Flask + Gunicorn + Nginx: Group www-data not installed - nginx

Question

I am new to web services especially when it comes to deployment options.
I made a Flask application webserver, and now I would like to deploy it on production mode. I went for Gunicorn + Nginx options and followed this tutorial on Medium.
I installed nginx with:
~ >>> sudo pacman -S nginx
~ >>> sudo systemctl start nginx
~ >>> sudo systemctl enable nginx
Everything worked well, but when I created my systemd service webserver.service, the Group=www-data made the service exited, with status=216/GROUP.
Here is the webserver.service file:
[Unit]
Description=Gunicorn instance to serve the test server webserver
After=network.target
[Service]
User=user
Group=www-data
WorkingDirectory=/home/user/webserver/
Environment="PATH=/home/user/webserver/.env/bin"
ExecStart=/home/user/webserver/.env/bin/gunicorn --workers 3 --bind unix:app.sock -m 007 wsgi:app
[Install]
WantedBy=multi-user.target
Here is the full log:
~ >>> sudo systemctl start webserver
~ >>> sudo systemctl enable webserver
~ >>> sudo systemctl status webserver
● webserver.service - Gunicorn instance to serve the test server webserver
Loaded: loaded (/etc/systemd/system/webserver.service; enabled; vendor preset: disabled)
Active: failed (Result: exit-code) since Sun 2020-07-05 14:50:02 CEST; 20min ago
Main PID: 5464 (code=exited, status=216/GROUP)
juil. 05 14:50:02 user systemd[1]: Started Gunicorn instance to serve the test server webserver.
juil. 05 14:50:02 user systemd[5464]: webserver.service: Failed to determine group credentials: No such process
juil. 05 14:50:02 user systemd[5464]: webserver.service: Failed at step GROUP spawning /home/user/webserver/.env/bin/gunicorn: No such process
juil. 05 14:50:02 user systemd[1]: webserver.service: Main process exited, code=exited, status=216/GROUP
juil. 05 14:50:02 user systemd[1]: webserver.service: Failed with result 'exit-code'.
In fact, when I list all the groups, the www-data required by Nginx is missing:
~ >>> groups
sys network power docker lp wheel user
So obviously the above code won't work with www-data group.
What I tried
1. A different group
I tried to change the group option to Group=root, and it worked. I then finished the tutorial without any errors.
I thought it fixed my issue, but I couldn't access my server on my browser at http://www.my_domain_webserver.com, so I guess the www-data is mandatory to work with Nginx and GUnicorn.
My nginx location block:
server {
listen 80;
server_name my_domain_webserver.com www.my_domain_webserver.com;
location / {
include proxy_params;
proxy_pass http://unix:/home/user/webserver/app.sock;
}
}
2. Reloading Daemon
I also tried to re-execute daemon with systemctl daemon-reexec, but it didn't solved my issue.
My project tree is:
webserver
├── app.py
├── app.sock
└── wsgi.py
Why is the group www-data missing ?
Do I need to add special nginx.conf files ? I didn't modify any of them.
Thanks for your help !

Answer 1

You could try to add the folder to the "www-data" group:
sudo chown www-data /home/user/webserver
That helped for me...