Definition

Docker is a containerization platform that enables developers to package applications and their dependencies into lightweight, portable containers. These containers can run consistently across different environments, from development laptops to production servers, solving the "it works on my machine" problem.

Key Concepts

Containers: Lightweight, standalone packages that include everything needed to run an application
Images: Read-only templates used to create containers
Dockerfile: Text file containing instructions to build Docker images
Registry: Storage and distribution system for Docker images (Docker Hub)
Orchestration: Managing multiple containers with tools like Docker Compose

Example Dockerfile

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

# Set working directory in container
WORKDIR /app

# Copy package.json and package-lock.json
COPY package*.json ./

# Install dependencies
RUN npm ci --only=production

# Copy application code
COPY . .

# Expose port 3000
EXPOSE 3000

# Define environment variable
ENV NODE_ENV=production

# Run the application
CMD ["npm", "start"]

Docker Commands

# Build an image from Dockerfile
docker build -t myapp:latest .

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

# List running containers
docker ps

# Stop a container
docker stop myapp-container

# Remove a container
docker rm myapp-container

# Pull an image from registry
docker pull nginx:latest

# View container logs
docker logs myapp-container

# Execute command in running container
docker exec -it myapp-container /bin/sh

Career Impact

$85K+

Average DevOps Engineer Salary

78%

Of Companies Use Containerization

25K+

Docker-Related Job Openings

Benefits of Docker

Consistency: Applications run the same across all environments
Portability: Containers run on any system that supports Docker
Efficiency: Lightweight compared to virtual machines
Scalability: Easy to scale applications horizontally
Isolation: Applications are isolated from each other
Version Control: Images can be versioned and rolled back

Docker Ecosystem

Docker Compose: Multi-container application orchestration
Docker Swarm: Native clustering and orchestration
Docker Hub: Cloud-based registry service
Docker Desktop: Development environment for Mac and Windows
Kubernetes: Advanced container orchestration platform

Learning Path

Understand containerization concepts and benefits
Install Docker and learn basic commands
Create your first Dockerfile and build images
Learn Docker networking and volumes
Master Docker Compose for multi-container apps
Explore container registries and image management
Study container orchestration with Kubernetes
Learn Docker security best practices

Docker