Add custom entrypoint

[dmuiX]

Hello,

I have read your comment on stackoverflow and the script you published here.
You write sth. about:
Proper entrypoint script can be written as almost universal way of processing secrets, because we can pass original image entrypoint as argument to our new entrypoint script so original image "decorator" is doing it's own work after we prepare container with our script.

But I don‘t see how you have implemented this directly in the entrypoint script. I can see that you are creating a new Dockerfile and do something there.
This is not what I want. I actually want to have a entrypoint script that I can use in any docker-compose file I have converts my ENV_VAR_FILE to ENV_VAR but then executes any entrypoint or cmd that is included in the image itself.
But maybe this is just possible by creating a new Dockerfile??

calibre.yml

version: '3.8'
services:
  calibre:
    image: lucapisciotta/calibre
    container_name: calibre
    user: ${PUID}:${PGID}
    entrypoint: ./entrypoint.sh
    env_file: calibre.env
    volumes:
        - /srv/mergerfs/NAS/Media/Calibre-Library:/books
    restart: unless-stopped
    networks: 
      - swag
    secrets:
      - admin_password

secrets:
  admin_password:
    file: ./admin_password

networks:
  swag:
    external: true

calibre.env

ADMIN_PASSWORD_FILE=/run/secrets/admin_password
# https://medium.com/@adrian.gheorghe.dev/using-docker-secrets-in-your-environment-variables-7a0609659aab
ENABLE_AUTH=true
TZ=Europe/Berli

entrypoint.sh (is not your script, but similiar and actually does not work…)

#!/bin/bash

set -e

file_env() {
   local var="$1"
   local fileVar="${var}_FILE"
   local def="${2:-}"

   if [ "${!var:-}" ] && [ "${!fileVar:-}" ]; then
      echo >&2 "error: both $var and $fileVar are set (but are exclusive)"
      exit 1
   fi
   local val="$def"
   if [ "${!var:-}" ]; then
      val="${!var}"
   elif [ "${!fileVar:-}" ]; then
      val="$(< "${!fileVar}")"
   fi
   export "$var"="$val"
   unset "$fileVar"
}

file_env "ADMIN_PASSWORD

[DevilaN]

You either create new image starting from old one and adding my entrypoint.sh with ADD command and then set old entrypoint to be executed with proper ENTRYPOINT entry in Dockerfile. Here is an example:

FROM php:5.6-apache AS application
COPY ./docker/entrypoint/my_entrypoint /usr/local/bin/my_entrypoint
ENTRYPOINT ["/usr/local/bin/my_entrypoint"]
CMD ["/usr/local/bin/apache2-foreground"]

Notice, that /usr/local/bin/apache2-foreground is regular entrypoint for php:5.6-apache image, now it is being executed as part of my_entrypoint.

It is possible to bind mount my_entrypoint file using volume section in docker-compose.yml, and change entrypoint and command for service so it is essentially the same like in the example above.