Multi-entrypoint: unable to use docker-compose `command` to run bash script after setup apache+bind mounts

Open Source Projects Compose
1

Issue
Unable to automate last part of a tree-step Apache server setup with docker-compose up. Steps are:

  1. Build the image (includes Apache configs) and start Apache in FOREGROUND [✓]
  2. Mount two directories (bind mounts) with images for the web app to serve [✓]
  3. Use /bin/bash entrypoint to run script that reads mounted dirs and creates file for the web app [ ]

The container exits with code 0 right after setup is completed!

System environment
Linux 4.15.0-33-generic #36-Ubuntu x86_64
Docker 18.06.1-ce, build e68fc7a
docker-compose 1.22.0, build f46880fe

Steps to reproduce
Step 1 of the setup can be configured within the Dockerfile and CMD for starting Apache.
Dockerfile:

FROM ubuntu:16.04

RUN apt-get update -y
RUN DEBIAN_FRONTEND=noninteractive apt-get -y -o Dpkg::Options::="--force-confdef" -o Dpkg::Options::="--force-confold" upgrade

RUN apt-get install -y apache2 libapache2-mod-perl2 libcgi-session-perl libapache2-mod-php make php python

...

EXPOSE 80

CMD ["/usr/sbin/apache2ctl", "-D", "FOREGROUND"]

However, the remaining steps can only be performed when spinning a container(?). I was hoping to simply run
docker-compose up and let the compose file mount the dirs and command execute the script.
Compose file:

version: '3'

services:
  server:
    build: .
    volumes:
      - ./volume/Images/:/var/www/html/LabelMeAnnotationTool/Images/:rw
      - ./volume/Annotations/:/var/www/html/LabelMeAnnotationTool/Annotations/:rw
    ports:
      - 80:80
   command: ["/bin/bash","-c","python","populate-dirlist.py"]

My guess is the ‘exit code 0’ is due to the fact that command is overwriting the entrypoint of the container and since /bin/bash is “non-blocking”, it exists right away.

My question is then: How can I make sure that python script runs after the dirs are mounted, while keeping apache running in foreground?