Support for volume file mounts in one-click-apps

[githubsaturn]

Discussed in https://github.com/caprover/caprover/discussions/2245

^{Originally posted by nktnet1 January 25, 2025} Hello,

I believe currently, there is no way to create a one-click-app template that comes with a persistent config file mounted in volume, e.g. a python file such as superset_config.py.

For context, I would like to convert the following superset template:

services:
  db: .....
  redis: .....
  superset:
    image: amancevice/superset
    restart: always
    depends_on:
      - db
      - redis
    environment:
      MAPBOX_API_KEY: ${MAPBOX_API_KEY}
    ports:
      - "8088:8088"
    volumes:
      # Ideally create this file automatically with one-click-apps
      - ./superset_config.py:/etc/superset/superset_config.py

In alternatives like Dokploy/Coolify, this is possible using

• Dokploy's mounts in index.ts
• Coolify's volume content - see docs

Would it be possible to implement something similar for Caprover?

[githubsaturn]

Thinking about this a bit more, it's actually doable through a simple hack:

services:
    $$cap_appname-delete-me-after-installation:
        volumes:
            - $$cap-some-volume-name:/mydata
        caproverExtra:
            dockerfileLines:
                - FROM alpine:latest
                - RUN mkdir /mydata
                - ENV FILE_CONTENT="line 1
                - line 2
                - line 3"
                - RUN echo $'#!/bin/sh\n\
                - echo "$FILE_CONTENT" > /mydata/myfile\n\
                - tail -f /dev/null' > /startup.sh
                - RUN chmod +x /startup.sh
                - CMD ["/startup.sh"]

This container creates a file with pre-specified content at a specific volume on start up. The only downside is that user needs to delete this container manually after installation is done.