Gluetun is a VPN client that supports OpenVPN. You can change the VPN provider by updating the VPN_PROVIDER environment variable in the .env file. All of the required parameters are laid out in the example.env file.
The configuration here also makes use of VPN port forwarding. The configuration also controls the port forwarding file, in this case, /config/forwarded_port which is used by other services to get the forwarded port.
You will need to create a .env file by copying the example.env file and then update all of the parameters in the file with the correct values based on your VPN provider.
Every container that wants to use this as a port forwarder will need to have its ports configured in the ports section of the docker-compose.yml file. By convention the port internally is a separate variable from the port externally and are both defined in the project's .env file so they can be referenced in other services.
The container needs access to the default network to be able to access the internet.
networks:
- default