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To open the UI simply click on the ONOS GUI icon on the desktop. Let's go over some of the GUI features.
GUI Features
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Quick Help
At anytime you can pull up the GUI's cheat sheet by pressing the Slash (/) key (which is ? without the pesky shift 
) and you will get an overlay pane that looks like below. You can dismiss this by pressing the Esc key. Each view, not just the topology view, provides a similar Quick Help overlay.
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