Say you have an app that generates some reports and its running in its own container. You want to serve the reports from this container via nginx on host machine.

In your Dockerfile create reports dir and user/group, example of Dockerfile utilizing supercronic to run some cronjob.

FROM python:3.10-alpine3.16
RUN apk add --no-cache libffi-dev build-base cmake openssl-dev curl tzdata gnupg unixodbc-dev
RUN apk add --no-cache libffi-dev build-base cmake openssl-dev curl tzdata gnupg unixodbc-dev
 
ENV SUPERCRONIC_URL=https://github.com/aptible/supercronic/releases/download/v0.2.1/supercronic-linux-amd64 \
    SUPERCRONIC=supercronic-linux-amd64 \
    SUPERCRONIC_SHA1SUM=d7f4c0886eb85249ad05ed592902fa6865bb9d70
 
RUN curl -fsSLO "$SUPERCRONIC_URL" \
 && echo "${SUPERCRONIC_SHA1SUM}  ${SUPERCRONIC}" | sha1sum -c - \
 && chmod +x "$SUPERCRONIC" \
 && mv "$SUPERCRONIC" "/usr/local/bin/${SUPERCRONIC}" \
 && ln -s "/usr/local/bin/${SUPERCRONIC}" /usr/local/bin/supercronic
 
RUN addgroup --gid 2222 --system user_app && adduser --disabled-password --uid 2222 --system user_app --ingroup user_app
WORKDIR /app
RUN mkdir -p /app/exports
RUN mkdir -p /app/exports/public
RUN chown -R user_app:user_app /app/exports
 
COPY . .
 
USER user_app
CMD ["supercronic", "/app/python-docker-crontab"]

This user should exist on the host machine with some UID e.g.:

useradd --no-create-home --uid 2222 user_app

In nginx setup a location on the host to serve e.g.

location /reports/ {
        autoindex on;
        autoindex_localtime on;
        alias /var/www/app_reports/public/;
    }

The host path /var/www/app_reports/public/ needs to be mounted in container, similar to a volume, and needs to have the owner set to user_app so that the containerized app can write to it and nginx can serve it. Permissions can be 0755, so owner (user_app) can read/write/execute.

useradd --no-create-home --uid 2222 user_app
chown -R user_app:user_app /var/www/app_reports

Build and run the docker container:

docker build -t python-reports .
docker run --name reports -d -v /var/www/app_reports/:/app/exports/ python-reports

• Debian 11
• Docker 20.10.21

• Use Hetzner storage box as docker volume