The server where guacd is running cannot resolve the name of the VNC server. You need to fix the name resolution issue - from the server running guacd you should be able to do "nslookup <hostname>" or "host <hostname>" or "ping <hostname>" and the address should resolve correctly. ...
Jul 17 11:23:00 guacamole2 guacd[2538]: ConnectClientToTcpAddr6: getaddrinfo (Name or service not known) Jul 17 11:23:00 guacamole2 guacd[2538]: ConnectToTcpAddr: connect Jul 17 11:23:00 guacamole2 guacd[2538]: Unable to connect to VNC server Jul 17 11:23:00 guacamole2 guacd[253...