
Batch Execution: Manages batch and CI workloads.

Core Concepts

Pods: The smallest deployable units in Kubernetes. A Pod represents a single instance of a running process in your cluster and can contain one or more containers that share resources like network and storage.

Nodes: Worker machines (virtual or physical) that run your applications. A Kubernetes cluster consists of at least one Master node and multiple Worker nodes.

Cluster: A set of Node machines that run containerized applications managed by Kubernetes.

Deployments: A controller that manages a set of identical Pods. It's used to declare the desired state for your application, and Kubernetes will work to ensure that the actual state matches the desired state.

Services: An abstraction that defines a logical set of Pods and a policy by which to access them. Services enable communication between different parts of your application.

A Simple Example

Let's look at a very basic Deployment definition in YAML:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: 3 # We want 3 instances of our application
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:latest # The container image to use
        ports:
        - containerPort: 80

This YAML describes a Deployment that will ensure 3 replicas of a Pod are running, each running the latest Nginx image and exposing port 80.

To apply this to your cluster, you would typically use the `kubectl` command-line tool:

kubectl apply -f your-deployment.yaml

Next Steps

This was just a brief introduction. To truly master Kubernetes, you'll want to explore:

Important: Kubernetes has a steep learning curve, but the benefits in terms of scalability and resilience are immense for modern applications. Start with the basics and gradually build your understanding.