What is Kubernetes?

Learn that Kubernetes is a container orchestration platform.

What is Kubernetes?

Kubernetes (K8s) is an open-source orchestration system that runs, scales and keeps containers alive on a cluster made of many servers. Docker runs containers on a single machine; Kubernetes takes a desired state such as "3 copies of this application must always run" and makes it happen.

kubectl create deployment web --image=nginx:1.27 --replicas=3
kubectl get pods
# web-7c5b9f-abcde   1/1   Running
# web-7c5b9f-fghij   1/1   Running
# web-7c5b9f-klmno   1/1   Running

Declarative management

Kubernetes objects are usually defined in YAML files and sent to the cluster with kubectl apply. The file says "what is wanted", not "how to do it". Applying the same file again is safe; only the differences change:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: web
spec:
  replicas: 3
  ...

kubectl apply -f web.yaml

Exercise The first deployment

Write two commands: create a deployment named web with 3 replicas using the nginx:1.27 image; then list the pods.

Show example solution

kubectl create deployment web --image=nginx:1.27 --replicas=3
kubectl get pods

Test yourself

What is the core idea that separates Kubernetes from single-machine Docker?
- Running only on Windows
- Declaring a desired state and having the system keep it continuously
- Running containers faster
- Building images
Show answer

Declaring a desired state and having the system keep it continuously — If a pod crashes, Kubernetes starts a new one; you don't need to type a command.

Apply the desired state from a file.

kubectl ____ -f web.yaml

Show answer

kubectl apply -f web.yaml

Match.

cluster

A group of servers
istenen durum

What should be
kubectl

Kubernetes CLI
K8s

Kubernetes abbreviation

Next lesson: Why Kubernetes?

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