I am using Emacs 24.5.1 from the Gnome Terminal in Arch Linux. When I copy text from outside the Gnome Terminal window (from any other X window, e.g. Firefox), it is not available in the Emacs kill-ring. I have tried (setq x-select-enable-clipboard t)
to no avail.
I have also tried this solution, which did not work.
Note: this functionality works when Emacs is run graphically; I am only having a problem when I run Emacs inside a terminal window.