What is Docker?

What is Docker?

 Docker is a platform that lets you package your applications and all their dependencies into a single container so they run consistently across different environments.

it provide better approach to create and manage build to any platform

Think of it like this:

• Without Docker: "It works on my machine" problem happens because environments differ.

• With Docker: You send the same container image that runs exactly the same everywhere — laptop, server, or cloud.

Key points:

• Image = Blueprint/template of your app.

• Container = Running instance of that image.

• Dockerfile = Script with instructions to build an image.

• Registry – Storage for images (Docker Hub, AWS ECR, Azure ACR)

• Volume – Persistent storage for containers

• Network – Communication between containers

---

2. Install Docker on Windows

1. Check your Windows Version
   Docker Desktop works best on Windows 10/11 Pro/Enterprise (with WSL2).
   If you have Windows Home, it also works but WSL2 is required.

2. Download Docker Desktop

   • Go to Docker official site

   • Download Docker Desktop for Windows.

3. Install Docker Desktop

   • Run the installer.

   • Make sure "Use WSL 2 instead of Hyper-V" is checked (for most systems).

   • Follow prompts and restart if required.

4. Enable WSL 2 (if not already)

   • Open PowerShell (Admin) and run:

     powershell
     
     wsl --install
     

   • Restart your system.

5. Verify Docker Installation
   Open Command Prompt or PowerShell:

   bash
   
   docker --version 
   

   You should see something like:

   nginx
   
   Docker version 27.0.3, build abc123

3. Basic Docker Commands

# Get images
docker images

# Pull image from Docker Hub
docker pull nginx

# Run container
docker run -d -p 8080:80 nginx

# List running containers
docker ps

# Stop container
docker stop <container_id>

# Remove container
docker rm <container_id>

# Remove image
docker rmi nginx

---

3. Simple Example: Create & Build with Docker

We’ll create a simple Hello World Python app and run it in Docker.

Step 1 — Create a project folder

bash

mkdir docker-demo
cd docker-demo

Step 2 — Create app.py

python

# app.py
print("Hello from Docker!")

Step 3 — Create Dockerfile

dockerfile

# Use official Python image
FROM python:3.9

# Set working directory
WORKDIR /app

# Copy all files to container
COPY . /app

# Run the Python app
CMD ["python", "app.py"]

Step 4 — Build the Docker Image

bash

docker build -t my-python-app .

Here:

• -t my-python-app = Tag/name for your image.

• . = Build from current folder.

Step 5 — Run the Docker Container

bash

docker run my-python-app

You should see:

Hello from Docker!

🚀 Push Docker Image to Docker Hub (Windows Steps)
1. Open PowerShell or CMD

Make sure Docker Desktop is running (check the whale 🐳 icon in your taskbar).

2. Login to Docker Hub

Run:

docker login


It will ask:

Username: <your-dockerhub-username>
Password: <your-dockerhub-password>

👉 If you enabled 2FA on Docker Hub, you’ll need to create a Personal Access Token
 from Docker Hub and use that instead of a password.

If successful:

Login Succeeded

3. Check Your Local Images

Run:

docker images


Example output:

REPOSITORY        TAG       IMAGE ID       CREATED          SIZE
my-python-app     latest    1a2b3c4d5e6f   10 minutes ago   123MB

4. Tag the Image

You must tag your image with your Docker Hub username and repo name.

docker tag my-python-app:latest <your-dockerhub-username>/my-python-app:v1


Example (if your Docker Hub username is shivagautam):

docker tag my-python-app:latest shivagautam/my-python-app:v1

Check again:

docker images


Now you should see:

REPOSITORY                   TAG     IMAGE ID       CREATED         SIZE
shivagautam/my-python-app    v1      1a2b3c4d5e6f   10 minutes ago  123MB

5. Push the Image

Push the tagged image to Docker Hub:

docker push <your-dockerhub-username>/my-python-app:v1

Example:

docker push shivagautam/my-python-app:v1


You’ll see something like:

The push refers to repository [docker.io/shivagautam/my-python-app]
v1: Pushed
latest: digest: sha256:abc123... size: 1234

6. Verify on Docker Hub

Go to https://hub.docker.com

Click on Repositories

You’ll see my-python-app with tag v1

7. (Optional) Pull on Another Machine

You can pull and run your image anywhere:

docker pull <your-dockerhub-username>/my-python-app:v1
docker run <your-dockerhub-username>/my-python-app:v1

pull docker image into external drive
docker image
docker save -o myfirst.tar shivadockerind/my-python-app-new:v1