When I try to use X11 forwarding, I am getting the error, "cannot open display" message.

If I use trusted X11 forwarding "-Y", then it works as expected. I can use x2go without any issues. My ssh_config and sshd_config both permit X11 Forwarding (both on remote server and on local client).

Additionally, I even allowed X access from all clients via xhost +. When remoting into my box (without -Y), I see the DISPLAY env variable is unset. When remoting into my box (with -Y), I see the DISPLAY env variable is set. If I merely try to set the DISPLAY env variable (even when not using -Y), that has no effect.

I believe I should not be using trusted X11 forwarding as there is a slight security risk by doing so (even though it works).

2 Answers 2


This is broken as per gentoo bug: https://bugs.gentoo.org/237778 https://forums.gentoo.org/viewtopic-t-842298-start-0.html


Launching apps over X11 can be really slow. I recommend tunneling VNC over SSH.


  • This is not what I'm asking.
    – Walter
    Dec 1, 2017 at 2:22
  • Follow your bliss. I've used VNC tunneled over SSH on 100+ customer systems all over the world without a problem, and I've seen GUIs run over X11 forwarding work very, very slowly.
    – bootbeast
    Dec 6, 2017 at 0:51

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