DorianABDS/Docker_Guide.md

## Docker_Guide.md

      
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              Docker_Guide.md
            
          
    📦 Docker Guide


A comprehensive practical guide to Docker, from basic commands to advanced deployments, with concrete examples and detailed explanations.


📋 Table of Contents


🟢 Beginner Level
🟡 Intermediate Level
🔴 Advanced Level
⚡ Quick Reference
🛠️ Practical Examples


🟢 Beginner Level

Installation and Basic Concepts


docker --version - Check Installation
# Check installed Docker version
docker --version

# Check detailed info
docker info
💡 Tip: Make sure Docker Desktop (Windows/Mac) or Docker Engine (Linux) is installed and running.


docker run - Run a Container
# Run an Ubuntu container and open an interactive shell
docker run -it ubuntu bash

# Run an Nginx server on port 8080
docker run -d -p 8080:80 nginx
💡 Tip: Use -d for detached mode, -p to map ports.


docker ps - List Containers
# Running containers
docker ps

# All containers (including stopped)
docker ps -a
💡 Tip: Combine with --format to customize output.


docker stop / start / rm - Manage Containers
# Stop a container
docker stop my_container

# Start a container
docker start my_container

# Remove a container
docker rm my_container
⚠️ Warning: Removing a container deletes its data unless volumes are used.


docker images - Manage Images
# List local images
docker images

# Remove an image
docker rmi nginx

# Pull an image from Docker Hub
docker pull postgres:15
💡 Tip: Always use tags (nginx:1.25) instead of latest for stability.


🟡 Intermediate Level

Building and Persisting Data


Dockerfile - Build Custom Images
# Example Node.js app
FROM node:18-alpine
WORKDIR /app
COPY package*.json ./
RUN npm install
COPY . .
EXPOSE 3000
CMD ["npm", "start"]
# Build image
docker build -t my-node-app .

# Run container
docker run -d -p 3000:3000 my-node-app
💡 Tip: Use .dockerignore to exclude unnecessary files.


Volumes - Persist Data
# Create and mount a volume
docker volume create db_data
docker run -d -v db_data:/var/lib/postgresql/data postgres:15

# Bind mount local folder
docker run -d -v $(pwd)/data:/app/data my-node-app
💡 Tip: Volumes survive container deletion, bind mounts sync with local files.


Networks - Connect Containers
# Create a custom network
docker network create my_network

# Run containers on same network
docker run -d --name db --network my_network postgres

docker run -d --name api --network my_network my-node-app
💡 Tip: Containers on the same custom network can reach each other by name.


docker-compose - Multi-Container Apps
version: '3.9'
services:
  db:
    image: postgres:15
    volumes:
      - db_data:/var/lib/postgresql/data
    environment:
      POSTGRES_PASSWORD: example
  web:
    build: .
    ports:
      - "3000:3000"
    depends_on:
      - db
volumes:
  db_data:
# Start app
docker-compose up -d

# Stop app
docker-compose down
💡 Tip: Use .env file to store secrets and environment variables.


🔴 Advanced Level

Optimization and Orchestration


Multi-stage Builds - Optimize Images
# Build stage
FROM golang:1.21 AS builder
WORKDIR /app
COPY . .
RUN go build -o myapp

# Final image
FROM alpine:3.18
COPY --from=builder /app/myapp /usr/local/bin/myapp
CMD ["myapp"]
💡 Tip: Multi-stage builds reduce image size and improve security.


docker login / push - Push to Registry
# Login to Docker Hub
docker login

# Tag and push image
docker tag my-node-app myuser/my-node-app:1.0
docker push myuser/my-node-app:1.0
💡 Tip: Use private registries for enterprise projects.


Docker Swarm - Orchestration Basics
# Init swarm
docker swarm init

# Deploy a service
docker service create --name web -p 80:80 nginx

# Scale service
docker service scale web=3
💡 Tip: Use Kubernetes for advanced orchestration at scale.


Security Best Practices

Run containers as non-root (USER in Dockerfile).
Use slim base images (alpine, distroless).
Regularly scan images (docker scan).
Keep secrets outside images (use env vars, secret managers).
Limit container privileges with --cap-drop.


⚡ Quick Reference

Common Commands

# Container lifecycle
docker run -it image bash
docker ps -a
docker stop <id>
docker rm <id>

# Images
docker images
docker pull nginx:1.25
docker rmi <id>

# Volumes & Networks
docker volume ls
docker network ls

# Compose
docker-compose up -d
docker-compose down
Dockerfile Instructions

FROM   # Base image
RUN    # Execute commands
COPY   # Copy files
WORKDIR # Set working directory
EXPOSE # Expose port
CMD    # Default command
ENTRYPOINT # Main entrypoint

🛠️ Practical Examples

Example 1: Static Website with Nginx

docker run -d -p 8080:80 -v $(pwd)/site:/usr/share/nginx/html nginx
Example 2: Node.js + PostgreSQL with docker-compose

version: '3.9'
services:
  db:
    image: postgres:15
    environment:
      POSTGRES_PASSWORD: secret
    volumes:
      - db_data:/var/lib/postgresql/data

  app:
    build: ./app
    ports:
      - "3000:3000"
    environment:
      DATABASE_URL: postgres://postgres:secret@db:5432/postgres
    depends_on:
      - db

volumes:
  db_data:
docker-compose up -d
Example 3: Multi-Stage Build for React App

# Build stage
FROM node:18-alpine AS build
WORKDIR /app
COPY . .
RUN npm install && npm run build

# Serve stage
FROM nginx:alpine
COPY --from=build /app/build /usr/share/nginx/html
EXPOSE 80
CMD ["nginx", "-g", "daemon off;"]

📖 Additional Resources


📚 Docker Documentation
📚 Dockerfile Best Practices
📚 Compose File Reference
🎮 Play with Docker
📝 Docker Cheatsheet


"This guide accompanies you in your Docker journey. From beginner to expert, each command is a step towards mastering containerization!"
✨ Created with passion by DorianABDS
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