Week 4 - Day 1: Container Basics

📚 Learning Objectives

Understand what containerization is and why it matters
Compare containers vs virtual machines
Install Docker on your system
Run your first container
Understand Docker architecture

📖 Core Concepts (2 Hours)

What is Containerization?

Containers package an application with all its dependencies into a standardized unit. "It works on my machine" becomes "It works everywhere."

Isolation: Each container runs in its own environment
Portability: Run the same container anywhere
Lightweight: Share host OS kernel, no full OS needed
Consistency: Same behavior in dev, test, and production

Containers vs Virtual Machines

                    
Virtual Machines:              Containers:
┌─────────────────┐           ┌─────────────────┐
│   App A │ App B │           │   App A │ App B │
├─────────┼───────┤           ├─────────┼───────┤
│  Guest  │ Guest │           │ Runtime │Runtime│
│   OS    │  OS   │           ├─────────┴───────┤
├─────────┴───────┤           │  Container Engine│
│   Hypervisor    │           ├─────────────────┤
├─────────────────┤           │    Host OS      │
│    Host OS      │           ├─────────────────┤
├─────────────────┤           │   Hardware      │
│   Hardware      │           └─────────────────┘
└─────────────────┘

VMs: Heavy (GBs), Slow startup, Full OS per VM
Containers: Light (MBs), Fast startup, Share kernel
                    
                

Installing Docker

                    
# Ubuntu/Debian
sudo apt update
sudo apt install -y docker.io

# Add user to docker group (avoid sudo)
sudo usermod -aG docker $USER
newgrp docker

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

# Start Docker service
sudo systemctl start docker
sudo systemctl enable docker
                    
                

Docker Architecture

                    
Docker Components:
- Docker Client: CLI commands (docker run, build, etc.)
- Docker Daemon: Background service managing containers
- Docker Registry: Storage for images (Docker Hub)
- Docker Image: Template for containers (read-only)
- Docker Container: Running instance of an image
                    
                

Basic Docker Commands

                    
# Run a container
docker run hello-world
docker run -it ubuntu bash      # Interactive terminal
docker run -d nginx             # Detached (background)
docker run -p 8080:80 nginx     # Port mapping

# List containers
docker ps                       # Running containers
docker ps -a                    # All containers

# Stop/Remove containers
docker stop container_id
docker rm container_id
docker rm -f container_id       # Force remove running

# Pull images
docker pull nginx
docker pull python:3.9

# List images
docker images
                    
                

🔬 Hands-on Lab (2.5 Hours)

Lab 1: First Containers

Run hello-world container
Run interactive Ubuntu container
Explore container file system

                    
# Lab 1: Getting started
docker run hello-world

# Interactive Ubuntu
docker run -it ubuntu bash
# Inside container:
cat /etc/os-release
ls /
exit

# Run nginx web server
docker run -d -p 8080:80 --name my-nginx nginx
curl http://localhost:8080
docker stop my-nginx
docker rm my-nginx
                    
                

Lab 2: Container Lifecycle

Create, start, stop, restart containers
View container logs
Execute commands in running containers

                    
# Lab 2: Container management
docker run -d --name web nginx
docker ps
docker logs web
docker exec -it web bash
# Inside: nginx -v && exit
docker stop web
docker start web
docker restart web
docker rm -f web
                    
                

✅ Day 1 Checklist

Understand containers vs VMs
Docker installed and working
Can run containers (docker run)
Can manage containers (ps, stop, rm)
Understand Docker architecture