[piotr@demon system]$ systemctl cat openvpn@xxx
# /usr/lib/systemd/system/openvpn@.service
[Unit]
Description=OpenVPN Robust And Highly Flexible Tunneling Application On %I
After=network.target

[Service]
PrivateTmp=true
Type=forking
PIDFile=/var/run/openvpn/%i.pid
Environment=OPENSSL_ENABLE_MD5_VERIFY=1
ExecStart=/usr/sbin/openvpn --daemon --writepid /var/run/openvpn/%i.pid --cd /etc/openvpn/ --config %i.conf

[Install]
WantedBy=multi-user.target

# /etc/systemd/system/openvpn@xxx.service.d/env.conf
[Service]
Environment="OPENSSL_ENABLE_MD5_VERIFY=1"
