version: 1
id: docker-volumes
title: Persist Data with Volumes
summary: Fix a Compose file so application data survives container restarts using named volumes.
difficulty: intermediate
estimatedMinutes: 30
prerequisites: [docker-networking]
image: alpine:3.21
shell: /bin/sh
setup:
  - "printf 'services:\\n  api:\\n    image: nginx:alpine\\n    ports:\\n      - \"8080:80\"\\n' > /workspace/compose.yaml"
tasks:
  - id: volume-persist
    title: Add durable storage
    description: Update compose.yaml to mount a named volume at /usr/share/nginx/html for the api service and declare the volume at the top level.
    hints:
      - volumes can be defined under services.api.volumes and in the top-level volumes block.
      - Use a named volume like webdata.
    checks:
      - type: file
        name: Named volume declared
        path: /workspace/compose.yaml
        value: webdata
      - type: command
        name: Mount path configured
        command: grep -q '/usr/share/nginx/html' /workspace/compose.yaml
      - type: command
        name: Service still defined
        command: "grep -q 'image: nginx' /workspace/compose.yaml"
limits: {cpus: "0.5", memory: 128m, pids: 64, timeout: 1800, network: false}