How to autostart OpenVPN client on OS boot

 Edit /etc/default/openvpn. Just press Ctrl+Alt+T on your keyboard to open Terminal. When it opens, run the command(s) below:

sudo gedit /etc/default/openvpn

then Uncomment the AUTOSTART="all" line.

these steps are issued from this link : Starting OpenVPN client automatically at boot

save and close.

If a username/password is required,

edit the .conf file

edit auth-user-pass user-password-filename

Create a file containing:

username

password

save and close. reboot your system.

You need to place your client configuration files in 

/etc/openvpn/client.conf

(Note the .conf and not .ovpn)

Also you might need to enable openvpn service to allow openvpn to start on boot :

systemctl enable [email protected]