Docker Compose: A Beginner’s Guide to Multi‑Container Orchestration

In the previous articles of this series we covered Docker basics, image building, data mounting, and container networking; now we turn to Docker Compose for orchestrating multiple containers.

We use a simple example consisting of a web service and a Redis database, where the web service mounts local data for debugging and connects to Redis for data operations.

When composing, a top‑level project (by default the folder name) groups several service definitions; in the example the services are web and redis .

The docker-compose.yml file (see the illustration) starts by specifying the Compose version, then defines each service under the services key with detailed settings.

build : rebuild the image from a Dockerfile.

container_name : assign a custom container name.

image : use an existing image directly.

ports : map host ports to container ports.

networks : attach the container to a network.

depends_on : declare service dependencies to control start order.

volumes : configure data mounts, either bind‑mounts or named volumes.

restart : define restart policy.

env_file : reference a file containing environment variables.

environment : set environment variables directly.

command : specify the command to run when the container starts.

Networks defined under the top‑level networks section allow services with matching network names to communicate with each other.

The depends_on directive ensures that dependent containers (e.g., web depends on redis ) start after their prerequisites, though it only checks that the container is running; for finer control you can use tools like wait-for-it or dockerize .

Volumes can be traditional bind mounts or named volumes; named volumes must also be declared under the top‑level volumes section.

Environment variables can be set individually with environment or collectively via an env_file that is referenced in the service definition.

docker-compose up

Running the above command launches all defined containers at once; afterwards you can use other Compose commands such as pause , unpause , start , stop , restart , kill , and down for further management.

In conclusion, we have covered the full workflow from building images to orchestrating containers on a single host; future articles will explore multi‑host orchestration with Docker Swarm and Kubernetes, which are becoming the industry standard.