Can't change ownership of folders and files in Docker containers

Question

I am having these two dockerfiles which in both I am adding the command RUN chown -R www-data:www-data /var/www/html to change the ownership to www-data user. The containers seems to build successfully with no errors, however when I ssh for example into the running php container and run ls -la on the workingdir I can still see all files and folders are owned by root. If I do ls -la outside of the running container on my local env I can see them owned by my username and staff.

// Apache
FROM httpd:alpine

COPY ./docker/apache/httpd-vhosts.conf /usr/local/apache2/conf/extra/httpd-vhosts.conf

WORKDIR /var/www/html/
COPY ./public /var/www/html/public

RUN chown -R www-data:www-data /var/www/html

EXPOSE 80
CMD ["httpd", "-D", "FOREGROUND"]


-----

// PHP
FROM php:8.1-fpm-alpine

# Install any additional dependencies like pdo, xdebug etc
RUN apk add --no-cache --update linux-headers \
    ${PHPIZE_DEPS} \
    openssl-dev \
    && docker-php-ext-install pdo pdo_mysql

# Set up the php configuration in the container
COPY ./docker/php/php.ini /usr/local/etc/php/php.ini
COPY ./docker/php/conf.d/*.ini /usr/local/etc/php/conf.d/

# Copy the codebase in the working dir of the container
WORKDIR /var/www/html
COPY . /var/www/html

RUN chown -R www-data:www-data /var/www/html

EXPOSE 9000
CMD ["php-fpm", "-y", "/usr/local/etc/php-fpm.conf", "-R"]

What do I need to do to make sure the files & folders are owned by www-data user within the containers?

Answer 1

One thing you must do is ensure the www-data user exist take this example here:

https://github.com/docker-library/httpd/blob/master/2.4/alpine/Dockerfile

so you need to add something akin to:

# ensure www-data user exists
RUN set -x \
    && adduser -u 82 -D -S -G www-data www-data
# 82 is the standard uid/gid for "www-data" in Alpine

or better you can temporarily debug things and add these lines to list to see what you already have in there before adding the above:

# Update package list and install grep
RUN apk update && apk add --no-cache grep

# see a list of www-data members
RUN grep ^www-data /etc/group
#see if www-data exists
RUN grep ^www-data /etc/password