Introduction to Docker

Introduction to Docker – Why It Matters

What is Docker?

Docker is an open-source platform that allows you to package applications and their dependencies into lightweight, portable containers.

🔹 Traditional Deployment Problem

  • Works on my machine 

  • Dependency conflicts

  • Environment mismatch

🔹 Docker Solution

  • Consistent environments

  • Easy setup

  • Isolated applications

What is a Container?

A container is:

  • Lightweight

  • Portable

  • Isolated runtime environment

  • Faster than virtual machines

Docker vs Virtual Machines

FeatureDocker                        Virtual Machine
Size            MBs                        GBs
Boot Time            Seconds                        Minutes
OS Required            Shares Host OS                        Full OS required

Installing Docker & Running First Container

Step 1: Install Docker

Download from official website:

(Available for Windows, macOS, Linux)

Step 2: Verify Installation

docker --version

Step 3: Run Your First Container

docker run hello-world

This command:

  • Pulls image from Docker Hub

  • Creates container

  • Runs it

  • Displays success message

Understanding Docker Images & Containers

What is a Docker Image?

An image is a blueprint for a container.

Example:

docker pull python:3.12

What is a Container?

A running instance of an image.

docker run -it python:3.12

Useful Commands

docker images
docker ps
docker ps -a
docker stop <container_id>
docker rm <container_id>

Writing Your First Dockerfile (Python App)
Let’s Dockerize a simple Python app.
Project Structure
myapp/
 ├── app.py
 ├── requirements.txt
 └── Dockerfile
Example: app.py
print("Hello from Dockerized Python App!")
Dockerfile
FROM python:3.12

WORKDIR /app

COPY requirements.txt .
RUN pip install -r requirements.txt

COPY . .

CMD ["python", "app.py"]
Build Image
docker build -t my-python-app .
Run Container
docker run my-python-app
Dockerizing a Django Application
Since you're working heavily with Django, this is important.
Example Django Dockerfile
FROM python:3.12

ENV PYTHONDONTWRITEBYTECODE=1
ENV PYTHONUNBUFFERED=1

WORKDIR /code

COPY requirements.txt .
RUN pip install -r requirements.txt

COPY . .

CMD ["gunicorn", "project.wsgi:application", "--bind", "0.0.0.0:8000"]
Why Use Gunicorn?
Gunicorn is a production-ready WSGI server for Python apps.

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