Part 2: K3S Initial Set-Up with Linux

In the world of container orchestration, Kubernetes stands tall as the leading platform for automating deployment, scaling, and management of containerized applications.

In this guide, we’ll walk through the steps to set up and run K3s Pod on Linux.

1. Install K3s

Open your terminal and run the following command

curl -sfL https://get.k3s.io | sh -s - --write-kubeconfig-mode 644 

This command will download and install K3s on your system, and set the appropriate permissions for the kubeconfig file.

2. Set kubeconfig

Set up your kubeconfig file to communicate with the K3s cluster. This can be achieved by exporting the KUBECONFIG environment variable

bash export KUBECONFIG=/etc/rancher/k3s/k3s.yaml

3. Get Nodes

Now that K3s is installed and configured, let’s verify that everything is up and running. Run the following command to get the list of nodes in your K3s cluster.

bash kubectl get nodes

4. Create a Basic Node.js App and Dockerfile

Next, let’s create a simple Node.js application and a Dockerfile to containerize it. You can use your favourite code editor to create the following files:

app.js

const http = require('http');
const hostname = '0.0.0.0';

const port = 3000;

const server = http.createServer((req, res) => {

  res.statusCode = 200;

  res.setHeader('Content-Type', 'text/plain');

  res.end('Hello World!\n');

});

server.listen(port, hostname, () => {

  console.log(`Server running at http://${hostname}:${port}/`);

});

Dockerfile

FROM node:alpine
WORKDIR /app
COPY package.json .
RUN npm install

COPY . .

EXPOSE 3000
CMD ["node", "app.js"]

Build the Docker image

bash docker build -t my-node-app

5. Send Docker Image to K3s Docker

To deploy our Docker image to the K3s cluster, we need to import it using the k3s container (ctr) command

bash docker save my-node-app:latest | sudo k3s ctr images import

6. Create YAML File for Deployment and Service

Now, let’s create a YAML file for deploying our application and exposing it via a LoadBalancer service. Create a file named app-deployment.yaml with the following content:

yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-node-app

spec:
  replicas: 1
  selector:
    matchLabels:
      app: my-node-app
  template:
    metadata:
      labels:
        app: my-node-app
    spec:
      containers:
      - name: my-node-app
        image: my-node-app:latest
        ports:
        - containerPort: 3000
---

apiVersion: v1
kind: Service
metadata:
  name: my-node-app-service
spec:
  selector:
    app: my-node-app
  ports:
    - protocol: TCP
      port: 80
      targetPort: 3000
  type: LoadBalancer

Apply the YAML file to create the deployment and service:

bash kubectl apply -f app-deployment.yaml

7. Guide to Check Running Pod and Service, Check Logs, and Describe

Now that our application is deployed, let’s check its status, logs, and describe its details.

Check running all

bash kubectl get all

Check running pods

bash kubectl get pods

Check service:bash kubectl get svc

bash kubectl get svc

View logs

bash kubectl logs <pod-name>

Describe pod

bash kubectl describe pod <pod-name>

Great!! You are all set to leverage K3s on your server.

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