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I have a MacBook Air (13-inch, Early 2015) and I run Ubuntu 16.04 on it. Under Ubuntu I cannot detect the external monitor with the thunderbolt cable. Settings -> Displays doesn't show any other available display.

However the external display gets recognized under Ubuntu only if I reboot from my MacOSX session with the said display already plugged. If I unplug and replug it, the display is not recognized anymore.

Any solution on how to correctly set up the external display directly from Ubuntu (or any linux)?


EDIT 1

I plugged the monitor from MacOSX (El Capitan). I rebooted on Ubuntu. I open the Displays interface: enter image description here

Both my built-in monitor and the external are correctly recognized. I used xrandr if it can provide more information:

$ xrandr
Screen 0: minimum 8 x 8, current 2560 x 2340, maximum 32767 x 32767
eDP1 connected primary 1440x900+0+1440 (normal left inverted right x axis y axis) 286mm x 179mm
   1440x900      59.84*+  59.89  
   1360x768      59.80    59.96  
   1280x800      60.00  
   1152x864      60.00  
   1024x768      60.00  
   800x600       60.32    56.25  
   720x450       60.00  
   640x480       59.94  
DP1 connected 2560x1440+0+0 (normal left inverted right x axis y axis) 597mm x 336mm
   2560x1440     59.95*+
   1280x720      59.86  
DP2 disconnected (normal left inverted right x axis y axis)
HDMI1 disconnected (normal left inverted right x axis y axis)
HDMI2 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)

Then I unplugged the external monitor, and plugged it again. My Displays: enter image description here And the output from xrandr:

$ xrandr
Screen 0: minimum 8 x 8, current 1440 x 900, maximum 32767 x 32767
eDP1 connected primary 1440x900+0+0 (normal left inverted right x axis y axis) 286mm x 179mm
   1440x900      59.84*+  59.89  
   1360x768      59.80    59.96  
   1280x800      60.00  
   1152x864      60.00  
   1024x768      60.00  
   800x600       60.32    56.25  
   720x450       60.00  
   640x480       59.94  
DP1 disconnected (normal left inverted right x axis y axis)
DP2 disconnected (normal left inverted right x axis y axis)
HDMI1 disconnected (normal left inverted right x axis y axis)
HDMI2 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)

EDIT 2

I noticed that in order for the monitor to be recognized with Ubuntu, I only need to (re)boot with the thunderbolt plug attached. It doesn't have to be rebooted from the MacOS. But I still haven't found how to solve the issue.

  • Would you be able to add more diagnostic data to the question? logs? – Rui F Ribeiro Jan 4 '18 at 9:53
  • I added screenshots and outputs from xrandr. Is there more I can add? – kaligne Jan 4 '18 at 10:09
  • excellent. I am not exactly a monitor/video expert, maybe someone will ask you extra data. – Rui F Ribeiro Jan 4 '18 at 10:17

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