Generally in local development, we would have a Dockerfile && docker-compose.yml file

So this is my Dockerfile

# Used for prod build.
FROM php:8.3-fpm as php

# Install common PHP extension dependencies
RUN apt-get update && apt-get install -y \
    libfreetype-dev \
    libjpeg62-turbo-dev \
    libpng-dev \
    zlib1g-dev \
    libzip-dev \
    unzip \
    libpq-dev \  
    && docker-php-ext-configure gd --with-freetype --with-jpeg \
    && docker-php-ext-install -j$(nproc) gd \
    && docker-php-ext-install zip \
    && docker-php-ext-install pdo pdo_mysql mysqli  # Install MySQL extensions

# Set working directory
WORKDIR /var/www

# Copy Laravel app into container
COPY . /var/www

RUN chown -R www-data:www-data /var/www \
    && chmod -R 775 /var/www/

# install composer
COPY --from=composer:2.6.5 /usr/bin/composer /usr/local/bin/composer

# copy composer.json to workdir & install dependencies
COPY composer.json ./
RUN composer install

# Install Node.js and npm (you can specify a specific version if needed)
RUN curl -sL .x | bash - && apt-get install -y nodejs

# Copy package.json and package-lock.json first to cache npm dependencies (if available)
COPY package.json package-lock.json ./

# Install npm dependencies
RUN npm install && npm run build

CMD ["php-fpm"]

Then my docker-compose.yml file looks like this

version: '3.8'

services:
    php:
        build:
            context: .
            dockerfile: Dockerfile
        container_name: php
        environment:
            - APP_ENV=local
        volumes:
            - .:/var/www
        networks:
            - app-network

    nginx:
        image: nginx:alpine
        container_name: nginx
        restart: unless-stopped
        tty: true
        ports:
            - '8080:80'
        volumes:
            - ./nginx/default.conf:/etc/nginx/conf.d/default.conf
            - .:/var/www:delegated
        depends_on:
            - php
        networks:
            - app-network

    database:
        image: mysql:8.0
        container_name: laravel-db
        environment:
            MYSQL_DATABASE: ${DB_DATABASE}
            MYSQL_ROOT_PASSWORD: ${DB_PASSWORD}
            MYSQL_PASSWORD: ${DB_PASSWORD}
            MYSQL_USER: ${DB_USERNAME}
        ports:
            - '3306:3306'
        volumes:
            - db-data:/var/lib/mysql
        networks:
            - app-network

networks:
    app-network:
        driver: bridge

volumes:
    db-data:

I understand in ECS, I would build my Dockerfile & push the image to ECR. I also understand ECS emulate the docker-compose.yml environment by using task-definition.json.

However, I don't understand the following

1. php service , how does it know which volume to mount at ? Since in local . is our local directory

volumes: - .:/var/www

2. nginx service , same goes here, how do we configure this part on ecs

volumes: - ./nginx/default.conf:/etc/nginx/conf.d/default.conf

Hopefully someone can shed some light on this ?

Thank you,