Docker Technology Intelligence

What is Docker?

Docker is a platform for developing, shipping, and running applications in containers. Containers package applications with their dependencies, ensuring consistent behavior across development, testing, and production environments.

Created by Solomon Hykes at dotCloud in 2013, Docker revolutionized software deployment by making containers accessible to developers. Unlike virtual machines, containers share the host OS kernel, providing lightweight isolation with minimal overhead. Docker became the industry standard for containerization, enabling microservices architectures and modern DevOps practices.

Key Features

Containers

• Isolation: Process and filesystem separation
• Lightweight: Share host OS kernel
• Portable: Run anywhere Docker runs
• Fast: Start in seconds

Images

• Layers: Efficient storage and transfer
• Dockerfile: Declarative image definition
• Registry: Share images via Docker Hub
• Tags: Version management

Networking

• Bridge: Default container networking
• Host: Direct host networking
• Overlay: Multi-host networking
• Port Mapping: Expose container ports

Volumes

• Persistent data storage
• Shared data between containers
• Bind mounts to host
• Volume drivers

Use Cases

Development Environments

Teams standardize development environments with Docker. New developers start quickly without installing dependencies manually. "Works on my machine" problems disappear.

Microservices

Organizations deploy microservices in containers. Each service packages independently, scales individually, and updates without affecting others.

CI/CD Pipelines

Build pipelines use Docker for consistent build environments. Tests run in containers matching production, catching environment-specific issues early.

Local Services

Developers run databases, caches, and message queues locally. Docker Compose starts complete development stacks with one command.

Cloud Deployment

Cloud platforms run Docker containers natively. AWS ECS, Google Cloud Run, and Azure Container Instances deploy containers without managing servers.

Legacy Application Migration

Organizations containerize legacy applications. Containers provide isolation while applications modernize incrementally.

Code Examples

Dockerfile

# Node.js application
FROM node:20-alpine

WORKDIR /app

# Install dependencies first (caching)
COPY package*.json ./
RUN npm ci --only=production

# Copy application code
COPY . .

# Build application
RUN npm run build

EXPOSE 3000

CMD ["node", "dist/index.js"]

Multi-stage Build

# Build stage
FROM node:20-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

# Production stage
FROM node:20-alpine
WORKDIR /app
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/node_modules ./node_modules
EXPOSE 3000
CMD ["node", "dist/index.js"]

docker-compose.yml

version: '3.8'

services:
  app:
    build: .
    ports:
      - "3000:3000"
    environment:
      - DATABASE_URL=postgres://user:pass@db:5432/myapp
    depends_on:
      - db
      - redis

  db:
    image: postgres:15-alpine
    volumes:
      - postgres_data:/var/lib/postgresql/data
    environment:
      - POSTGRES_USER=user
      - POSTGRES_PASSWORD=pass
      - POSTGRES_DB=myapp

  redis:
    image: redis:7-alpine

volumes:
  postgres_data:

Common Commands

# Build image
docker build -t myapp:latest .

# Run container
docker run -d -p 3000:3000 --name myapp myapp:latest

# View logs
docker logs -f myapp

# Execute command in container
docker exec -it myapp sh

# Docker Compose
docker-compose up -d
docker-compose logs -f
docker-compose down

Ecosystem

Docker vs Podman

• Daemon: Docker uses daemon, Podman daemonless
• Root: Podman rootless by default
• Compatibility: Podman CLI compatible
• Adoption: Docker more widespread

Container Orchestration

• Kubernetes: Industry standard orchestration
• Docker Swarm: Built-in clustering
• Nomad: HashiCorp alternative
• ECS: AWS container service

Related Tools

• Docker Hub: Public image registry
• Docker Desktop: Local development
• Buildx: Multi-platform builds
• Docker Scout: Security scanning

Strengths

• Industry standard
• Excellent documentation
• Large image ecosystem
• Cross-platform support

Considerations

• Learning curve
• Resource overhead vs bare metal
• Security requires attention
• Desktop licensing changes