Docker Compose Basics¶

Docker Compose runs multi-container applications from a YAML file. In course labs, Compose is useful for starting a web app, database, and supporting services with one command.

Goal

Confirm the Docker Compose plugin is available, then run a small web server from a compose.yaml file.

1. Prerequisite¶

Complete Docker Setup on Ubuntu Server first.

Check Docker:

docker --version
docker compose version

If docker compose version fails, install the Compose plugin:

sudo apt update
sudo apt install -y docker-compose-plugin

2. Create a Compose Lab Folder¶

mkdir -p ~/course-work/compose-test
cd ~/course-work/compose-test

3. Create `compose.yaml`¶

nano compose.yaml

Paste:

services:
  web:
    image: nginx:alpine
    ports:
      - "8080:80"

4. Start the Service¶

docker compose up -d

Check status:

docker compose ps

Test locally on the server:

curl http://localhost:8080

Expected: HTML from the Nginx welcome page.

5. Stop and Clean Up¶

docker compose down

Confirm no Compose containers remain:

docker ps

6. Common Compose Commands¶

Task	Command
Start services in foreground	`docker compose up`
Start services in background	`docker compose up -d`
Stop and remove services	`docker compose down`
View logs	`docker compose logs`
Follow logs	`docker compose logs -f`
Show service status	`docker compose ps`
Rebuild images	`docker compose build`

7. Classroom Checkpoint¶

Record:

docker compose version
docker compose ps
curl -I http://localhost:8080

Troubleshooting¶

Problem	Fix
`docker: permission denied`	Use `sudo` or complete the Docker group step from the Docker setup page.
Port 8080 already in use	Change `8080:80` to another host port, such as `8081:80`.
YAML parsing error	Check indentation. YAML uses spaces, not tabs.

Next Step¶

You are ready to run containerized course labs.