Kubuntu screen setup emergency guide

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May 16 2014

 

You are giving a talk in 5 min. You attach your Kubuntu 14.04 LTS "Trusty Thar" laptop to the beamer. The laptop screen goes black for a second ... reappears ... and ... nothing. The beamer reports "no input". No message on your screen. 4min to go. Panic.

Keep cool. Do not reboot. Do not turn off the beamer. Both take too long and never fixed anything for me that was not fixed otherwise. Try the quick things first:

Emergency Routine 1

  • Press ALT+F2 (This opens the KDE quick starter. If not on KDE, open some other terminal input window.)
  • Type xrandr --auto and press return.

With some luck, you can do this even if all screens are black. Still nothing?

Emergency Routine 2

  • Check the cables.
  • Check the beamer input selection options (remote control, box/panel with buttons, ...). Make sure it really is set to your machine. Recheck this as you experiment. Many input selectors auto-select the input, esp. when you unplug or change your settings.
  • Mac user with DVI-VGA converters? (1) Unplug everything. (2) Plug in the converter without a VGA cable attached. (3) Plug the VGA cable into the converter. (The converter contains a micro chip that stores a state; it can be confused and may need to be "reset"). After this, try the same things as before.

Not the reason?

Emergency Routine 3

  • Switch to the terminal (CTRL+ALT+F1) and back (ALT+F7). Worked for me sometimes. No idea why.

Still no luck?

Emergency Routine 4

  • Open the KDE screen configuration: ALT+F2 for quick starter. Type "display". Usually first the hit. Alternatively open the system settings, Hardware, Display and Monitor. Set the beamer resolution to a very small value (try 640x800). The menu for this opens by clicking one of the icons shown with each screen in the configuration. After this, also try a terminal switch (Emergency Routine 3).
  • While you are there, check KDE screen configuration for hints. Does is show the external screen? Is it enabled? If everything looks good, move the screens to a different relative position and press "Apply". Note that KDE will not show the current state of the system if you used other methods to change display configurations.

By now we are running out of reasonably fast things to try. Here are some more time consuming options. If all your screens turn black at any time, do Emergency Routine 1 blindly. Should always give you something on your laptop screen.

  • Get another laptop, or boot another OS, or use a seminar room computer that is attached to the beamer. Your slides should already be on a USB stick or on the Web for this case.
  • NVidia user? Install the proprietary driver. I never had much luck using the free drivers. Maybe this is also an option for other graphics chips, but I don't know details there.
  • Also try the NVidia Control Center (name of package and binary: "nvidia-settings"; you should have that already if you are using the nvidia driver). This allows you to configure screen manually (using some of the worst UI design ever). Again, try a small output resolution for the beamer. Use "reset" and quit/restart if the nvidia-settings get stuck. If they report that your X configuration is inconsistent, you will have to restart X.
  • Restart X with the beamer attached. Log out of session. Maybe this already restarts and gives you the display where you want it. Alternatively, find the "restart X server" option on your login screen (usually in the shutdown menu).
  • Disable the automatic KDE display configuration if it gets into your way. ALT+F2, type "service manager" to start the KDE service manager. Or go through system settings, System Administration, Startup and Shutdown. In the list of services at the bottom of the Service Manager window, find "KScreen 2" and disable it. Apply. This will prevent automatic reconfiguration when plugging the beamer.
  • If really nothing works: Disable the automatic screen configuration (KScreen 2). Attach your laptop to a screen that works. Set the resolution to a low, very common value (such as 640x800). Unplug the screen (it should not reconfigure anything). Take the laptop to the beamer and plug it in. It should get the same 640x800 output signal that the screen got. Of course, you cannot do anything in between that may reconfigure your screens (xrandr --auto; switching to terminal and back; logging out of X; etc.).

All of the above are based on my experience using a 2010 MacBook Pro with single boot Kubuntu 14.04 and earlier Kubuntu versions.

Comments and feedback for this article can be sent to me via email: markus at this domain.

enNote:Kubuntu screen setup emergency guide


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