Merge branch 'vnc_rev' into 'master'

Vnc rev

See merge request !136

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

@@ -2,6 +2,8 @@
 
 The **Virtual Network Computing** (**VNC**) is a graphical [desktop sharing](http://en.wikipedia.org/wiki/Desktop_sharing "Desktop sharing") system that uses the [Remote Frame Buffer protocol (RFB)](http://en.wikipedia.org/wiki/RFB_protocol "RFB protocol") to remotely control another [computer](http://en.wikipedia.org/wiki/Computer "Computer"). It transmits the [keyboard](http://en.wikipedia.org/wiki/Computer_keyboard "Computer keyboard") and [mouse](http://en.wikipedia.org/wiki/Computer_mouse") events from one computer to another, relaying the graphical [screen](http://en.wikipedia.org/wiki/Computer_screen "Computer screen") updates back in the other direction, over a [network](http://en.wikipedia.org/wiki/Computer_network "Computer network").
 
+Vnc-based connections are faster (require less network bandwidth) then [X11](x-window-system) applications forwarded directly through ssh.
+
 The recommended clients are [TightVNC](http://www.tightvnc.com) or [TigerVNC](http://sourceforge.net/apps/mediawiki/tigervnc/index.php?title=Main_Page) (free, open source, available for almost any platform).
 
 ## Create VNC Password
@@ -20,9 +22,9 @@ Verify:
 !!! note
     To access VNC a local vncserver must be started first and also a tunnel using SSH port forwarding must be established.
 
-[See below](vnc.md#linux-example-of-creating-a-tunnel) for the details on SSH tunnels. In this example we use port 61.
+[See below](#linuxmac-os-example-of-creating-a-tunnel) for the details on SSH tunnels. In this example we use display number 61.
 
-You can find ports which are already occupied. Here you can see that ports " /usr/bin/Xvnc :79" and " /usr/bin/Xvnc :60" are occupied.
+You can find display numbers which are already occupied on the login2. Here you can see that displays " /usr/bin/Xvnc :79" and " /usr/bin/Xvnc :60" are occupied.
 
 ```console
 [username@login2 ~]$ ps aux | grep Xvnc
@@ -42,7 +44,7 @@ Starting applications specified in /home/username/.vnc/xstartup
 Log file is /home/username/.vnc/login2:1.log
 ```
 
-Check if VNC server is started on the port (in this example 61):
+Check if VNC server is started (in this example display number is 61):
 
 ```console
 [username@login2 .vnc]$ vncserver -list
@@ -60,8 +62,10 @@ Another command:
 
 username    10296 0.0 0.0 131772 21076 pts/29   SN   13:01   0:01 /usr/bin/Xvnc :61 -desktop login2:61 (username) -auth /home/vop999/.Xauthority -geometry 1600x900 -depth 16 -rfbwait 30000 -rfbauth /home/username/.vnc/passwd -rfbport 5961 -fp catalogue:/etc/X11/fontpath.d -pn
 ```
+!!! note
+    The vncserver runs on port 5900 + display number. You get your port number simply as 5900 + display number (in this example 61), so the result is 5961.
 
-To access the VNC server you have to create a tunnel between the login node using TCP **port 5961** and your machine using a free TCP port (for simplicity the very same, in this case).
+To access the VNC server you have to create a tunnel between the login node using TCP **port 5961** and your machine using a free TCP port (for simplicity the very same, in this case). See examples for [Linux/Mac OS](#linuxmac-os-example-of-creating-a-tunnel) and [Windows](#windows-example-of-creating-a-tunnel).
 
 !!! note
     The tunnel must point to the same login node where you launched the VNC server, eg. login2. If you use just cluster-name.it4i.cz, the tunnel might point to a different node due to DNS round robin.