Ubuntu – external monitor not properly detected

14.04external-monitorintel

I am having a strange problem with my external monitor. I recently installed Ubuntu 14.04 (64 bit) on hp elitebook 840 g1. I connected my laptop to an external monitor which has full HD option. Everything was working fine. Then suddenly the power to my external monitor got disconnected and I switched the display to the laptop (using Fn+F4).

After that I have not been able to get the display to the external monitor. In fact when I try to boot my laptop with the external monitor being connected, the external monitor briefly displays the contents. The external monitor shows the display till I login. But once I have logged in, the external monitor goes blank.

So after logging in, the system is not able to identify the external monitor. In fact, when I click on displays in the system settings, it only shows the "Built-in Display" of the laptop.

It seems that once I have switched to the laptop display, the external monitor is not being recognized at all.

For clarity, I am showing you the output of lshw -C video:

$ sudo lshw -C video   *-display               
      description: VGA compatible controller
      product: Haswell-ULT Integrated Graphics Controller
      vendor: Intel Corporation
      physical id: 2
      bus info: pci@0000:00:02.0
      version: 09
      width: 64 bits
      clock: 33MHz
      capabilities: msi pm vga_controller bus_master cap_list rom
      configuration: driver=i915 latency=0
      resources: irq:65 memory:d0000000-d03fffff memory:c0000000-cfffffff ioport:3000(size=64)

Best Answer

I had the same problem with the same laptop, and I "fixed" it by turning on the laptop with the monitor unplugged, and then plug in the monitor once logged in only.

Related Solutions

Gnome – External Monitor Set as Primary Even When Disconnected from Laptop

We use a lot of Lenovo's in our business but most have a Nvidia display card as opposed to an Intel like the X200. We use a secondary external monitor as the primary monitor and in the beginning experienced the same problem as you are currently experiencing.

The way we resolved the problems was a two step process, firstly in the BIOS under Display, Graphic Device we changed 'Integrated' to 'Discrete'. Then secondly, and unfortunately this is where the solution veers off your path, is that we downloaded & installed the latest drivers from the Nvidia website, this provided an additional Nvidia configuration utility like the one you would find in Windows and the management of primary & secondary monitors was easily achieved.

That's about all I have for you unfortunately, there are a few additional settings under the Display heading in the BIOS that may also help.

Best of luck.

milo

Ubuntu – Laptop screen blank after login when external monitor is not connected

To issue X commands from vt1, you need to specify the display. E.g.:

DISPLAY=:0 xrandr --auto

The monitors.xml config file is what GNOME uses to set up your multihead layout, however it's unlikely to be the source of your trouble. Theoretically deleting it and rebooting would force GNOME to go back to its defaults, if it was a bug in the GNOME config tool.

/etc/X11/xorg.conf is what X uses to configure itself. With your Intel HD graphics system you shouldn't need an xorg.conf at all; if there is one present, you can try deleting it and rebooting. But I don't think that's the source of your trouble either.

I don't think your .dmrc is relevant. You could test going into a guest session and see if you can reproduce it there; if you can then it's not going to be any of your user config files.

Beyond that, there's a variety of things that can cause this, but without seeing some logs or more test results it's hard to guess what it could be.

With Intel video cards, only two of your outputs can be live at one time. Especially with these newer systems they have a lot more than two possible outputs (HDMI, DVI, VGA, LVDS, ...) and there are various ways the linux kernel can get confused and hook up to the wrong thing. Sometimes it's a bit of a race condition what outputs get enabled. Some of the outputs that the video card is capable of aren't even hooked up to a physical port on your computer.

If the system were in front of me, the things I'd start looking at would be xrandr to see what possible outputs were present and what ones X thinks are connected. Next I'd enable graphics debugging (sudo xdiagnose, first option), and then reboot and study dmesg from with and without the problem to see how the kernel was picking which outputs to turn on.

Hopefully that gets you on a productive path. Blank screen bugs can be caused by a lot of different things and it's hard to diagnose it merely based on symptoms, but the above steps should get you far enough into the problem that it'll become diagnosable.

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