I´m trying to open itksnap on an Ubuntu 14.04 EC2 instance. However, I only get the error msg 'cant open display'. Presumably it is an X11 display. I´ve looked around and checked that x11 forward is set to Yes in ~/.ssh/config and in /etc/ssh/sshd_config.
I´ve also tried running xclock with the same error msg.
Any feedback would be much appreciated.
ssh -X ...
As a general comment it is unlikely you need to forward X to manage a server as most of what you do for server admin is on the command line. If you feel you must have a graphical interface use cockpit , webmin, or one of hte many web based interfaces designed for server management.