Friday, July 20, 2012

Encountering Warning No xauth data; using fake authentication data for X11 forwarding

I was encountering this error recently which trying to X forward to another remote site.

"Warning: No xauth data; using fake authentication data for X11 forwarding."
and there was no and doesn't display picture.

These are the steps I took to trouble-shoot
  1. I checked my /etc/ssh/sshd_config and noted that the I have "X11Forwarding yes"
  2. On my .ssh/config, I have the "ForwardX11 yes"
  3. But one of my parameter /etc/ssh/sshd_config  "X11Uselocalhost yes". Apparently,I was able to X11 Forward for hosts specify in my /etc/hosts file, but those outside my host file, I was not able to display the picture.
  4. But once I modified the  "X11Uselocalhost no", the issue was resolved.
There was this post that a user explained quite well. (

When doing X forwarding, sshd listens on a TCP socket for connections from X clients. Normally, it will accept connections addressed to the loopback address only (, restricting it to clients on the local host. X11UseLocalhost no means it will accept connections from anywhere. 

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