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Answer: Compose lets you define and manage multi-container apps in one YAML file. (S2) In the Compose Specification, a service is an abstract concept implemented on platforms by running the same container image, and configuration, one or more times. (S1)

Building blocks

• In the Compose Specification, a network is a platform capability abstraction to establish an IP route between containers within services connected together. (S1)
• The Specification describes persistent data as a high-level filesystem mount with global options. (S1)
• From inside the container, configs behave like volumes: they're mounted as files. (S1)

The Compose file

• The default path for a Compose file is compose.yaml (preferred) or compose.yml that is placed in the working directory. (S1)
• Compose also supports docker-compose.yaml and docker-compose.yml for backwards compatibility of earlier versions. (S1)
• If both files exist, Compose prefers the canonical compose.yaml. (S1)
• Compose offers a way for you to set a custom project name, so that the same compose.yaml file can be deployed twice on the same infrastructure by passing a distinct name. (S1)

Day-to-day benefits

• Compose caches the configuration used to create a container. When you restart a service that has not changed, Compose reuses the existing containers. (S2)
• Compose supports variables in the Compose file, which you can use to customize your composition for different environments, or different users. (S2)

Claims

• id: C1 claim: A Compose service runs the same image and configuration one or more times. source: S1 evidence: "and configuration, one or more times."
• id: C2 claim: compose.yaml is the preferred default Compose file. source: S1 evidence: "If both files exist, Compose prefers the canonical compose.yaml."
• id: C3 claim: Compose reuses existing containers for unchanged services. source: S2 evidence: "When you restart a service that has not changed, Compose reuses the existing containers."
• id: C4 claim: Compose supports variables in the Compose file. source: S2 evidence: "Compose supports variables in the Compose file."

Sources

• [S1] How Compose works. Docker Docs. https://docs.docker.com/compose/intro/compose-application-model/ . License: Docker docs, Apache-2.0 (github.com/docker/docs; https://github.com/docker/docs/blob/main/LICENSE); Docker name and logo are trademarks of Docker Inc and are not licensed. Accessed 2026-11-04.
• [S2] Why use Compose?. Docker Docs. https://docs.docker.com/compose/intro/features-uses/ . License: Docker docs, Apache-2.0 (github.com/docker/docs; https://github.com/docker/docs/blob/main/LICENSE); Docker name and logo are trademarks of Docker Inc and are not licensed. Accessed 2026-11-04.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted).

@misc{iil_note_w47j684d,
  author = {{iinventedlight}},
  title = {{Docker Compose: the application model and compose.yaml}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-04},
  url = {https://iinventedlight.com/library/notes/docker-compose-basics/},
  note = {Permanent ID iil:note:w47j684d. License: CC-BY-4.0.},
}

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