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Week 5 IconWeek 5 - Lab 2: Docker and Orchestration

Module: Operating Systems 3 (Virtualisation & Cloud Technologies)
Topic: Docker Engine, Networking, Compose, and Portainer
Estimated Time: 90 Minutes Instructor: KT Nshimba

Lab Overview

In Lab 1, you learnt about System Containers (LXC). Now, we switch to Application Containers (Docker), which are designed to package single processes.

This comprehensive lab covers the entire Docker lifecycle: 1. Fundamentals: Installing Docker and running your first container. 2. Networking: Connecting containers manually. 3. Orchestration: Using Docker Compose to define a full stack (WordPress + MySQL) as code. 4. Management: Installing Portainer to manage it all via a GUI.

Prerequisites: - The Ubuntu Server VM from Week 2 (or a fresh VM). - Internet access.

Part 1: Docker Fundamentals

We will start by interacting with the Docker Engine directly via CLI.

Step 1: Install Docker

  1. Log in to your Ubuntu VM.
  2. Install Docker and the Compose plugin: bash sudo apt update sudo apt install -y docker.io docker-compose-plugin
  3. Add your user to the docker group (optional): bash sudo usermod -aG docker $USER # Log out and back in required!

Step 2: The "Hello World" of Web Servers

  1. Run the Container: bash docker run -d --name my-web -p 8080:80 nginx

    • -d: Detached mode.
    • -p 8080:80: Forwards port 8080 on VM to port 80 in container.

  2. Verify:

    • Open your browser to http://<VM-IP>:8080.
    • You should see "Welcome to nginx!".

  3. Clean Up: bash docker rm -f my-web

Part 2: Docker Networking (The Hard Way)

  1. Create a Network: bash docker network create lab-net

  2. Launch Containers: bash docker run -d --name alpine1 --network lab-net alpine sleep 3600 docker run -d --name alpine2 --network lab-net alpine sleep 3600

  3. Test DNS Resolution: Docker allows pinging by name. bash docker exec -it alpine1 ping -c 3 alpine2

    • Result: alpine2 should resolve to an IP.

  4. Clean Up: bash docker rm -f alpine1 alpine2 docker network rm lab-net

Part 3: Orchestration with Docker Compose

Running individual commands is error-prone. Docker Compose defines infrastructure in YAML.

Step 1: Create Workspace

  1. Run the following commands: bash mkdir ~/my-wordpress cd ~/my-wordpress nano docker-compose.yaml

Step 2: Define the Stack

Paste the following configuration into the file:

version: '3.8'

services:
  db:
    image: mysql:5.7
    volumes:
      - db_data:/var/lib/mysql
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: somewordpress
      MYSQL_DATABASE: wordpress
      MYSQL_USER: wordpress
      MYSQL_PASSWORD: wordpress

  wordpress:
    depends_on:
      - db
    image: wordpress:latest
    ports:
      - "8000:80"
    restart: always
    environment:
      WORDPRESS_DB_HOST: db:3306
      WORDPRESS_DB_USER: wordpress
      WORDPRESS_DB_PASSWORD: wordpress
      WORDPRESS_DB_NAME: wordpress

volumes:
  db_data:

Step 3: Deploy

Run the stack in detached mode:

docker compose up -d

Step 4: Verify

Part 4: Management with Portainer

Step 1: Deploy Portainer

Run the following long command to launch the Portainer container:

docker run -d -p 9000:9000 -p 9443:9443 --name portainer \
  --restart=always \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -v portainer_data:/data \
  portainer/portainer-ce:latest

Step 2: Access the GUI

  1. Go to https://<VM-IP>:9443 in your browser.
  2. Accept the Self-Signed Certificate Warning.
  3. Create an admin user and password.
  4. Select Get Started.

Step 3: Explore

Lab Checkpoint

Practical Skills Checklist

Reflection

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