November 4, 2025 Ali TabeshPour

Getting Started with Docker

Docker has revolutionized the way we develop, ship, and run applications. In this post, I'll walk you through the basics of Docker and how to get started.

What is Docker?

Docker is a platform that enables developers to package applications into containers—standardized executable components combining application source code with the operating system (OS) libraries and dependencies required to run that code in any environment.

Why Use Docker?

Consistency: Docker ensures your application works the same way in development, testing, and production
Isolation: Each container runs in isolation, preventing conflicts between applications
Portability: Containers can run on any system that supports Docker
Efficiency: Containers share the host OS kernel, making them lighter than virtual machines

Installing Docker

On macOS

# Download Docker Desktop from docker.com
# Or use Homebrew:
brew install --cask docker

On Linux

# Update package index
sudo apt-get update

# Install Docker
sudo apt-get install docker-ce docker-ce-cli containerd.io

# Start Docker
sudo systemctl start docker

Your First Docker Container

Let's run a simple container:

docker run hello-world

This command downloads a test image and runs it in a container. When the container runs, it prints a message and exits.

Basic Docker Commands

Here are some essential Docker commands:

# List running containers
docker ps

# List all containers (including stopped)
docker ps -a

# List images
docker images

# Stop a container
docker stop <container-id>

# Remove a container
docker rm <container-id>

# Remove an image
docker rmi <image-id>

Creating a Dockerfile

A Dockerfile is a text file that contains instructions for building a Docker image. Here's a simple example for a Node.js application:

# Use official Node.js runtime as base image
FROM node:18-alpine

# Set working directory
WORKDIR /app

# Copy package files
COPY package*.json ./

# Install dependencies
RUN npm install

# Copy application files
COPY . .

# Expose port
EXPOSE 3000

# Start the application
CMD ["node", "index.js"]

Building and Running Your Image

# Build the image
docker build -t my-app .

# Run the container
docker run -p 3000:3000 my-app

Docker Compose

For multi-container applications, Docker Compose is incredibly useful:

version: '3.8'

services:
  web:
    build: .
    ports:
      - "3000:3000"
    volumes:
      - .:/app
    environment:
      - NODE_ENV=development
  
  db:
    image: postgres:15
    environment:
      - POSTGRES_PASSWORD=example
    volumes:
      - postgres-data:/var/lib/postgresql/data

volumes:
  postgres-data:

Run with:

docker-compose up

Best Practices

Use official base images when possible
Keep images small by using alpine variants
Use .dockerignore to exclude unnecessary files
Don't run containers as root when possible
Use multi-stage builds to reduce final image size
Pin versions of base images for reproducibility

Conclusion

Docker is an essential tool in modern development workflows. It simplifies deployment, ensures consistency across environments, and makes it easier to manage dependencies. Start small, experiment with containers, and gradually incorporate Docker into your development process.

Happy containerizing! 🐳