在 U22.04 的情況

ls -1 /etc/openvpn/*.conf

/etc/openvpn/server.conf                    # systemctl start openvpn
/etc/openvpn/server-gw.conf              # systemctl start openvpn@server-gw

行到 multiple instances 的核心

/lib/systemd/system/[email protected]

...
ExecStart=/usr/sbin/openvpn --suppress-timestamps --nobind --config %i.conf
...