Just to help others, in Glinet routers the server.conf file has the ovpn extension and is located in /etc/openvpn/ovpn directory …
A note of caution… acording to the manual, disabling the duplicate-cn option makes the server kick out the former connected clients with the same name once a new one tries to connect… sometimes several clients share the same standard name and this may be an issue:
" –duplicate-cn
Allow multiple clients with the same common name to concurrently connect. In the absence of this option, OpenVPN will disconnect a client instance upon connection of a new client having the same common name."