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🎯 What is S2I?

S2I = Source-to-Image

✅ It’s a build process invented by OpenShift (Red Hat) to automate:

“Take my source code + take a base image → and build a new runnable application container.”

You give it:

• Source code (like HTML, PHP, Python app, Java code)
• S2I base image (like nginx, nodejs, python builder image)

It gives you:

• New container image that has both the code + runtime server inside.

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📦 What is an S2I Base Image?

An S2I base image is a special Docker container image that:

Feature	Description
Has a web server, app server, or runtime pre-installed	e.g., nginx, nodejs, python
Has scripts inside (assemble, run)	Helps OpenShift build a new app image automatically
Waits for your source code	Your app code is injected during build
Produces a new runnable image	Combining base + your code

✅ S2I base images are made specially for OpenShift pipelines.

They are not meant to be directly run without building first.

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🧠 Easy Example:

Imagine you want to deploy a static website:

Traditional Way	S2I Way
You manually build Docker image (nginx + your site files)	You push your HTML files to GitHub
You write Dockerfile yourself	OpenShift runs oc new-app nginx-s2i~your-git-repo
You manually build/push container	OpenShift builds everything automatically

✅ Less work for you ✅ More automation for you

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📢 Example of S2I base images:

Base Image	Language/Runtime	Usage
registry.redhat.io/rhscl/nginx-116-rhel7	nginx	Serve HTML sites
registry.redhat.io/rhscl/nodejs-14-rhel7	Node.js 14	Node.js apps
registry.redhat.io/rhscl/python-38-rhel7	Python 3.8	Python apps
registry.redhat.io/rhscl/php-73-rhel7	PHP 7.3	PHP apps

All these are S2I base images.

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📋 How an S2I base image actually works inside:

It includes scripts like:

Script	Purpose
assemble	How to copy your source code into the container and prepare the app
run	How to start the server when container runs
save-artifacts	Optional, to cache dependencies

✅ OpenShift uses these scripts automatically when you run oc new-app.

You don’t have to write Dockerfiles manually!

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🚀 S2I Full Flow (Visual)

Your GitHub Repo (HTML / PHP / Python App)
          ↓
+-------------------+
|  S2I Base Image    |
| (nginx, python)    |
+-------------------+
          ↓
OpenShift S2I Process (BuildConfig)
          ↓
New Image (runtime + your code together)
          ↓
Pod runs your application!

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🔥 When to use S2I

Use S2I if…	Reason
You have app source code (HTML, PHP, Node.js, Python, etc.)	Easy auto-build
You don’t want to write Dockerfiles manually	Saves your time
You want to build and deploy faster inside OpenShift	Automated pipelines

✅ S2I is powerful especially for development workflows and CI/CD pipelines.

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✨ In one simple sentence:

S2I Base Image is a starting point container that expects your source code and creates a ready-to-run application image automatically inside OpenShift.

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🛠 Summary Table:

Term	Meaning
S2I	Source-to-Image build process
S2I Base Image	Pre-built image waiting for your code
Used for	Automating app builds inside OpenShift
Needs Source Code?	✅ Yes
Runs directly as pod?	❌ No, needs build step first

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🚀 Practical Tip for You

Scenario	What to use
Want to run simple nginx server quickly	Use nginxinc/nginx-unprivileged
Want to build HTML app and serve	Use rhscl/nginx-116-rhel7 as S2I

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🎯 Running an S2I Base Image in OpenShift Cluster

✅ Beginner-friendly
✅ Realistic example
✅ Works on OpenShift 4.x or later

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📦 S2I Tutorial Overview

We will:

Step	Task	Description
1	Pick an S2I base image	Example: registry.redhat.io/rhscl/nginx-116-rhel7
2	Prepare simple source code	HTML project on GitHub
3	Create S2I app in OpenShift	Using oc new-app
4	Deploy and access app	Via OpenShift Route

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🛠 Step 1: Pick an S2I Base Image

We will use:

registry.redhat.io/rhscl/nginx-116-rhel7

✅ It’s an NGINX S2I builder (for serving static websites).

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🧰 Step 2: Prepare Source Code (GitHub)

You need a GitHub repo with static website files (HTML/CSS).

Example ready-to-use repo:
➡️ https://github.com/sclorg/nginx-container/tree/master/1.16/test/test-app/

Or you can create your own repo like this:

1. Create a new GitHub repo:
   Example: https://github.com/yourusername/my-s2i-nginx-app
2. Add some simple index.html:

<!-- index.html -->
<html>
  <head><title>Welcome to S2I NGINX App</title></head>
  <body><h1>Hello from OpenShift + S2I!</h1></body>
</html>

✅ Push this file to GitHub.

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🚀 Step 3: Create S2I App in OpenShift

👉 Login to your OpenShift cluster:

oc login https://your-openshift-cluster:6443

👉 Now create your S2I app:

oc new-app registry.redhat.io/rhscl/nginx-116-rhel7~https://github.com/yourusername/my-s2i-nginx-app --strategy=source

✅ What this command does:

• Pulls base image nginx-116-rhel7
• Pulls your source code from GitHub
• Builds a new image combining both
• Deploys a pod automatically

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🌍 Step 4: Expose Route (to Access App)

Create a Route:

oc expose svc/my-s2i-nginx-app

✅ Then get the URL:

oc get routes

You’ll get something like:

http://my-s2i-nginx-app-yourproject.apps.cluster.example.com

Open it in browser —
✨ You will see your HTML page served from the new OpenShift app!

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📋 Full Commands Summary

# Login
oc login https://your-openshift-cluster:6443

# Create S2I app
oc new-app registry.redhat.io/rhscl/nginx-116-rhel7~https://github.com/yourusername/my-s2i-nginx-app --strategy=source

# (Optional) Watch build
oc logs -f bc/my-s2i-nginx-app

# Expose a Route
oc expose svc/my-s2i-nginx-app

# Get public URL
oc get routes

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🔥 Important Tips

Problem	Solution
error: cannot find source repository	Check GitHub URL is public
imagepullbackoff	Check cluster can pull Red Hat registry images (pull secret)
App not updating?	Run oc start-build my-s2i-nginx-app --from-dir=. to rebuild manually

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🧠 Visual Flow

GitHub Repo (HTML)
        ↓
oc new-app (S2I build)
        ↓
BuildConfig + ImageStream created
        ↓
Pod created from new image
        ↓
Service + Route exposed
        ↓
Your app live on internet! 🚀

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🏆 Final Quick Recap

Step	Action
1	Pick S2I builder (registry.redhat.io/rhscl/nginx-116-rhel7)
2	Prepare GitHub repo (index.html)
3	Run oc new-app with --strategy=source
4	Expose service using Route

✅ You now know how to run S2I base images in OpenShift!
✅ This knowledge is essential for DevOps, OpenShift developers, CI/CD engineers.

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Let’s do a real complete project:
You’ll build your own HTML website,
then deploy it into OpenShift using S2I process.

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🎯 Project Goal

Step	Action
1	Create a simple HTML website
2	Push the website to GitHub
3	Deploy it into OpenShift using S2I base image
4	Access your site via OpenShift Route

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🛠 Step 1: Create Your Own HTML Website

On your local machine, create a project:

mkdir my-openshift-website
cd my-openshift-website

Now create a simple index.html:

<!-- my-openshift-website/index.html -->
<html>
<head>
    <title>Welcome to My OpenShift Website</title>
</head>
<body>
    <h1>Hello World from Rajesh! 🚀</h1>
    <p>Running on OpenShift with S2I magic!</p>
</body>
</html>

✅ Done — your website is ready.

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🌍 Step 2: Push Your Website to GitHub

Initialize Git and push:

git init
git add .
git commit -m "Initial commit - my openshift html site"
git branch -M main
git remote add origin https://github.com/yourusername/my-openshift-website.git
git push -u origin main

✅ Now your project is live at:

https://github.com/yourusername/my-openshift-website

(Public GitHub repo needed for OpenShift to pull.)

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🚀 Step 3: Deploy to OpenShift Using S2I

✅ Login to your OpenShift cluster:

oc login https://your-openshift-cluster:6443

✅ Now run S2I Deployment:

oc new-app registry.redhat.io/rhscl/nginx-116-rhel7~https://github.com/yourusername/my-openshift-website --strategy=source

✅ OpenShift will:

• Pull NGINX S2I base image (rhscl/nginx-116-rhel7)
• Pull your HTML website from GitHub
• Build a new container image
• Deploy a Pod automatically

✅ Watch the build logs (optional):

oc logs -f bc/my-openshift-website

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🌐 Step 4: Expose your app with a Route

✅ Create a Route:

oc expose svc/my-openshift-website

✅ Get the public URL:

oc get routes

You’ll get something like:

http://my-openshift-website-myproject.apps.cluster.example.com

✅ Open this URL in browser!

🎉 You’ll see:

Hello World from Rajesh! 🚀
Running on OpenShift with S2I magic!

✅ Your custom HTML website is now live on OpenShift! 🌟

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📋 Full Commands Summary (Cheat Sheet)

# 1. Create HTML site
mkdir my-openshift-website && cd my-openshift-website
# (create index.html)

# 2. Push to GitHub
git init
git add .
git commit -m "initial commit"
git remote add origin https://github.com/yourusername/my-openshift-website.git
git push -u origin main

# 3. Deploy to OpenShift
oc login https://your-openshift-cluster:6443
oc new-app registry.redhat.io/rhscl/nginx-116-rhel7~https://github.com/yourusername/my-openshift-website --strategy=source

# 4. Watch build (optional)
oc logs -f bc/my-openshift-website

# 5. Expose
oc expose svc/my-openshift-website

# 6. Get URL
oc get routes

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🧠 Visual Architecture

Your GitHub Repo (index.html)
         ↓
S2I Build Process (oc new-app)
         ↓
BuildConfig + ImageStream
         ↓
New Container Image Created
         ↓
Pod Running + Service
         ↓
Route Created
         ↓
Public Website LIVE 🚀

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📢 Key Points to Remember

Topic	Tip
Base Image	registry.redhat.io/rhscl/nginx-116-rhel7
Strategy	--strategy=source
Code Location	Public GitHub repo
Exposing service	Use oc expose svc/<service-name>
Cluster pull secrets	Must be able to pull Red Hat registry images

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🏆 Now you know how to:

✅ Create your own HTML app
✅ Deploy it into OpenShift using S2I
✅ Access it publicly over internet
✅ Automate build from GitHub source
✅ Master basic OpenShift developer workflow 🚀

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