Top-level volumes

Declare persistent Compose storage

Lesson 15 of 20 · 12 min · Module 5: Readiness and runtime boundaries

Describe persistent storage as part of the stack contract.

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Separate declaration from attachment
Preserve the intended destination

The idea

Compose describes services and their relationships as YAML mappings and sequences. Read the whole service graph, including access and storage boundaries.

services:
  worker:
    image: notes:1.0
    volumes: ["worker-data:/data"]
volumes:
  worker-data: {}

01Separate declaration from attachment

The top-level volumes mapping declares a named volume. A service mount attaches it to the path the application uses.

02Preserve the intended destination

The application expects /data. Mounting the same volume at an unrelated path does not automatically move the application storage there.

03Plan a recovery procedure

Persistence survives routine replacement, but a restore test is still needed for data loss. The Infrastructure & Operations course practices that separate responsibility.

Your turn

Define api with image notes:1.0 and volume notes-data mounted at /data. Declare notes-data in the top-level volumes mapping.

What the checks look for

Declares the named volume
Mounts it at the application data path

Try it in the editor →

Take this with you

Make the storage contract explicit and test recovery separately.

Go a little further

Rewrite the mount using Compose long syntax.