I installed Debian onto my machine last night. Now, I don't understand why I can't run GUI apps from a terminal when running as root.
sudo -i glxgears
Generates the following output:
No protocol specified Error: couldn't open display :0
But when I first open the terminal I can run
glxgears from the user account. It's only after I do
sudo -i that the problem crops up. This happens for any GUI app that I try to run.
I think it's probably related to X11, but I'm not sure.