DEV Community: Cheulong Sear

How to set up k3s on Ubuntu server

Cheulong Sear — Tue, 03 Feb 2026 07:36:00 +0000

What is k3s?

Prerequisite

Servers
Fixed Registration Address
Option: Worker node

Create the control plane

run this script to create a control plane

curl -sfL https://get.k3s.io | sh -

Create the worker node

To join a worker node to your existing k3s control plane, you need two things from the control-plane node:

The node token
The control-plane node’s IP or hostname

1. Get the node token (on the control-plane node)

Run this on the machine where you installed k3s with your command:

sudo cat /var/lib/rancher/k3s/server/node-token

Copy this value.

2. Join the worker node

On the worker node, run:

curl -sfL https://get.k3s.io | K3S_URL=https://<CONTROL_PLANE_IP>:6443 K3S_TOKEN=<NODE_TOKEN> sh -

Example:

curl -sfL https://get.k3s.io | \
  K3S_URL=https://192.168.1.10:6443 \
  K3S_TOKEN=K10f3a9c7c0f2e7c8d9b3b1a2c3d4e5f6::server:abcdef1234567890 \
  sh -

Verify the worker joined

Back on the control-plane node:

kubectl get nodes

You should see something like:

NAME           STATUS   ROLES                  AGE   VERSION
master-1       Ready    control-plane,master   5m    v1.xx.x+k3s
worker-1       Ready    <none>                  1m    v1.xx.x+k3s

Optional copy kubeconfig to personal pc

On the control-plane node

sudo cp /etc/rancher/k3s/k3s.yaml /tmp/k3s.yaml
sudo chown $USER:$USER /tmp/k3s.yaml

On your Ubuntu Desktop

scp user@192.0.0.1:/tmp/k3s.yaml ~/.kube/config
chmod 600 ~/.kube/config

Edit ONLY the server line

nano ~/.kube/config

change

server: https://127.0.0.1:6443

# to

server: https://<control-plane-ip>:6443

verification

kubectl config get-contexts
kubectl cluster-info
kubectl get nodes

Troubleshooting

hostname collusion

On control plane, Run :

sudo systemctl status k3s-agent

if you see 403 unable to verify password for node ubuntu-server
you might need to change worker-node's hostname
on worker node

# change hostname to worker-1

sudo systemctl stop k3s-agent || true
sudo /usr/local/bin/k3s-agent-uninstall.sh || true
sudo rm -rf /var/lib/rancher/k3s
sudo rm -rf /etc/rancher

sudo hostnamectl set-hostname worker-1
exec bash

On the CONTROL PLANE — remove the old node entry

kubectl delete node ubuntu-server || true

Also verify the token:

sudo cat /var/lib/rancher/k3s/server/node-token

Rejoin the worker with the correct token
On the worker node:

curl -sfL https://get.k3s.io | \
  K3S_URL=https://<CONTROL_PLANE_IP>:6443 \
  K3S_TOKEN=<NODE_TOKEN> \
  sh -

sudo systemctl restart k3s-agent

=== Done ===

Leave a comment if you have any questions.

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Your first gRPC API in Node.js

Cheulong Sear — Mon, 02 Feb 2026 05:08:00 +0000

Convert Rest API to gRPC

Why use gRPC?

gRPC is a high-performance, open-source universal RPC framework that runs natively on microservices and serverless architectures.

Example

Rest API

Here is a simple example of a Rest API of restaurant service that return list of restaurants based on restaurant ids.

#restaurant-service

import express from "express";

const app = express();
app.use(express.json());  

const restaurantsData = [
  {
    id: "res_001",
    name: "Spicy Garden",
    cuisine: "Indian",
    location: "New York",
    rating: 4.5,
    isOpen: true,
  },
  {
    id: "res_002",
    name: "Sushi Zen",
    cuisine: "Japanese",
    location: "San Francisco",
    rating: 4.7,
    isOpen: false,
  },
  {
    id: "res_003",
    name: "Pasta Palace",
    cuisine: "Italian",
    location: "Chicago",
    rating: 4.2,
    isOpen: true,
  },
  {
    id: "res_004",
    name: "Burger Hub",
    cuisine: "American",
    location: "Austin",
    rating: 4.0,
    isOpen: true,
  },
  {
    id: "res_005",
    name: "Dragon Wok",
    cuisine: "Chinese",
    location: "Seattle",
    rating: 4.6,
    isOpen: false,
  },
];

app.post("/restaurants/bulk", (req, res) => {
  const { restaurantIds } = req.body;

  const result = restaurantsData.filter(r =>
    restaurantIds.includes(r.id)
  );

  res.json(result);
});

app.listen(3001, () => {
    console.log("Server is running on port 3001");
});

To convert this Rest API to gRPC, we need to define a .proto file.

.proto file is a language-neutral, platform-neutral, and protocol-neutral interface definition language (IDL) that defines the service and message formats.
See the doc for more details: https://protobuf.dev/programming-guides/proto3/

  #restaurants.proto

  syntax = "proto3";

  package restaurants;

  service RestaurantService {
      rpc GetRestaurantsBulk (BulkRestaurantRequest) returns (BulkRestaurantResponse);
  }

  message BulkRestaurantRequest{
      repeated string restaurantIds = 1;
  }

  message Restaurant {
    string id = 1;
    string name = 2;
    string cuisine = 3;
    string location = 4;
    double rating = 5;
    bool isOpen = 6;
  }

  message BulkRestaurantResponse {
    repeated Restaurant restaurants = 1;
  }

a gRPC server that replaces your Express route

Install dependencies

  bun add @grpc/grpc-js @grpc/proto-loader

#restaurant-service/grpc-server.js

import grpc from "@grpc/grpc-js";
import protoLoader from "@grpc/proto-loader";
import path from "path";

const PROTO_PATH = path.resolve("restaurants.proto");

// Load proto
const packageDefinition = protoLoader.loadSync(PROTO_PATH, {
  keepCase: true,
  longs: String,
  enums: String,
  defaults: true,
  oneofs: true,
});

const restaurantProto =
  grpc.loadPackageDefinition(packageDefinition).restaurants;
;

// Mock data (same as Express)
const restaurantsData = [
  {
    id: "res_001",
    name: "Spicy Garden",
    cuisine: "Indian",
    location: "New York",
    rating: 4.5,
    isOpen: true,
  },
  {
    id: "res_002",
    name: "Sushi Zen",
    cuisine: "Japanese",
    location: "San Francisco",
    rating: 4.7,
    isOpen: false,
  },
  {
    id: "res_003",
    name: "Pasta Palace",
    cuisine: "Italian",
    location: "Chicago",
    rating: 4.2,
    isOpen: true,
  },
  {
    id: "res_004",
    name: "Burger Hub",
    cuisine: "American",
    location: "Austin",
    rating: 4.0,
    isOpen: true,
  },
  {
    id: "res_005",
    name: "Dragon Wok",
    cuisine: "Chinese",
    location: "Seattle",
    rating: 4.6,
    isOpen: false,
  },
];

// gRPC method implementation
function getRestaurantsBulk(call, callback) {
  const { restaurantIds } = call.request;

  const restaurants = restaurantsData.filter(r =>
    restaurantIds.includes(r.id)
  );

  callback(null, { restaurants });
}

// Create server
const server = new grpc.Server();

server.addService(restaurantProto.RestaurantService.service, {
  GetRestaurantsBulk: getRestaurantsBulk,
});

// Start server
server.bindAsync(
  "0.0.0.0:50051",
  grpc.ServerCredentials.createInsecure(),
  (port, error) => {
    if(error){
      console.log("Error binding server", error);
      return;
    }
    console.log("gRPC Server running on port ", port);
    server.start();
  }
);

Create a gRPC client that replaces your Express client that returns list of restaurants based on restaurant ids that user visited.


#user-service/grpc-server.ts

import express from 'express';
import grpc from "@grpc/grpc-js";
import protoLoader from "@grpc/proto-loader";
import path from "path";

const app = express();

// Load proto
const PROTO_PATH = path.resolve("restaurants.proto");

const packageDefinition = protoLoader.loadSync(PROTO_PATH, {
  keepCase: true,
  longs: String,
  enums: String,
  defaults: true,
  oneofs: true,
});

const restaurantProto: any =
  grpc.loadPackageDefinition(packageDefinition).restaurants;

const restaurantClient = new restaurantProto.RestaurantService(
  "localhost:50051",
  grpc.credentials.createInsecure()
);

const userData = [{
  id: 'user_001',
  name: 'John Doe',
  email: 'john.doe@example.com',
  vistedRestaurant: [
    'res_001',
    'res_002',
    'res_003'
  ]
}];

app.get('/users/:id/visit-restaurants', async (req, res) => {
  const userId = req.params.id;
  const userDetailData = userData.find((user) => user.id === userId);

  restaurantClient.GetRestaurantsBulk(
    {
      restaurantIds: userDetailData?.vistedRestaurant,
    },
    (err: grpc.ServiceError | null, response: any) => {
      if (err) {
        console.error(err);
        return res.status(500).json({ message: "gRPC error" });
      }

      res.json({
        visitedRestaurantsDetail: response.restaurants,
      });
    }
  );
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});

Express	gRPC
POST /restaurants/bulk	GetRestaurantsBulk RPC
req.body.restaurantIds	call.request.restaurantIds
res.json(result)	callback(null, { restaurants })
JSON over HTTP	Protobuf over HTTP/2

Other Benefits

Performance: gRPC is faster than REST because it uses binary encoding and HTTP/2, which allows for better compression and faster data transfer.
Security: gRPC supports authentication and authorization, which makes it more secure than REST.
Scalability: gRPC is designed to handle high traffic and large data sets, which makes it more scalable than REST.

Drawbacks

Learning Curve: gRPC has a steeper learning curve than REST, which can make it more difficult to learn and implement.
Tooling: gRPC has limited tooling support compared to REST, which can make it more difficult to debug and test.
Flexibility: gRPC is less flexible than REST, which can make it more difficult to adapt to changing requirements.

Conclusion

gRPC is a powerful and efficient way to build microservices, but it is not a one-size-fits-all solution. It is best used for high-performance, low-latency, and high-throughput applications.

=== Done ===

Code for this article

Leave a comment if you have any questions.

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Justfile make your life easier

Cheulong Sear — Sun, 01 Feb 2026 07:48:18 +0000

What is `Just`?

just is a handy way to save and run project-specific commands.
Commands, called recipes, are stored in a file called justfile with syntax inspired by make.

Why use `Just`?

just gives you cleaner, safer, more portable project commands than ad-hoc shell scripts or long README copy-paste commands.

just has a ton of useful features, and many improvements over make:

just is a command runner, not a build system, so it avoids much of make's complexity and idiosyncrasies. No need for .PHONY recipes!
Linux, MacOS, Windows, and other reasonable unices are supported with no additional dependencies. (Although if your system doesn't have an sh, you'll need to choose a different shell.)
Errors are specific and informative, and syntax errors are reported along with their source context.
Recipes can accept command line arguments.
Wherever possible, errors are resolved statically. Unknown recipes and circular dependencies are reported before anything runs.
just loads .env files, making it easy to populate environment variables.
Recipes can be listed from the command line.
Command line completion scripts are available for most popular shells.
Recipes can be written in arbitrary languages, like Python or NodeJS.

And much more!

Installation

just should run on any system with a reasonable sh, including Linux, MacOS, and the BSDs.

For Ubuntu:

sudo apt install just

Example

Here is the example of just with vitest in bun:

# sum.ts

console.log('environment is', process.env.NODE_ENV);

export const sum = (a: number, b: number) => {
    return a + b;
}

console.log(sum(1, 2));

# sum.test.ts

import { expect, test } from 'vitest'
import { sum } from './sum.ts'

test('adds 1 + 2 to equal 3', () => {
  expect(sum(1, 2)).toBe(3)
})

  "scripts": {
    "start": "bun run sum.ts",
    "test": "vitest"
  }

Create justfile in the root directory of the project:

default:
    just --list --unsorted

start:
    bun run start

test:
    vitest

Run just:

just

just start

just test

Other Arguments

Env

For example, if your .env file contains:

DATABASE_ADDRESS=localhost:6379
SERVER_PORT=1337

And your justfile contains:

set dotenv-load

serve:
  @echo "Starting server with database $DATABASE_ADDRESS on port $SERVER_PORT…"
  ./server --database $DATABASE_ADDRESS --port $SERVER_PORT

just serve will output:

$ just serve
Starting server with database localhost:6379 on port 1337…
./server --database $DATABASE_ADDRESS --port $SERVER_PORT

### Export

The export setting causes all just variables to be exported as environment variables. Defaults to false.

set export

a := "hello"

@foo b:
  echo $a
  echo $b

$ just foo goodbye
hello
goodbye

Positional Arguments

If positional-arguments is true, recipe arguments will be passed as positional arguments to commands. For linewise recipes, argument $0 will be the name of the recipe.

For example, running this recipe:

set positional-arguments

@foo bar:
  echo $0
  echo $1

Will produce the following output:

$ just foo hello
foo
hello

=== Done ===

Leave a comment if you have any questions.

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End-to-End DevSecOps Project (Movies Finder)

Cheulong Sear — Sun, 23 Nov 2025 14:18:39 +0000

Overview

Project: End-to-End DevSecOps Project (Movies Finder)

Overview While the visible application is a React-based Movie Finder (consuming TMDB API), this project serves as a comprehensive proof-of-concept for a production-grade DevSecOps lifecycle. It demonstrates the automated delivery of a secure, tested, and monitored web application onto a baremetal Kubernetes cluster using GitOps principles.

Goal To architect a "Zero-Touch" delivery pipeline that automates the build, testing, security scanning, and deployment processes, ensuring that only high-quality, secure code reaches production without manual intervention.

Tech Stack & Tools

Infrastructure & GitOps: Kubernetes, Docker, Helm, ArgoCD, Baremetal Homelab
CI/CD & Release: GitLab CI/CD, Release-it, Commitizen, Husky, Lint-Staged
Observability Stack: OpenTelemetry, Prometheus, Grafana, Alloy, Alertmanager, Slack
Security (DevSecOps): Trivy, OWASP ZAP, Gitleaks, Sealed-Secrets, Syft (SBOM)
Testing & QA: Playwright (E2E), Vitest (Unit), SonarCloud

Key Results & Achievements

Optimized Release Cycle: Automated the entire delivery chain, reducing deployment turnaround time by 50% (from 40m to 20m) while adding comprehensive testing and security stages.
360° Observability: Implemented the "Grafana Alloy" & OpenTelemetry stack to correlate metrics and logs, providing real-time performance monitoring and instant Slack alerts for node resource exhaustion.
Automated Compliance Gates: Shifted security left by integrating Trivy (container scanning) and Dependency Checkinto the CI pipeline, automatically blocking builds with critical CVEs.
Zero-Downtime Deployment: Leveraged ArgoCD to manage state drift and ensure seamless application updates via GitOps.

Check full article: https://cheulongsear.dev/projects/deploying-movies-finder

Leave a comment if you have any questions.

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How to set up Slack notifications from GitLab CI/CD using the Slack API

Cheulong Sear — Thu, 30 Oct 2025 13:04:43 +0000

Learn how to integrate Slack with GitLab CI/CD to receive real-time build and deployment notifications directly in your Slack channels. This step-by-step guide walks you through creating a Slack app, configuring the Slack API, and setting up GitLab pipeline jobs to send custom messages for successful builds, failures, and more.

Create a Slack App

1.Go to https://api.slack.com/apps

After signin

2.Click Create New App → From Scratch

3.Give it a name (e.g., GitLab CI Notifier)
4.Choose your workspace

5.Create App

You can add App Icon and App name here

Add Incoming Webhooks

1.In the left sidebar, go to Features → Incoming Webhooks

2.Toggle Activate Incoming Webhooks → ON

3.Click Add New Webhook to Workspace
4.Choose a channel or private group where messages should be sent

5.Copy the Webhook URL:

https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX

Store the Webhook URL in GitLab

1.Go to your GitLab project → Settings → CI/CD → Variables

2.Add a variable:

Edit your .gitlab-ci.yaml

Add a job that sends a message to Slack:

stages:
  - slack_notify

notify_slack:
  stage: slack_notify
  tags:
    - linux-homelab-general-vm
  image:
    name: alpine:latest
  before_script:
    - apk add --no-cache curl
  script:
    - |
      MESSAGE="✅ Pipeline $CI_PIPELINE_STATUS for project $CI_PROJECT_NAME on branch $CI_COMMIT_REF_NAME – $CI_COMMIT_SHORT_SHA"
      echo "Sending Slack notification: $MESSAGE"
      curl -X POST -H 'Content-type: application/json' --data "{\"text\":\"$MESSAGE\"}" "$SLACK_WEBHOOK"
  when: always

=== Done ===

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Setup cert-manager in local K8s cluster using nginx-ingress & Cloudflare DNS

Cheulong Sear — Wed, 29 Oct 2025 22:45:29 +0000

Step:

Apply nginx deployment
Apply nginx clusterIp service
Install ingress-nginx
Setup Local domain name pointing to Load Balancer IP
Create the Cloudflare API token
Setup cert-manager
Enable TLS on ingress

Prerequisite:

MetalLB is already set up in this local k8s cluster.

1.Apply nginx deployment

cat <<EOF > nginx-deploy.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.27
        ports:
        - containerPort: 80
EOF

kubectl apply -f nginx-deploy.yaml

2.Apply nginx clusterIp service

cat <<EOF > nginx-svc.yaml
apiVersion: v1
kind: Service
metadata:
  name: nginx-service
spec:
  type: ClusterIP
  selector:
    app: nginx
  ports:
    - port: 80
      targetPort: 80
EOF

kubectl apply -f nginx-svc.yaml

3.Install ingress-nginx

Next we will install ingress-nginx using helm

helm upgrade --install ingress-nginx ingress-nginx \
  --repo https://kubernetes.github.io/ingress-nginx \
  --namespace ingress-nginx --create-namespace

set up ingress pointing to nginx service

cat <<EOF > ingress-svc.yaml
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: ingress-nginxservice
  namespace: default
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  ingressClassName: nginx
  rules:
  - host: nginx.cheulong-homelab.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
                name: nginx-service
                port:
                  number: 80

EOF

kubectl apply -f ingress-svc.yaml

4.Setup Local domain name pointing to Load Balancer IP

If you go to http://192.168.186.241 now you will see 404 error, it means ingress works correctly, we need to setup domain name to point to that IP.

Type sudo nano /etc/hosts and add like below

now go to http://nginx.cheulong-homelab.com

Next step, we need to use cert-manager to generate the certificate for this domain.

5.Create the Cloudflare API token

1.Log in to Cloudflare Dashboard https://dash.cloudflare.com/
2.Click your profile icon (top right) → “My Profile”
3.Go to API Tokens → click “Create Token”
4.Choose “Edit zone DNS” template
5.Under “Permissions”, make sure it includes:
Zone | DNS | Edit
6.Under “Zone Resources”, choose: Include | All zones

7.Click Continue to summary → Create Token
8.Copy the generated token and keep it safe, you’ll only see it once.

6.Setup cert-manager

1.deploy the cert-manager using helm

helm install \
  cert-manager oci://quay.io/jetstack/charts/cert-manager \
  --version v1.19.1 \
  --namespace cert-manager \
  --create-namespace \
  --set crds.enabled=true

2.deploy letsencrypt cluster issuer

Create secret for cloudflare token api

kubectl create secret generic cloudflare-api-token-secret \
  --from-literal=api-token='cfapi_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx' \
  -n cert-manager

Let's encrypt will use cloudflare dns to verify the ownership.

cat <<EOF > cluster-issuer.yaml
apiVersion: cert-manager.io/v1
kind: ClusterIssuer
metadata:
  name: letsencrypt-dns
spec:
  acme:
    email: searcheulong@gmail.com
    server: https://acme-v02.api.letsencrypt.org/directory
    privateKeySecretRef:
      name: letsencrypt-dns-key
    solvers:
    - dns01:
        cloudflare:
          apiTokenSecretRef:
            name: cloudflare-api-token-secret
            key: api-token
    # Add additional solvers here if needed
    # - http01:
    #     ingress:
    #       ingressClassName: nginx
EOF

kubectl apply -f cluster-issuer.yaml

3.deploy the certificate

cat <<EOF > cert.yaml
apiVersion: cert-manager.io/v1
kind: Certificate
metadata:
  name: cheulong-nginx-cert
  namespace: default
spec:
  secretName: cheulong-nginx-tls
  dnsNames:
    - nginx.cheulong-homelab.com
  issuerRef:
    name: letsencrypt-dns
    kind: ClusterIssuer
EOF

kubectl apply -f cert.yaml

You can check the detail

The tls also was created

7.Enable TLS on ingress

cat <<EOF > ingress-svc.yaml
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: ingress-nginxservice
  namespace: default
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  tls: 
  - hosts:
    - nginx.cheulong-homelab.com
    secretName: cheulong-nginx-tls
  ingressClassName: nginx
  rules:
  - host: nginx.cheulong-homelab.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
                name: nginx-service
                port:
                  number: 80

EOF

kubectl apply -f ingress-svc.yaml

Now if you type https://nginx.cheulong-homelab.com/, it will connect successfully.

=== Done ===

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Expose the Kubernetes Load Balancer on Bare Metal using MetalLB

Cheulong Sear — Tue, 14 Oct 2025 18:54:49 +0000

This article will show you how to install MetalLB in K8s and expose a load balancer in your network.
Please refer to the official doc for more detail.

Preparation

If you’re using kube-proxy in IPVS mode, since Kubernetes v1.14.2 you have to enable strict ARP mode.
run

kubectl get configmap kube-proxy -n kube-system -o yaml | \
sed -e "s/strictARP: false/strictARP: true/" | \
kubectl diff -f - -n kube-system

if you see something like this

then run

kubectl get configmap kube-proxy -n kube-system -o yaml | \
sed -e "s/strictARP: false/strictARP: true/" | \
kubectl apply -f - -n kube-system

Installation with Helm

helm repo add metallb https://metallb.github.io/metallb
helm install metallb metallb/metallb --create-namespace -n metallb-system

L2 configuration

create metallb-config.yaml

apiVersion: metallb.io/v1beta1
kind: IPAddressPool
metadata:
  name: default-ip-pool
  namespace: metallb-system
spec:
  addresses:
  - 192.168.186.241-192.168.186.250
---
apiVersion: metallb.io/v1beta1
kind: L2Advertisement
metadata:
  name: default
  namespace: metallb-system
spec:
  ipAddressPools:
  - default-ip-pool

run kubectl apply -f metallb-config.yaml
Note: ip range need to be inside 192.168.186.0/24 range

Check if it works

kubectl get ipaddresspools -n metallb-system
kubectl get l2advertisement -n metallb-system

Deploy nginx

run kubectl create deploy nginx --image nginx:latest

Expose nginx

using load balancer

run kubectl expose deploy nginx --port 80 --type LoadBalancer

cheulong-sear@cheulong-linux:~$ k get svc
NAME         TYPE           CLUSTER-IP      EXTERNAL-IP       PORT(S)        AGE
kubernetes   ClusterIP      10.96.0.1       <none>            443/TCP        16d
nginx        LoadBalancer   10.106.24.222   192.168.186.242   80:32454/TCP   69s
test-nginx   NodePort       10.99.173.211   <none>            80:32544/TCP   16d

go to 192.168.186.242

using Ingress Nginx

Install ingress nginx using helm

helm upgrade --install ingress-nginx ingress-nginx \
  --repo https://kubernetes.github.io/ingress-nginx \
  --namespace ingress-nginx --create-namespace

Expose ClusterIp Service

run kubectl expose deploy nginx --port 80

create manifest to route to nginx service

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: nginx-ingress
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  ingressClassName: nginx
  rules:
  - http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: nginx
            port:
              number: 8080

kubectl apply ingress.yaml

kubectl -n ingress-nginx get svc ingress-nginx-controller

NAME                       TYPE           CLUSTER-IP    EXTERNAL-IP       PORT(S)                      AGE
ingress-nginx-controller   LoadBalancer   10.97.61.44   192.168.186.241   80:31540/TCP,443:32342/TCP   16m

go to 192.168.186.242

=== Done ===

Code for this article

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Fix audio not working on Ubuntu 24.04.3 (at least in my case)

Cheulong Sear — Sun, 05 Oct 2025 16:27:10 +0000

Recently I installed a new Ubuntu, after that my wired earphones didn't work anymore, I spent a lot of time fixing it. Here is the step that I did. It might depend on the device; in my case, it is an Asus ROG Strix.

Step 1: Check if the device is detected

Run

lspci | grep -i audio

You should see something like:

00:1f.3 Audio device: Intel Corporation CM238 HD Audio Controller (rev 31)

If nothing appears, your kernel might not detect it → you may need firmware support.

If it does appear, continue.

Step 2: Check sound card listing

aplay -l

You should see something like:

If you see “no soundcards found”, try:

sudo alsa force-reload

then check again.

Step 3: Open sound settings

pavucontrol

Install if missing: sudo apt install pavucontrol

Step 4: Reload ALSA and PulseAudio

sudo alsa force-reload
systemctl --user restart pulseaudio

If you use PipeWire (Ubuntu 24.04 does):

systemctl --user restart pipewire pipewire-pulse

Step 5: Check kernel module

Make sure the driver is loaded:

lsmod | grep snd_hda_intel

If missing, try loading it:

sudo modprobe snd_hda_intel

Then confirm:

dmesg | grep snd_hda_intel

Look for errors like:

cannot find codec
# or
device initialization failed

Step 6: Fix possible model issue

Try editing ALSA config:

sudo nano /etc/modprobe.d/alsa-base.conf

Add this line at the end

options snd-hda-intel model=alc295
options snd-hda-intel model=auto
options snd-hda-intel model=dell-headset-multi

then reboot

For me, it works

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Basic Linux command (awk)

Cheulong Sear — Sat, 16 Aug 2025 11:46:00 +0000

awk pattern scanning and processing language

awk command may not be pre-installed on all Linux distributions. To install it use

# Debian/Ubuntu
sudo apt install awk

To use awk, just type awk '{command}' filename

Here I'm using movies.txt as example

cat movies.txt
----
Title   Release Year    Budget  Profit (Approx.)        Studio  Genre
Avatar  2009    $237 million    ~$2.7 billion   20th Century Fox        Sci-Fi / Action
Avengers: Endgame       2019    $356 million    ~$2.2 billion   Marvel Studios  Superhero / Action
The Dark Knight 2008    $185 million    ~$894 million   Warner Bros.    Superhero / Crime Thriller
Titanic 1997    $200 million    ~$2.1 billion   20th Century Fox        Romance / Drama
Jurassic World  2015    $150 million    ~$1.3 billion   Universal Pictures      Sci-Fi / Adventure

Print all lines

Search Lines with a Keyword

Print Specific Columns

By default, awk uses space as separator, here I use tab as separator, so I need to set it as the separator.

Use of NR built-in variables to display line number

Use of NR built-in variables to display line 2 to 4

Use of NF built-in variables to display last field)

Print nonempty line with line number, first, second and last columns separated by `-`

Leave a comment if you have any questions.

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Basic Linux command (sed)

Cheulong Sear — Tue, 05 Aug 2025 14:56:00 +0000

sed command is stream editor for filtering and transforming text.

cheulong@master-node:~$ cat hawaii-pizza.txt
Ingredients:
1. Flour
2. Mozzarella
3. Cheese
4. Ham
5. Pizza sauce
6. Pineapple Pineapple

Let replace pineapple from the list

# file doesn't change, only output
sed 's/Pineapple/Feta/' hawaii-pizza.txt

---
Ingredients:
1. Flour
2. Mozzarella
3. Cheese
4. Ham
5. Pizza sauce
6. Feta Pineapple

By default, the sed command replaces the first occurrence of the pattern in each line

Replace

To replacing the nth occurrence of a pattern in a Line

sed 's/Pineapple/Feta/2' hawaii-pizza.txt

# All occurrence 
sed 's/Pineapple/Feta/g' hawaii-pizza.txt
# second occurrence to all occurrence 
sed 's/Pineapple/Feta/2g' hawaii-pizza.txt

Change in-place

# replace string
sed -i 's/Pineapple/Feta/' hawaii-pizza.txt

Replacing String on a Specific Line Number

sed '3 s/./!/' hawaii-pizza.txt

Printing Only the Replaced Lines

sed -n 's/Pineapple/Feta/' hawaii-pizza.txt

Replacing String on a Range of Lines

sed '1,3 s/./!/' hawaii-pizza.txt
# from line 2 to last
sed '2,$ s/./!/' hawaii-pizza.txt

Delete

Remove something

sed 's/Feta//' hawaii-pizza.txt
---
Ingredients:
1. Flour
2. Mozzarella
3. Cheese
4. Ham
5. Pizza sauce
6.

Delete Line

sed '2d' hawaii-pizza.txt

Delete Last Line

sed '$d' hawaii-pizza.txt

To Delete line from range x to y

sed '4,$d' hawaii-pizza.txt

Insert

Insert Text

sed '3i\Break' hawaii-pizza.txt  # Insert text before line 3
sed '3a\Break' hawaii-pizza.txt  # Insert text after line 3

Best Practices

Be sure to back up your files before applying for the changes. (especially while using -i)
Be careful before using regular expressions to avoid any unintended change.
Always test your SED command on sample file first before using it to avoid unintentional change.

Leave a comment if you have any questions.

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Basic Linux command (nano)

Cheulong Sear — Mon, 04 Aug 2025 10:43:00 +0000

nano is a small and friendly editor. It copies the look and feel of Pico, but is free software, and implements several features that Pico lacks, such as opening multiple files, scrolling per line, undo/redo, syntax coloring, line numbering, and soft-wrapping overlong lines.

nano command may not be pre-installed on all Linux distributions. To install it use

# Debian/Ubuntu
sudo apt install nano

To use nano, just type nano

ctl + o: to save
ctl + x: to exit

ctl + : to replace

ctl + j: to justify text
ctl + c: to show the location of the cursor

alt + a: set mark
alt + 6: to copy

ctl + k: to cut
ctl + u: to paste
alt + u: to undo
alt + e: to redo

ctl + d: to delete a character after cursor

nano +20 pizza.txt: open file with nano

nano -v pizza.txt: view only mode

Other useful command

ctl + r: to read file
ctl + w: to find
ctl + /: to go to line

Leave a comment if you have any questions.

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Basic Linux command (tree)

Cheulong Sear — Sat, 02 Aug 2025 00:19:00 +0000

tree command a utility used to display the contents of directories in a tree-like, hierarchical format.

tree command may not be pre-installed on all Linux distributions. To install it use

# Debian/Ubuntu
sudo apt install tree

# Display current directory
tree

# Display a specific directory
tree /path/to/directory

Use -d to show only directory

cheulong@master-node:~/parent$ tree -d
.
├── child1
├── child2
├── child3
├── child4
└── child5

Use -f to show full path prefix for each file

cheulong@master-node:~/parent$ tree -f
.
├── ./child1
│   └── ./child1/text.txt
├── ./child2
├── ./child3
├── ./child4
└── ./child5

Use -p to show permission for each file

cheulong@master-node:~/parent$ tree -p
[drwxrwxr-x]  .
├── [drwxrwxr-x]  child1
│   └── [-rw-rw-r--]  text.txt
├── [drwxrwxr-x]  child2
├── [drwxrwxr-x]  child3
├── [drwxrwxr-x]  child4
├── [drwxrwxr-x]  child5
└── [-rw-rw-r--]  file

Use -L <level to limit the display depth to a specified level.

cheulong@master-node:~/parent$ tree -L 1
.
├── child1
├── child2
├── child3
├── child4
├── child5
└── file

Use -sh to show size for each file

cheulong@master-node:~/parent$ tree -sh
[4.0K]  .
├── [4.0K]  child1
│   └── [   0]  text.txt
├── [4.0K]  child2
├── [4.0K]  child3
├── [4.0K]  child4
├── [4.0K]  child5
└── [ 225]  file

Other Option

-a: Include hidden files and directories (those starting with a dot).
-F: Append a forward slash (/) to directory names and an asterisk (*) to executable files.
--prune: Exclude empty directories from the output.
-u: Print the username (or UID) of each file.
-g: Print the group name (or GID) of each file.

Leave a comment if you have any questions.

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DEV Community: Cheulong Sear

How to set up k3s on Ubuntu server

What is k3s?

Prerequisite

Create the control plane

Create the worker node

1. Get the node token (on the control-plane node)

2. Join the worker node

Example:

Verify the worker joined

Optional copy kubeconfig to personal pc

Troubleshooting

hostname collusion

Your first gRPC API in Node.js

Convert Rest API to gRPC

Why use gRPC?

Example

Rest API

Install dependencies

Other Benefits

Drawbacks

Conclusion

Justfile make your life easier

What is Just?

Why use Just?

Installation

Example

Other Arguments

Env

Positional Arguments

End-to-End DevSecOps Project (Movies Finder)

Overview

Project: End-to-End DevSecOps Project (Movies Finder)

Tech Stack & Tools

Key Results & Achievements

How to set up Slack notifications from GitLab CI/CD using the Slack API

Create a Slack App

Add Incoming Webhooks

Store the Webhook URL in GitLab

Edit your .gitlab-ci.yaml

Setup cert-manager in local K8s cluster using nginx-ingress & Cloudflare DNS

Step:

Prerequisite:

1.Apply nginx deployment

2.Apply nginx clusterIp service

3.Install ingress-nginx

4.Setup Local domain name pointing to Load Balancer IP

5.Create the Cloudflare API token

6.Setup cert-manager

7.Enable TLS on ingress

Expose the Kubernetes Load Balancer on Bare Metal using MetalLB

Preparation

Installation with Helm

L2 configuration

Check if it works

Deploy nginx

Expose nginx

using load balancer

using Ingress Nginx

Expose ClusterIp Service

create manifest to route to nginx service

Fix audio not working on Ubuntu 24.04.3 (at least in my case)

Step 1: Check if the device is detected

Step 2: Check sound card listing

Step 3: Open sound settings

Step 4: Reload ALSA and PulseAudio

Step 5: Check kernel module

Step 6: Fix possible model issue

Basic Linux command (awk)

Print all lines

Search Lines with a Keyword

Print Specific Columns

Use of NR built-in variables to display line number

Use of NR built-in variables to display line 2 to 4

Use of NF built-in variables to display last field)

Print nonempty line with line number, first, second and last columns separated by -

Basic Linux command (sed)

Replace

Delete

Insert

What is `Just`?

Why use `Just`?

Print nonempty line with line number, first, second and last columns separated by `-`