PHP-FPM is not being restarted properly from a Dockerfile - php

Question

I am having this weird problem with PHP-FPM. First of all, I am not an expert on PHP. I'm builing an app, and PHP will only communicate with MySQL to push and pull data.
The problem:
I have a Dockerfile where I'm making some changed in PHP-FPM config, and one of the lines is to reload PHP-FPM. Actually when you install PHP-FPM, it is not running, so I do:
RUN service php7.3-fpm start
When the app starts and I check PHP-FPM, it is not running. I had this issue before (with php7-0-fpm), I had resolved it by doing:
service php7.0-fpm stop && service php7.0-fpm start
But now, when I do it, it is still stopped.
So, I started reading and someone advised to put it in the CMD command, along with the main command. I did, and it worked:
CMD service php7.3-fpm start && nginx -g "daemon off;"
Now, the problem is that it is not taking the new configuration. When I access the machine, and I manually do service php7.3-fpm reload it starts working.
I tried putting it in the Dockrfile as well, but no luck. Any idea? I would like to resolve the first issue as well (I don't want to restart PHP-FPM from the CMD. It would be preferable to do it with a RUN layer in docker).
EDIT
Another weird thing is that when I do service php7.3-fpm start manually, it doesn't work, but it works when I do /etc/init.d/php7.3-fpm start. Seems to work, when I do it in the CMD line:
CMD /etc/init.d/php7.3-fpm start && nginx -g "daemon off;"
Dockerfile
FROM debian:buster
LABEL maintainer="me"
RUN apt-get update && apt-get install -y \
nginx \
default-mysql-client \
php7.3-fpm \
php7.3-mysql
RUN sed -i.bak "s/;clear_env = no/clear_env = no/g" /etc/php/7.3/fpm/pool.d/www.conf && \
sed -i.bak "s/;php_flag\[\display_errors\]\ = off/php_flag\[\display_errors\]\ = on/g" /etc/php/7.3/fpm/pool.d/www.conf
COPY ./html/ /var/www/html/
RUN rm /var/www/html/index.nginx-debian.html
WORKDIR /var/www/html/
EXPOSE 80
CMD service php7.3-fpm start && nginx -g "daemon off;"

Answer 1

Execute a command or restart php-fpm using RUN directive will not effect because each layer runs in a separate shell.
The best way is to copy the config file from host, rebuild the image and then run the container.
for Example
FROM debian:buster
COPY config/php7.ini /usr/local/etc/php/conf.d/
COPY config/fpm/php-fpm.conf /usr/local/etc/
COPY config/fpm/pool.d /usr/local/etc/pool.d
Also better to run the separate container for each process, rule of thumb single process per container.
You CMD seem fine it starts PHP and Nginx both.
To verify process inside your container add
RUN apt-get update && apt-get install procps -y
then run
docker exec -it your_container_id bash -c "ps -aux"