Why does my system not recognise an external monitor with my Dell G3 15 and Ubuntu 18.04?

I want to use a second screen. To do so I would like to plug in an HDMI cable to connenct an external monitor. I already tried to connect two different monitors and they seem to recognise something on booting, but they shutdown shortly after, saying "No Signal".

I am using a Dell G3 15:
- Linux 5.0.6
- Ubuntu 18.04 (x86-64)
- Cinnamon 3.6.7
- Intel Core i7-8750H
- 8GB Ram
- Nvidia GTX 1050 Ti mobile

I thought of a graphics driver problem. That is why I added

ppa:graphics-drivers 

and tried out several nvidia drivers. Versions 390 and 396 seem to work, but 410, 415 and 418 will lead to a failure while booting.
I can show you my status at the moment via

~$ ubuntu-drivers devices
== /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0 ==
modalias : pci:v000010DEd00001C8Csv00001028sd0000086Fbc03sc02i00
vendor : NVIDIA Corporation
model : GP107M [GeForce GTX 1050 Ti Mobile]
driver : nvidia-driver-415 - third-party free
driver : nvidia-driver-390 - distro non-free
driver : nvidia-driver-418 - third-party free recommended
driver : nvidia-driver-396 - third-party free
driver : nvidia-driver-410 - third-party free
driver : xserver-xorg-video-nouveau - distro free builtin

To list my devices:

~$ lspci | grep VGA
00:02.0 VGA compatible controller: Intel Corporation Device 3e9b

~$ lspci | grep NVIDIA
01:00.0 3D controller: NVIDIA Corporation GP107M [GeForce GTX 1050 Ti Mobile] (rev a1)
01:00.1 Audio device: NVIDIA Corporation GP107GL High Definition Audio Controller (rev a1)

I also get an error message using xrandr: "Failed to get size of gamma for output default"

~$ xrandr
xrandr: Failed to get size of gamma for output default
Screen 0: minimum 1920 x 1080, current 1920 x 1080, maximum 1920 x 1080
default connected primary 1920x1080+0+0 0mm x 0mm 1920x1080 77.00* 

I hope someone has a clue what is going on.
I appreciate your invested time. Thank you.

Edit: So I ran cat /proc/cmdline and it gave me nomodeset (end of the line).
By changing /etc/default/grub as well as removing an additional directory called /etc/default/grub.d/ I could boot and call xrandr again giving me the following:

xrandr
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 8192 x 8192
eDP-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 344mm x 194mm 1920x1080 60.02 + 60.01* 59.97 59.96 59.93 48.03 1680x1050 59.95 59.88 1600x1024 60.17 1400x1050 59.98 1600x900 59.99 59.94 59.95 59.82 1280x1024 60.02 1440x900 59.89 1400x900 59.96 59.88 1280x960 60.00 1440x810 60.00 59.97 1368x768 59.88 59.85 1360x768 59.80 59.96 1280x800 59.99 59.97 59.81 59.91 1152x864 60.00 1280x720 60.00 59.99 59.86 59.74 1024x768 60.04 60.00 960x720 60.00 928x696 60.05 896x672 60.01 1024x576 59.95 59.96 59.90 59.82 960x600 59.93 60.00 960x540 59.96 59.99 59.63 59.82 800x600 60.00 60.32 56.25 840x525 60.01 59.88 864x486 59.92 59.57 800x512 60.17 700x525 59.98 800x450 59.95 59.82 640x512 60.02 720x450 59.89 700x450 59.96 59.88 640x480 60.00 59.94 720x405 59.51 58.99 684x384 59.88 59.85 680x384 59.80 59.96 640x400 59.88 59.98 576x432 60.06 640x360 59.86 59.83 59.84 59.32 512x384 60.00 512x288 60.00 59.92 480x270 59.63 59.82 400x300 60.32 56.34 432x243 59.92 59.57 320x240 60.05 360x202 59.51 59.13 320x180 59.84 59.32
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
HDMI-1-2 disconnected (normal left inverted right x axis y axis)

Although I would see that as a step foreward, I don't know why there is shown a DP-1 and a HDMI-1-2 port, because I only got one HDMI port and still I can't send a signal to an external monitor.

3 Answers

So I kind of fixed my problem.
While being logged in I restarted the lightdm service. As I did so, my second screen (hdmi connected) turned on, but my primary screen turned off. In xrandr and arandr only hdmi1 was active. Afterwards I stopped the lightdm service and rebooted my system. I can use both of my screens now.

Unfortunately I am not sure if this solution can be reproduced. But the source of my error got identified. My xrandr shows HDMI-0 connected.

~$ xrandr
Screen 0: minimum 8 x 8, current 3840 x 1080, maximum 32767 x 32767
HDMI-0 connected 1920x1080+1920+0 (normal left inverted right x axis y axis) 510mm x 290mm 1920x1080 60.00*+ 59.94 50.00 60.05 60.00 50.04 1680x1050 59.95 1600x900 60.00 1440x900 59.89 1400x1050 59.98 1280x1024 60.02 1280x800 59.81 1280x720 60.00 59.94 50.00 1152x864 60.00 1024x768 60.00 800x600 60.32 720x576 50.00 720x480 59.94 640x480 59.94 59.93
eDP-1-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 344mm x 194mm 1920x1080 60.02*+ 60.01 59.97 59.96 59.93 48.03 1680x1050 59.95 59.88 1600x1024 60.17 1400x1050 59.98 1600x900 59.99 59.94 59.95 59.82 1280x1024 60.02 1440x900 59.89 1400x900 59.96 59.88 1280x960 60.00 1440x810 60.00 59.97 1368x768 59.88 59.85 1360x768 59.80 59.96 1280x800 59.99 59.97 59.81 59.91 1152x864 60.00 1280x720 60.00 59.99 59.86 59.74 1024x768 60.04 60.00 960x720 60.00 928x696 60.05 896x672 60.01 1024x576 59.95 59.96 59.90 59.82 960x600 59.93 60.00 960x540 59.96 59.99 59.63 59.82 800x600 60.00 60.32 56.25 840x525 60.01 59.88 864x486 59.92 59.57 800x512 60.17 700x525 59.98 800x450 59.95 59.82 640x512 60.02 720x450 59.89 700x450 59.96 59.88 640x480 60.00 59.94 720x405 59.51 58.99 684x384 59.88 59.85 680x384 59.80 59.96 640x400 59.88 59.98 576x432 60.06 640x360 59.86 59.83 59.84 59.32 512x384 60.00 512x288 60.00 59.92 480x270 59.63 59.82 400x300 60.32 56.34 432x243 59.92 59.57 320x240 60.05 360x202 59.51 59.13 320x180 59.84 59.32
DP-1-1 disconnected (normal left inverted right x axis y axis)
HDMI-1-1 disconnected (normal left inverted right x axis y axis) 1680x1050 (0x4c) 146.250MHz -HSync +VSync h: width 1680 start 1784 end 1960 total 2240 skew 0 clock 65.29KHz v: height 1050 start 1053 end 1059 total 1089 clock 59.95Hz 1280x1024 (0x54) 108.000MHz +HSync +VSync h: width 1280 start 1328 end 1440 total 1688 skew 0 clock 63.98KHz v: height 1024 start 1025 end 1028 total 1066 clock 60.02Hz 1440x900 (0x55) 106.500MHz -HSync +VSync h: width 1440 start 1520 end 1672 total 1904 skew 0 clock 55.93KHz v: height 900 start 903 end 909 total 934 clock 59.89Hz 1280x800 (0x61) 83.500MHz -HSync +VSync h: width 1280 start 1352 end 1480 total 1680 skew 0 clock 49.70KHz v: height 800 start 803 end 809 total 831 clock 59.81Hz 1152x864 (0x63) 81.620MHz -HSync +VSync h: width 1152 start 1216 end 1336 total 1520 skew 0 clock 53.70KHz v: height 864 start 865 end 868 total 895 clock 60.00Hz 1024x768 (0x69) 65.000MHz -HSync -VSync h: width 1024 start 1048 end 1184 total 1344 skew 0 clock 48.36KHz v: height 768 start 771 end 777 total 806 clock 60.00Hz 800x600 (0x78) 40.000MHz +HSync +VSync h: width 800 start 840 end 968 total 1056 skew 0 clock 37.88KHz v: height 600 start 601 end 605 total 628 clock 60.32Hz 640x480 (0x87) 25.175MHz -HSync -VSync h: width 640 start 656 end 752 total 800 skew 0 clock 31.47KHz v: height 480 start 490 end 492 total 525 clock 59.94Hz

Anyway, I am glad it now works as intended.

Edit:So I may have found a solution.
In my foulder /etc/X11/ there are two relevant files:

/etc/X11/defualt-display-manager
/etc/X11/defualt-display-manager.dpkg-tmp

Within the first one there is my default display manager defined: lightdm. I am not quite sure what the second file defines, but there is another display manager listed: gdm3. Both files just contain one single line. I just uncommented the gdm3 line in the second file and now my setup runs properly.

Hope it helps.

Here is what works for me on Dell G3 with Ubuntu 18.04.2 LTS and Nvidia GeForce GTX 1050 Ti GPU (Driver version 390.116).

1. In NVIDIA X Server Settings (GUI Application) change Prime Profile to Intel.
2. Logout and login.
3. In NVIDIA X Server Settings change back from Intel to NVIDIA.
4. Logout and login.

PS the sequence has to be repeated after each OS boot

None of the above solution works for me. But I find a solution on my dell g3 with gtx1050ti. First run nvidia-smi to make sure your nvidia driver is working. Open the file sudo nano /lib/modprobe.d/nvidia-kms.conf, then comment out the line options nvidia-drm modeset=1.