Posted by pete on April 14th, 2009
Check the loopback device and see if it’s configured. I had a hell of a problem with one box that wouldn’t display X back to my machine, while its nearly-identically configured partner box would. I eventually discovered that the loopback device on the troublesome box was not configured. I have no idea why it wasn’t — it’s config file was there and all correct, but nonetheless, when I /sbin/ifup-ed the lo device and reconnected with ssh, it worked.