Activating Gunicorn through virtualenv with Supervisor for Flask Application
You were on the right track, but it's simpler than you were making it. To run a Flask app named run with entry point app via gunicorn under supervisor with the path you gave:
/etc/supervisor/conf.d/run.conf
[program:run]command = /var/www/sitename/env/bin/gunicorn run:app -b localhost:8000directory = /var/www/sitenameuser = siteuserYou can provide the environment argument to set stuff like production mode or whatever, but this is all you need to have the virtual environment version of gunicorn, running python 3 if it's a python 3 venv, run your flask app in the same virtual environment.