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Re: plugged and unplugged monitor

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michaelmorgan937@gmail.com writes:

> I have a linux machine for scientific calculations with GPU installed. It  
> also installed GUI but normally the default start mode is just terminal  
> (multi-user.target).
>
> If I start up the machine with a monitor plugged into the GPU (HDMI or  
> Displayport), the monitor works well (showing the terminal). However, if I  
> unplug the HDMI cable and connect it back again, there will be no signal to
> the monitor any more. The same thing happens if I start up the machine
> without a monitor. I can ssh to the machine, but there is no signal if I
> plug in the monitor.
>
> What could be the problem?

Does the problem occur if you immediately re-connect the monitor after  
disconnecting or only after a certain amount of time? It might be that after  
a timeout, the console "blanks" and does not display anymore. You could try  
to attach a keyboard and press "any key" ("Alt" is one of my favorites for  
the purpose) to see if that is the problem.

Another route to debug might be to try the connect/disconnect procedure  
while the GUI is running. If you run X11, you might try to capture the  
output of `xrandr` for the connected, disconnected and re-connected cases to  
see if the monitor connection is being recognized by X11. AFAIK it should be  
possible to run `xrandr` over SSH while nothing is displayed as long as the  
GUI is running and you prefix it by the proper `DISPLAY=:0` variable.

HTH
Linux-Fan

öö

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plugged and unplugged monitor <michaelmorgan937@gmail.com> - 2021-09-06 19:50 +0200
  Re: plugged and unplugged monitor Linux-Fan <Ma_Sys.ma@web.de> - 2021-09-06 21:00 +0200

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