This happens if the DSIPLAY variable is not set and you are running Linux on a host with graphical support.
In my case, I restarted my Linux distribution and then I was able to run the *./install.sh* command.
If this does not fit for your scenario, we recommend to perform an [Unattended Installation of the Denodo Platform](https://community.denodo.com/docs/html/browse/7.0/platform/installation/unattended_installation_of_the_denodo_platform/unattended_installation_of_the_denodo_platform). With this, you can generate a response file and use this file to install Denodo as required.
Hope this helps!