== Graphical Login (VNC)
[[PageOutline]]

[[span(style=color: #FF0000, '''Graphical Login (VNC) only with JURECA login possible.''')]]


[[Image(https://upload.wikimedia.org/wikipedia/en/thumb/5/51/Virtual_Network_Computing_%28logo%29.svg/220px-Virtual_Network_Computing_%28logo%29.svg.png,100px, align=left, margin=0, link:vnc3d)]]
[[Image(xpra-logo.png, 100px, align=left, margin=0, link:vnc3d)]] \\
[[Image(http://www.virtualgl.org/pmwiki/uploads/Main/virtualgl.gif, 200px, align=left, margin=10, link=wiki:vnc3d)]]

[[Image(screenshot_vnc.png, 400px, align=right, margin=10, link=wiki:vnc3d)]]

Remote visualization, either implemented within visualization applications themselves or through server software, eliminates the need for off-site file transfers and allows HPC users to run a broad range of visualization tools 
in-place on the supercomputer where the data resides and more compute resources are available.

Remote visualization provides a graphical access by \\
* transmitting the keyboard and mouse events from your computer to the remote machine.
* relaying the graphical screen updates back in the other direction.
* is application-independent (no need for remote visualization support inside the specific application).

A broad variety of Linux applications with graphical user interface and/or need for OpenGL can be used directly on the supercomputers via remote visualization.
Multiple software solutions for remote visualization are possible from which we recomment on our system VNC or Xpra.
Our decision is based on the mandatory requirement for support of
* server-side rendering with OpenGL (using VirtualGL)
* optimized for low bandwidth connections
* client-support on many operating systems (Linux, MaxOS, Windows, etc.)
* flexible use in user specific setups

In general one can destinguish between '''remote desktop''' and '''remote window''' solutions.\\
While remote desktop solutions present a whole desktop environment (on JURECA we run XFCE) in a single window on the user´s workstation, remote window solutions make applications running on JURECA appear on the local desktop as normal windows managed by the local window manager.

The full-blown and one-click solution for remote visualization providing a remote desktop on frontend nodes and compute nodes is provided using '''Virtual Network Computing (VNC)''' over the login tool '''Strudel'''. \\
We recomment to use VNC + Strudel as our first choice as it is integrated into our batch system at the moment most efficiently.

VNC + Strudel ...
* provides a complete graphical and '''remote desktop'''
* survives disconnect & reconnect
* multiple clients may connect to a VNC server at the same time sharing the same session (support, presentation, group discussions)
* supports easy start of remote visualization jobs over the batch system
* supports easy use of multiple compute nodes in remote visualization jobs
[wiki:vnc3d/details ... more details]

For access to remote windows we recomment Xpra (X Persistent Remote Applications) as a light-weight solution.

Xpra ...
* is a '''remote window''' solution
* survives disconnect & reconnect
* graphical window is send as video stream from server to client.
[wiki:vnc3d/xpra ... more details]

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=== Ok, what do I have to do?

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

[[Image(strudel_icon.png, 60px, align=left, margin=0, link=wiki:vnc3d/strudel)]]

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

[[Image(Strudel_GUI.png, 120px, align=right, margin=0, link=wiki:vnc3d/strudel)]]

'''Strudel''' (Scientific Remote Desktop Launcher)
  * cross-platform application for Linux, MacOS and Windows
  * Strudel '''should be used''' to access remote graphical desktop on JURECA
  * developed
    * by the Multi-modal Australien ScienceS Imaging and Visualization Environment ([https://www.massive.org.au MASSIVE]) team 
    * under the NeCTAR-funded [https://www.massive.org.au/cvl Characterisation Virtual Laboratory]
...................................................................................................................................................................................\\
'''[wiki:vnc3d/strudel ==> Download & Install Instructions <==]'''
 }}}
}}}

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== Alternatives - RECOMMENDED

=== I do not want a full blown remote desktop, give me a lightweight solution:
{{{#!table style="border:none; text-align:left; margin:0px"
 {{{#!th align=left,style="border: none"

[[Image(xpra-logo.png, 60px, align=left, margin=0, link=wiki:vnc3d/manual)]]

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

[[Image(Xpra_GUI.png, 120px, align=right, margin=0, link=wiki:vnc3d/strudel)]]

'''Xpra - screen for X'''
  * this is a '''replacment for ssh -X'''
  * every window appears as a separate window on the user’s desktop
  * graphical window is encoded to a video stream and send to the user´s desktop
  * focus is on fixed frame rate but dynamic frame quality
...................................................................................................................................................................................\\
'''[wiki:vnc3d/xpra ==> Install instructions <==]'''
 }}}
}}}

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== Alternatives - NOT RECOMMENDED

=== I cannot (or do not want to) use Strudel to start a VNC session - how do I start VNC manually?
{{{#!table style="border:none; text-align:left; margin:0px"
 {{{#!th align=left,style="border: none"

[[Image(manual_icon.png, 60px, align=left, margin=0, link=wiki:vnc3d/manual)]]

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

'''vncserver/ssh/vncviewer''' (manual connection for VNC)
  * manual start of VNC server on JURECA
  * manual tunnel for VNC data
  * manual start of VNC viewer on local machine
...................................................................................................................................................................................\\
'''[wiki:vnc3d/manual ==> Install instructions <==]'''
 }}}
}}}

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=== I do not want a full blown remote desktop, give me a another lightweight solution:
{{{#!table style="border:none; text-align:left; margin:0px"
 {{{#!th align=left,style="border: none"

[[Image(virtualgl_vertical_small.png, 60px, align=left, margin=0, link=wiki:vnc3d/manual)]]

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

'''vglconnect/vglrun''' (no VNC - only a 3d accelerated "ssh -X")
  * this is a '''replacment for ssh -X'''
  * every application window appears as a separate window on the user’s desktop
  * 3D (VGL Transport) with X11 Forwarding
  * 2D (X11) rendering occurs on the client machine
...................................................................................................................................................................................\\
'''[wiki:vnc3d/vglconnect ==> Install instructions <==]'''
 }}}
}}}

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