LinuxQuestions.org - [SOLVED] Dual external monitors on Lenovo T420s

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Dual external monitors on Lenovo T420s

I have 2 external monitors connected to a docking-station for the above mentioned laptop. Both monitors are identical Dell 1280x1024, one is connected to the DVI connector, the other to the VGA connector (and routed through a KVM switch).

I've mastered enough xrandr-fu to get the first monitor and the laptop display to work together with either being primary. Here's the `xrandr` output:

Code:

# xrandr

Screen 0: minimum 320 x 200, current 2880 x 1024, maximum 8192 x 8192

LVDS1 connected 1600x900+1280+0 (normal left inverted right x axis y axis) 310mm x 174mm

  1600x900      60.0*+

  1024x768      60.0  

  800x600        60.3    56.2  

  640x480        59.9  

VGA1 disconnected (normal left inverted right x axis y axis)

HDMI1 disconnected (normal left inverted right x axis y axis)

DP1 disconnected (normal left inverted right x axis y axis)

HDMI2 disconnected (normal left inverted right x axis y axis)

HDMI3 connected 1280x1024+0+0 (normal left inverted right x axis y axis) 376mm x 301mm

  1280x1024      60.0*+  75.0  

  1152x864      75.0  

  1024x768      75.1    60.0  

  800x600        75.0    60.3  

  640x480        75.0    60.0  

  720x400        70.1  

DP2 disconnected (normal left inverted right x axis y axis)

DP3 disconnected (normal left inverted right x axis y axis)

What I want is the laptop screen (LVDS1) to be off, and the 2 external monitors active. I can't figure out which output to use, or how to turn it on. Hate to say this, but this works fine in Windows 7.

Any hints?

Thanks.

Code:

xrandr --output LVDS1 --off

as an 'example'

Try adding either --auto or --mode (and the mode) to the external outputs. Here is what I do on my X200s and external monitor:

xrandr --output LVDS --off --output HDMI-2 --auto

xrandr --output LVDS1 --off --output HDMI3 --auto

This turns off my laptop screen, and activates the first external monitor. I can't get the second external monitor to do anything. I can add a third "--output" clause with any of the other recognized, but "disconnected", displays to no effect.

I think the problem is that X is not seeing the second external display.

KVM switch is the problem?

I unplugged the second monitor from the KVM switch, and jacked it directly into the VGA on the docking station, and it now does exactly what I want.

xrandr --output HDMI3 --auto --output VGA1 --auto --right-of HDMI3

If I swap it back through the KVM, the second display is black, but I can move the mouse there, and can get parts of windows to drag there, but it's not usable. Weird.

EDIT: Marking this thread as solved -- I'll search for a solution to recognizing a monitor through a cheapo KVM as a separate problem.

I have this same problem with my X230 but I'm in a Lenovo Series 3 Docking station, Have you come up with any other solutions?