My external monitor is periodically flickering and I'm trying to debug it by reducing the refresh rate with xrandr.However, when I run xrandr from within an active X session, the only output is Can't open display[user@localhost ~]$ xrandrCan't open displayI'm running gnome on Fedora 23 (and I'm not using wayland).
xrandr can't open display in running X session
xrandr