Kubernetes Cluster with Deployment

To get started with Kubernetes, visit my blog Minikube - Launch First Kubernetes Cluster and Pod

What is deployment in k8s?

• A Deployment provides a configuration for updates for Pods and replica sets.

• You describe a desired state in a Deployment, and the Deployment Controller changes the actual state to the desired state at a controlled rate.

• You can define Deployments to create new replicas for scaling or to remove existing Deployments and adopt all their resources with new Deployments.

Getting Started

YAML file

To begin with, create a deployment.yml file and write yaml code as below for a to-do application.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: todo-app
  labels:
    app: todo
spec:
  replicas: 2
  selector:
    matchLabels:
      app: todo
  template:
    metadata:
      labels:
        app: todo
    spec:
      containers:
      - name: todo
        image: rishikeshops/todo-app
        ports:
        - containerPort: 3000

The configurations are for creating 2 replicas of the todo app. Image is from docker hub, container port assigned on 3000 and added to "todo" label.

Start minikube

Secondly, start the minikube:

minikube start

Create Deployment

Then after, give the below command in the terminal:

kubectl apply -f deployment.yml

It will create deployments.

Verify with the below command:

kubectl get deployments

It will show two replicas.

Modify deployment

Now, modify the file and change the replicas to 5.

Apply the changes:

kubectl apply -f deployment.yml

It will update the configuration and create 3 more Pods.

Conclusion

To sum up, We learned how to create yaml file for deployments and commands to run it. Deploying pods and modifying them are difficult tasks, however, we can overcome them through practice, practice and practice.