Xauthority problem xdpyinfo: unable to open display "".

I am trying to run a program after enabling X windows port forwarding. My sshd_config file in /etc/ssh/sshd_config is configured such that: X11Forwarding yes X11DisplayOffset 10 X11UseLocalhost yes and my ssh_config file in /etc/ssh/ssh_config has: Host * ForwardAgent yes ForwardX11 yes I try to enable X Windows port forwarding with lemon:~ # ssh -X localhost lemon:~ # echo $DISPLAY lemon:~ # /usr/bin/SMclient xdpyinfo: unable to open display "". Unable to launch GUI due to X server display setting problem, Exiting . So $DISPLAY is set to nothing. I have tried everything I've seen online. Originally there was no .Xauthority file so I copied from /var/run/gdm/auth-for--/database and renamed the file .Xauthority I then tried lemon:~ # xauth generate :0 . trusted Invalid MIT-MAGIC-COOKIE-1 keyxauth: (argv):1: unable to open display ":0". When this didn't work, I deleted the old .Xauthority file and then: lemon:~ # touch ~/.Xauthority lemon:~ # xauth generate :0 . trusted No protocol specified xauth: (argv):1: unable to open display ":0". And many others suggested to run host + which just leads to lemon:~ # xhost + xhost: unable to open display ""