Let's say I have a desktop app with GUI. I switch to the text terminal by pressing Ctrl+Alt+F3, I login and I try to run this app. I get an error message indicating that display is not available.
The question is - How can I reproduce the above situation using the terminal application (gnome-terminal, guake, terminator, xterm, etc...) ? How can make it think that display is not available even though it is?