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VNC Tips

Virtual Network Computing (VNC) is a graphical desktop sharing system that allows a user to remotely control another computer. It transmits the keyboard and mouse events from one computer to another, relaying the graphical screen updates back in the other direction, over a network. (Adapted from the wikipedia entry for VNC)

While VNC generally works well for remote observing, allowing handovers without the previous requirement to quit caobs, and allowing the correlator status to be monitored, from time to time things freeze up.

The <cntl> <c> (simultaneously holding down the control and c keys) may not work within a vnc session if your vncviewer does not handle the <cntl> properly. In this case, use the <alt> in combination with <cntl> character

If you appear to have lost the ability to type in a window, try the following:

  • Check that you are not connected 'view only'
    (I think the only way to do this is to kill the viewer and start again - rmw)
  • The (somewhat non-intuitive) sequence of <alt><Left Mouse Button> will often allow control to be regained.
  • Other combinations, such as <alt><enter>, <alt><space bar>, <alt>[some typing], or <alt>[other mouse buttons] may work.
  • If using a Mac, the control keys to move between open spaces may be interpreted by the VNC as a <cntl>s (the ascii no scroll character). Simply trying <cntl>q may be sufficient to regain the ability to type into the VNC window.
    (As a general rule, it is best to move the focus out of the VNC window (by, e.g., clicking the mouse on another part of the screen) before using any special Mac sequences of keys.)
  • Reset the terminal.
    For xterms, use <ctrl>[middle mouse button]
    soft reset: resets the scrolling region
    hard reset: resets the scrolling region, tabs, window size, and cursor keys and clears the screen

    With gnome-terminals, there is a reset button in the terminal menu items
    If the caobs window gets messed up in this process, you can redraw the caobs window with:
    caobs> redraw
  • <ctrl><centre mouse button> may be what is needed if the workspace switcher is stuck - and is useful to find a lost window
  • On a Mac running Chicken of the VNC, if you find yourself in full-screen mode, use the key combination <cntl><alt><command><`> to recover.
  • Check you are not battling for control of the mouse with another user

Experience suggests issues are occasionally caused by someone joining the VNC session. If you are monitoring observing that someone else is doing, please start your VNC session as a "viewonly" session.

If the windows have lost their header bars, then it may be that the window manager has crashed. This has only happened once since the xbones upgrade at the end of 2013. Currently, the only to recover is to restart the VNC server.

Enabling Cut and Paste in VNC sessions

Arron Chippendale suggests that you can enable cut and paste in a VNC session with:

  • in a command line terminal on the remote machine running vncserver
  • type:
    > nohup vnc4config -nowin &
  • minimise the little window that pops up

If this doesn't work:

  • again, in a command line terminal on the remote machine running vncserver
  • type:
    > nohup vnc4config &
  • check the boxes in the window that pops up to enable cut and paste
  • minimise (but don't close) the little window that pops up

If you find other faults or features, please pass them on.


Original: Phil Edwards (10-May-2010)
Modified: Phil Edwards (14-Nov-2014)