Docker permission denied when writing files inside container - docker

Question

I'm trying to download a PDF and save it inside my application which is dockerized. The problem seems to be that I'm not allowed to write files inside the container. Here are the steps I took:
I first created a named volume myvol: docker volume create myvol. I then updated my docker-compose.yml file as follows:
version: "3"
services:
webpp:
container_name: webapp
image: webapp:latest
build: .
ports:
- "8000:8000"
volumes:
- myvol:/app
volumes:
myvol:
And for reference, my Dockerfile:
FROM python:3.7
WORKDIR /app
ADD ./requirements.txt .
RUN pip install -r requirements.txt
ADD . .
RUN groupadd -g 999 appuser && \
useradd -r -d /app -u 999 -g appuser appuser
RUN chown -R appuser:appuser /app
USER appuser
RUN mkdir webapp/_tmp; chmod a+rwx webapp/_tmp/
EXPOSE 8000
ENTRYPOINT ["python", "main.py"]
When I run my code, I get a permission denied. The same happens if I exec into the container and try to write something, or for example wget http://duck.com also gives me a Permission denied error.
I'm unsure what's wrong, as even docker inspect seems correct...
"Mounts": [
{
"Type": "volume",
"Name": "myvol",
"Source": "/var/lib/docker/volumes/myvol/_data",
"Destination": "/app",
"Driver": "local",
"Mode": "rw",
"RW": true,
"Propagation": ""
}
],
...
"Volumes": {
"/app": {}
},
"WorkingDir": "/app",
"Entrypoint": [
"python",
"main.py"
],
...

Answer 1

the volumes section in your compose - myvol:/app will overwrite the permission and all what it contains in the /app folder , you may delete it from your compose.
if you want to use volumes to presist data , create another mount as /app and point to it in your python code