Tool cheatsheet

Docker Compose file Cheatsheet

compose.yaml snippets for services, ports, volumes, networks, environment, health checks, profiles and development workflows.

Services

A web app with a database — Two services: an app built from a Dockerfile, and PostgreSQL with a named volume. Keep real passwords in an env file.
Use an image or build one — Pull an image, or build from a folder with build arguments.
Publish ports — Map host ports to container ports. Bind to localhost to keep a port private to your machine.
Override the command — Change the command or entrypoint that the image defines.
Restart automatically — Restart on failure, or unless you stop it manually.
Add a health check — Mark a service healthy only when a command succeeds.
Wait for a dependency to be healthy — Start a service only after another reports healthy.
Limit CPU and memory — Cap what a service can use.

Set environment variables — Set variables inline, as a list or a map.
Load variables from a file — Read variables from one or more env files. Keep them out of version control.
Use variables with defaults — Substitute values from the shell or .env, with a default or a required error.
Use secrets — Mount a secret as a file under /run/secrets rather than an environment variable.
Mount a config file — Provide a configuration file to a service.

Use a named volume — Persist data in a volume managed by Docker.
Mount a host folder — Mount source code into a container for development. :ro makes it read-only.
Use an in-memory mount — Mount temporary storage in memory.
Create separate networks — Isolate services: the proxy can reach the app, but not the database.
Join an existing network — Attach to a network created outside this file.

Make services optional — Start a service only when its profile is enabled, with docker compose --profile debug up.
Sync or rebuild on file changes — Update running containers as you edit code, with docker compose watch.
Override settings for development — compose.override.yaml is merged automatically over compose.yaml.
Include another Compose file — Reuse a service definition kept in a separate file.
Avoid repetition with anchors — Define settings once and reuse them in several services.

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