Compose = declarative multi-container orchestration on one host

It expands into many Docker API calls.

Core Concepts

Project: everything in one compose file
Service: container definition
Container: runtime instance
Desired state: what should be running

File Structure

services:   
	app:     
		image / build     
		ports     
		volumes     
		environment     
		depends_on  
networks: 
volumes:

Key Mappings

Compose	Docker equivalent
`services`	`docker run`
`build`	`docker build`
`image`	`docker pull`
`ports`	`-p`
`volumes`	`-v / --mount`
`environment`	`-e`
`networks`	`docker network create`
`restart`	restart policy
`command`	override `CMD`
`entrypoint`	override `ENTRYPOINT`

Networking (Compose Magic)

Auto bridge network
Service name = DNS hostname
No manual IPs
Isolated per project

Lifecycle Commands

docker compose up 
docker compose down 
docker compose restart 
docker compose ps 
docker compose logs 
docker compose exec

What Compose Does NOT Do

No health-based readiness
No auto-scaling
No scheduling
No self-healing

When to Use

Single container → Docker
Multiple cooperating containers → Compose
Distributed / scaled system → Kubernetes

See Also