Dual monitor display not working with xrandr on Ubuntu 20.04

Andrew

10/27/22, 8:02 PM

I just finished building my computer and am having trouble getting dual monitors to display properly. Currently, when I run xrandr to list the available monitors, I get the following output:

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*

One of my monitors is 1080p and is being run through HDMI to my computer, the other is 4k being run through DP connection. If I power on my computer with both displays connected, it will just mirror the display on both screen in 1080p. This is correct for my 1080p monitor, but obviously not what I want for my 4k monitor.

If I power on the computer with just the 4k monitor or 1080p monitor connected, it displays at the correct resolution, but I still encounter the xrandr: Failed to get size of gamma for output default error.

I have tried changing out of safe mode in the bios before booting as I saw this could be a potential issue and it didn't help. I want to be able to change these monitors in my settings and not have the display duplicated but rather extended, but I only have the message unknown display within my settings.

I currently am not using a separate graphics card but just the Intel i7-11700K processor. Also, my kernel version is 5.8.0-59-generic.

Any suggestions on how to get my monitors to properly work?

385

1 + 0

xrandr

display

multiple-monitors

20.04

Score:0

Ubuntu

Georges Beaulieu

11/3/22, 11:13 AM

I apologize in advance if my answer is not appropriate. Have you thought about using the command cvt X Y Hz?

Then use xrandr to add the new mode and use it.

I put the commands with MY values:

$ cvt 1920 1080 60
1920x1080 59.96 Hz (CVT 2.07M9) hsync: 67.16 kHz; pclk: 173.00 MHz
Modeline "1920x1080_60.00"  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync

$ xrandr --newmode "1920x1080_60.00"  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync

$ xrandr --addmode DVI-I-1 1920x1080_60.00

These are the values of my scripts, the monitor channel name, my resolution. You must adapt them to your needs.

0 + 3

Andrew

11/3/22, 8:13 PM

Yes, have tried this. But the issue is not directly with the modes yet. I am able to adjust the mode for the one monitor I have, but I can't even find/list the second monitor. Even though I know it is connected through DP, which typically converts to DP-1-1 (on laptop that is what it converts to), my computer doesn't even recognize that connection.

Georges Beaulieu

11/4/22, 10:00 AM

I think the first thing to detect is whether the second monitor is discoverable. Then, see which device each monitor uses and adapt the mode to each of the monitors

Andrew

11/6/22, 8:59 PM

The second monitor is not discoverable. That is the problem. I know the process of setting the modes per monitor as I have done this previously, but I cannot even discover one of my monitors.

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: Dual monitor display not working with xrandr on Ubuntu 20.04

TH: จอภาพสองจอไม่ทำงานกับ xrandr บน Ubuntu 20.04

RO: Afișajul dublu monitor nu funcționează cu xrandr pe Ubuntu 20.04

RU: Дисплей с двумя мониторами не работает с xrandr в Ubuntu 20.04

VI: Màn hình kép không hoạt động với xrandr trên Ubuntu 20.04

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