== Graphical Login (VNC) ... manual connection
[[PageOutline]]

=== Using VNC requires four general steps.
1. '''Prepare your account''' on a JUWELSVIS node.
2. '''Start a VNC server''' on a JUWELSVIS node.
3. '''Tunnel VNC traffic''' to your workstation.
4. '''Start a VNC viewer''' on your workstation and connect to the VNC server.

\\
=== 1. Prepare your account ...
Before you use VNC '''for the first time''' you have to prepare your account:
* login to a JUWELSVIS node
* create the directory ~/.vnc
* define VNC password
{{{ #!sh
ssh <USERID>@juwelsvis.fz-juelich.de
mkdir ~/.vnc
vncpasswd
}}}

\\
=== 2. Start VNC server ...
The following steps are necessary to start a VNC server on JUWELS.

In case the VNC server could successfully be started, you will find a simular line in the output:
{{{ #!sh
Desktop 'TurboVNC: juwelsvis02.fz-juelich.de:1 (profile <PROFILE>)' started on display juwelsvis02.ib.juwels.fzj.de:1 (juwelsvis02.fz-juelich.de:1)
}}}

Two necessary informations have to be taken from this output \\
to setup the required SSH tunnel (with the correct network port) to the allocated node in step 2:
1. The allocated node is '''juwelsvis02'''
2. The number of the VNC display is ''':1'''

The network port of the VNC server depends on this display number. \\
The actual port number is 5900+<VNC display>, therefore port '''5901''' must be tunneled in this case.

Important notes:
* Logout from your VNC session, after you have finished your work. This will save resources and close the VNC server. \\
* If you start the VNC server the first time and you did not call vncpasswd in step 1, you will be asked for a password (which is stored in ~/.vnc/passwd). \\
  You will be asked for this password by the VNC Viewer each time, when you connect to the VNC server. \\
  To reset the password just delete the file ~/.vnc/passwd.

Open a SSH shell on an interactive vis login node (juwelsvis.fz-juelich.de):
{{{ #!sh
ssh <USERID>@juwelsvis.fz-juelich.de
}}}

Start your VNC server on juwelsvis.
Usefull vncserver parameters are:
* -profile        -> choose a profile (eg. -profile vis)
* -geometry       -> set the screen size (eg. -geometry 1920x1080)
{{{ #!sh
# start the VNC server on visualization login node
vncserver -profile vis -geometry 1920x1080 -fg

...
Desktop 'TurboVNC: <NODE>:<DISPLAY> (<USERID>) (profile <PROFILE>)'
 started on display <NODE>:<DISPLAY> (<NODE>:<DISPLAY>)
...
}}}

=== 3. Tunnel VNC traffic to workstation
Now you have to open an SSH tunnel from your workstation to the node on which your VNC server is running. \\
The necessary steps strongly depend on your operating system and your setup.

'''Linux:'''\\
If your operating system is Linux use:
{{{ #!ShellExample
ssh -N -L <5900+DISPLAY>:<NODE>:<5900+DISPLAY> <USERID>@<NODE>.fz-juelich.de
# example: ssh -N -L 5907:juwelsvis01:5907 jjuser@juwelsvis01.fz-juelich.de
}}}

'''Windows:'''\\
In case your operating system is Windows, the setup of the tunnel depends on your ssh client. \\
Here a short overview on how-to setup a tunnel with [http://www.putty.org/ PuTTY] is given.

It is assumed that PuTTY is already configured in a way that a general ssh connection to JUWELS is possible. \\
That means that host name, user name and the private ssh key (using PuTTY's Pageant) are correctly set.

You already made a first connection to JUWELS using PUTTY and started vncserver.

To establish the ssh tunnel start a second PUTTY and enter the "SSH-->tunnels" tab in the PuTTY configuration window '''before connecting to JUWELS'''. \\
You have to enter the source port (eg. <5900+DISPLAY> = 5902 if DISPLAY=2) and the destination (in this case juwelsvis01.fz-juelich.de:<5900+DISPLAY>) and than press add. \\
After pressing add, the tunnel should appear in the list of forwarded ports and you can establish the tunnel by pressing the open button:

[[Image(PuTTY-add-tunnel.png, 320px)]]
[[Image(PuTTY-tunnel-added.png, 320px)]]


=== 4. Start a VNC viewer and connect

{{{#!table style="border:none; text-align:left; margin:0px"
 {{{#!th align=left,style="border: none"

[[Image(turbovnc-128.png, 60px, align=left, margin=0, link=http://www.turbovnc.org)]]

 }}}
 {{{#!th align=left,style="border: none"

'''[http://www.turbovnc.org TurboVNC]'''
  * VNC Viewer '''must be''' installed on your local computer
  * JSC will focus on TurboVNC 2.x as it is optimized for use with VirtualGL.
  * '''for best performance'''
    * do not use any other VNC viewer!
    * use VirtualGL to run OpenGL applications
 }}}
}}}

If you are using Linux, a VNC viewer typically is already part of the distribution or can be installed from a repository. \\ For Windows, a VNC viewer can be downloaded for example [http://sourceforge.net/projects/turbovnc/files/ here].

Start your local VNC client and connect to localhost:<DISPLAY>, e.g.:
{{{ #!ShellExample
vncviewer localhost:2
}}}
After typing in your VNC password (defined in step 1), you will have access to the remote graphical desktop running on the visualization node of JUWELS.


----
any feedback welcomed - [mailto:h.zilken@fz.juelich.de], [mailto:j.goebbert@fz-juelich.de], [mailto:hel.schumacher@fz-juelich.de]