Introduction to Docker

Complete introduction to Docker containerization platform, covering container concepts, Docker architecture, installation, and basic usage for cloud-native development.

Docker is an open-source platform that automates the deployment, scaling, and management of applications using containerization. It packages applications and their dependencies into lightweight, portable containers that run consistently across any environment.

What is Docker?

┌─────────────────────────────────────────────────────────────┐ │ DOCKER vs VIRTUAL MACHINES │ │ │ │ VIRTUAL MACHINES DOCKER CONTAINERS │ │ ┌─────┐ ┌─────┐ ┌─────┐ ┌─────┐ ┌─────┐ ┌─────┐ │ │ │App A│ │App B│ │App C│ │App A│ │App B│ │App C│ │ │ ├─────┤ ├─────┤ ├─────┤ ├─────┤ ├─────┤ ├─────┤ │ │ │Bins/│ │Bins/│ │Bins/│ │Bins/│ │Bins/│ │Bins/│ │ │ │Libs │ │Libs │ │Libs │ │Libs │ │Libs │ │Libs │ │ │ ├─────┤ ├─────┤ ├─────┤ └──┬──┘ └──┬──┘ └──┬──┘ │ │ │Guest│ │Guest│ │Guest│ │ │ │ │ │ │ OS │ │ OS │ │ OS │ ┌──┴───────┴───────┴──┐ │ │ └──┬──┘ └──┬──┘ └──┬──┘ │ Docker Engine │ │ │ ┌──┴───────┴───────┴──┐ ├────────────────────┤ │ │ │ Hypervisor │ │ Host OS │ │ │ ├──────────────────────┤ ├────────────────────┤ │ │ │ Host OS │ │ Hardware │ │ │ ├──────────────────────┤ └────────────────────┘ │ │ │ Hardware │ │ │ └──────────────────────┘ Lightweight (MBs) │ │ Heavy (GBs per VM) Starts in seconds │ └─────────────────────────────────────────────────────────────┘

Docker Architecture

┌─────────────────────────────────────────────────────────────┐ │ DOCKER ARCHITECTURE │ │ │ │ CLIENT DOCKER HOST │ │ ┌──────────────┐ ┌────────────────────────┐ │ │ │ docker build │ │ Docker Daemon │ │ │ │ docker pull │──REST API──►│ (dockerd) │ │ │ │ docker run │ │ │ │ │ └──────────────┘ │ ┌────────────────┐ │ │ │ │ │ Containers │ │ │ │ REGISTRY │ │ ┌──┐┌──┐┌──┐ │ │ │ │ ┌──────────────┐ │ │ │ ││ ││ │ │ │ │ │ │ Docker Hub │◄────pull────►│ │ └──┘└──┘└──┘ │ │ │ │ │ ECR / ACR │ │ └────────────────┘ │ │ │ │ GCR │ │ │ │ │ └──────────────┘ │ ┌────────────────┐ │ │ │ │ │ Images │ │ │ │ │ └────────────────┘ │ │ │ └────────────────────────┘ │ └─────────────────────────────────────────────────────────────┘

Installing Docker

bash example

# Ubuntu/Debian
sudo apt-get update
sudo apt-get install -y docker.io
sudo systemctl start docker
sudo systemctl enable docker
sudo usermod -aG docker $USER

# macOS (using Homebrew)
brew install --cask docker

# Verify installation
docker --version
docker run hello-world

Basic Docker Commands

bash example

# Run a container
docker run -d -p 80:80 --name my-web nginx

# List running containers
docker ps

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

# Stop a container
docker stop my-web

# Remove a container
docker rm my-web

# Pull an image
docker pull python:3.11-slim

# List images
docker images

# Execute command in running container
docker exec -it my-web bash

# View container logs
docker logs -f my-web

# Inspect container details
docker inspect my-web

Your First Dockerfile

Example

# Dockerfile for a Python web application FROM python:3.11-slim # Set working directory WORKDIR /app # Copy requirements and install dependencies COPY requirements.txt . RUN pip install --no-cache-dir -r requirements.txt # Copy application code COPY . . # Expose port EXPOSE 8000 # Set environment variables ENV PYTHONUNBUFFERED=1 # Run the application CMD ["python", "app.py"]

bash example

# Build the image
docker build -t my-python-app:v1.0 .

# Run the container
docker run -d -p 8000:8000 --name app my-python-app:v1.0

# Tag and push to registry
docker tag my-python-app:v1.0 myregistry.com/my-python-app:v1.0
docker push myregistry.com/my-python-app:v1.0

Why Docker Matters for Cloud Computing

Benefit	Description
Portability	Run anywhere — laptop, server, cloud
Consistency	Same environment in dev, staging, production
Isolation	Processes don't interfere with each other
Efficiency	Share OS kernel, use less resources than VMs
Speed	Start containers in seconds, not minutes
Microservices	Each service in its own container
CI/CD	Build once, deploy anywhere

Interview Questions

What is Docker and how does it differ from virtual machines?

Docker is a containerization platform that packages applications with their dependencies. Unlike VMs, containers share the host OS kernel, making them lightweight (MBs vs GBs), fast to start (seconds vs minutes), and more efficient in resource usage.

Explain the Docker architecture components.

Docker Client (CLI), Docker Daemon (manages containers/images), Docker Images (read-only templates), Containers (running instances of images), and Registry (stores images like Docker Hub). The client communicates with the daemon via REST API.

What problem does Docker solve in software development?

The "it works on my machine" problem. Docker ensures identical environments from development to production by packaging the application with all its dependencies, eliminating environment-specific bugs and simplifying deployment.

What is a Docker image and how does it relate to a container?

An image is a read-only template containing the application code, runtime, libraries, and configuration. A container is a running instance of an image — you can run multiple containers from the same image, each isolated from the others.

How does Docker improve cloud deployments?

Docker enables consistent deployments across any cloud provider, supports microservices architecture, integrates with orchestrators (Kubernetes) for scaling, reduces resource costs through efficient sharing, and accelerates CI/CD pipelines.

What is Docker?

Docker Architecture

Installing Docker

bash example

# Ubuntu/Debian
sudo apt-get update
sudo apt-get install -y docker.io
sudo systemctl start docker
sudo systemctl enable docker
sudo usermod -aG docker $USER

# macOS (using Homebrew)
brew install --cask docker

# Verify installation
docker --version
docker run hello-world

Basic Docker Commands

bash example

# Run a container
docker run -d -p 80:80 --name my-web nginx

# List running containers
docker ps

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

# Stop a container
docker stop my-web

# Remove a container
docker rm my-web

# Pull an image
docker pull python:3.11-slim

# List images
docker images

# Execute command in running container
docker exec -it my-web bash

# View container logs
docker logs -f my-web

# Inspect container details
docker inspect my-web

Your First Dockerfile

Example

bash example

# Build the image
docker build -t my-python-app:v1.0 .

# Run the container
docker run -d -p 8000:8000 --name app my-python-app:v1.0

# Tag and push to registry
docker tag my-python-app:v1.0 myregistry.com/my-python-app:v1.0
docker push myregistry.com/my-python-app:v1.0

Why Docker Matters for Cloud Computing

Benefit	Description
Portability	Run anywhere — laptop, server, cloud
Consistency	Same environment in dev, staging, production
Isolation	Processes don't interfere with each other
Efficiency	Share OS kernel, use less resources than VMs
Speed	Start containers in seconds, not minutes
Microservices	Each service in its own container
CI/CD	Build once, deploy anywhere

Interview Questions

What is Docker and how does it differ from virtual machines?

Explain the Docker architecture components.

What problem does Docker solve in software development?

What is a Docker image and how does it relate to a container?

How does Docker improve cloud deployments?

Introduction to Docker

What is Docker?

Docker Architecture

Installing Docker

Basic Docker Commands

Your First Dockerfile

Why Docker Matters for Cloud Computing

Interview Questions

Continue learning this concept

Introduction to Docker

What is Docker?

Docker Architecture

Installing Docker

Basic Docker Commands

Your First Dockerfile

Why Docker Matters for Cloud Computing

Interview Questions

Continue learning this concept