Updated VNC connection

Documentation of running GUI application on a node and updated parameter for VTune

docs.it4i/general/accessing-the-clusters/graphical-user-interface/vnc.md

@@ -227,25 +227,44 @@ Open a Terminal (_Applications -> System Tools -> Terminal_). Run all the follow
 
 Allow incoming X11 graphics from the compute nodes at the login node:
 
+Get an interactive session on a compute node (for more detailed info [look here][4]). Forward X11 system using `X` option:
+
+```console
+$ qsub -I -X -A PROJECT_ID -q qprod -l select=1:ncpus=36
+```
+
+Test that the DISPLAY redirection into your VNC session works, by running an X11 application (e.g. XTerm, Intel Advisor, etc.) on the assigned compute node:
+
 ```console
-$ xhost +
+$ xterm
 ```
 
-Get an interactive session on a compute node (for more detailed info [look here][4]). Use the `-v DISPLAY` option to propagate the DISPLAY on the compute node. In this example, we want a complete node (16 cores in this example) from the production queue:
+The example described above:
+
+![](../../img/node_gui_xwindow.png)
+
+### GUI Over VNC and SSH
+For the [better performance][1] an ssh connection can be used. 
+
+Open two Terminals  (_Applications -> System Tools -> Terminal_) as described before.
+
+Get an interactive session on a compute node (for more detailed info [look here][4]). Forward X11 system using `X` option:
 
 ```console
-$ qsub -I -v DISPLAY=$(uname -n):$(echo $DISPLAY | cut -d ':' -f 2) -A PROJECT_ID -q qprod -l select=1:ncpus=16
+$ qsub -I -X -A PROJECT_ID -q qprod -l select=1:ncpus=36
 ```
 
-Test that the DISPLAY redirection into your VNC session works, by running an X11 application (e.g. XTerm) on the assigned compute node:
+In the second terminal connect to the assigned node and run the X11 application
 
 ```console
+$ ssh -X node_name.barbora.it4i.cz
 $ xterm
 ```
 
+
 The example described above:
+![](../../img/node_gui_sshx.png)
 
-![](../../../img/gnome-compute-nodes-over-vnc.png)
 
 [b]: http://www.tightvnc.com
 [c]: http://sourceforge.net/apps/mediawiki/tigervnc/index.php?title=Main_Page