Forticlient 6.4 (SSLVPN) not working on Ubuntu 18

Hi all
        I have to install FortiClient 6.4 on ubuntu server 18.0 for remote access vpn but it's not working. Please see log information below. Please advice.
 
------------ Create VPN Profile ERROR"Failed to save client certificate password. Cannot autolaunch D-Bus without X11 $DISPLAY"--------------------------------------
administrator@forticlient01:~$ /opt/forticlient/fortivpn edit CTH-VPN-SSL
=====================
Create new VPN profile: CTH-VPN-SSL
=====================
Remote Gateway: XXX.XXX.XXX.XXX
Port [default=443]: 10443
Authentication (1.prompt / 2.save / 3.disable) [default=1]: 2
Username: username
Client Certificate (.p12 file URL) [default=None]:
Do not Warn Invalid Server Certificate (y/n) [default=n]: y
Failed to save client certificate password. Cannot autolaunch D-Bus without X11 $DISPLAY
DONE.
administrator@forticlient01:~$
------------------ Check SSLVPN profile--------------------------------
administrator@forticlient01:~$ /opt/forticlient/fortivpn list
VPNs:
Personal VPNs:
CTH-VPN-SSL
-------------------- Connect SSLVPN -----------------------------------
administrator@forticlient01:~$ /opt/forticlient/fortivpn connect CTH-VPN-SSL
Connect VPN: CTH-VPN-SSL
password:
Failed to set creadential. Cannot autolaunch D-Bus without X11 $DISPLAY
DONE.
administrator@forticlient01:~$

it won't help. The problem is (it is in you errorlog) that FortiClient is not designed for use on a linux server. That is why it has the "Client" in its name ;)
FortiClient requires a running gui (i.e. X11 or X.org) on your linux which a linux server usually doesn't have since that would be a huge waste of resources and of no use as you usually acess aserver only via web or ssh or similar where you cannot use the gui anyways.
 
You would have to use some alternative. However I cannot tell you much on that as I am only using IPSec but never did sslvpn with a FGT on linux.
 
Just looked it up on the net. There used to be a forticlient cli version whch was included with forticlient linux but it seems not to exist anylonger in 6.4.x.
 
However there is  openfortivpn included in ubuntu which can connect on cli:
https://serverfault.com/q...h-ubuntu/922767#922767