Lesson 2.1: Docker Concepts

What is Docker?

Docker is a containerization platform that packages applications and their dependencies into lightweight, portable containers.

Key Concepts

Images vs Containers

• Image: Read-only template (like a blueprint)
• Container: Running instance of an image

Dockerfile

Text file with instructions to build an image:

FROM nginx:alpine
COPY ./html /usr/share/nginx/html
EXPOSE 80
CMD ["nginx", "-g", "daemon off;"]

Docker Registry

Repository for Docker images:

• Docker Hub: Public registry
• Private Registry: Self-hosted
• GitHub Container Registry: Integrated with GitHub

Docker Architecture

Understanding the Docker ecosystem:

• Docker Engine: Core runtime
• Docker CLI: Command-line interface
• Docker Daemon: Background service
• Docker API: REST API for automation

Essential Docker Commands

# Image Management
docker pull nginx:alpine
docker images
docker rmi nginx:alpine

# Container Management
docker run -d --name web nginx:alpine
docker ps
docker ps -a
docker stop web
docker start web
docker rm web

# Logs and Debugging
docker logs web
docker exec -it web /bin/sh
docker inspect web

Why Docker for Personal Cloud?

• Isolation: Services don not interfere with each other
• Portability: Run anywhere Docker is installed
• Consistency: Same environment across development/production
• Resource Efficiency: Lightweight compared to VMs
• Easy Updates: Pull new image versions

MCT Services Docker Strategy

Our approach to containerizing services:

• Official Images: Use official images when available
• LinuxServer.io: Community-maintained images
• Custom Images: Build when necessary
• Security: Regular image updates

Container Networking Basics

Docker networking modes:

• Bridge: Default isolated network
• Host: Use host network directly
• None: No networking
• Custom: User-defined networks

Volume Management

Persistent data strategies:

• Named Volumes: Docker-managed storage
• Bind Mounts: Host directory mapping
• tmpfs: In-memory storage

Practical Exercise

Task: Run your first containerized service

1. Install Docker on your system
2. Pull the nginx image
3. Run nginx container with port mapping
4. Access the service via browser
5. Examine logs and container details
6. Stop and remove the container