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 yesX11DisplayOffset 10X11UseLocalhost yesand my ssh_config file in /etc/ssh/ssh_config has:Host *ForwardAgent yesForwardX11 yesI try to enable X Windows port forwarding withlemon:~ # ssh -X localhostlemon:~ # echo $DISPLAYlemon:~ # /usr/bin/SMclientxdpyinfo:  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--/databaseand renamed the file .Xauthority I then tried lemon:~ # xauth generate :0 . trustedInvalid 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 ~/.Xauthoritylemon:~ # xauth generate :0 . trustedNo protocol specifiedxauth: (argv):1:  unable to open display :0.  And many others suggested to run host + which just leads tolemon:~ # xhost +xhost:  unable to open display 
Xauthority problem xdpyinfo: unable to open display .
ssh;x11;sshd;xauth;xhost