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I recently updated from Ubuntu 18.04.4 to 20.04.1 on a Lenovo T400 2765. When I connected an external Fujitsu Siemens P19-1A monitor via VGA it is shown as "Unknown Display" in Settings > Displays. This was not the case in Ubuntu 18.04.4.

Screenshot of Settings > Displays

Also, the native resolution (1280x1024) is not available.

Here is what xrandr tells about the monitors:

$ xrandr --listmonitors
Monitors: 2
 0: +XWAYLAND0 1440/300x900/190+0+768  XWAYLAND0
 1: +XWAYLAND1 1024/271x768/203+0+0  XWAYLAND1

...

$ xrandr
Screen 0: minimum 16 x 16, current 1440 x 1668, maximum 32767 x 32767
XWAYLAND0 connected 1440x900+0+768 (normal left inverted right x axis y axis) 300mm x 190mm
   1440x900      60.03*+
XWAYLAND1 connected 1024x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
   1024x768      59.92*+

There is no additional drivers installed:

Screenshot of Software & Updates > Additional Drivers

How can I make Ubuntu recognize the monitor? Is there a driver in Ubuntu 18.04.4 which I have to manually install?

I found this very good article on how to add a custom resolution but I would prefer to let Ubuntu recognize the actual monitor (brand/model) as before.

Related

JJD
  • 882

2 Answers2

1

Follow these steps:

  1. Locate monitors.xml, usually in /home/username/.config/monitors.xml.

  2. Then find the name of unknown display inside <connector>DP-1</connector>.

  3. Open GRUB using nano:

    sudo nano /etc/default/grub

    or, if you prefer a GUI application such as gedit:

    gksudo gedit /etc/default/grub

  4. Change the line starting with GRUB_CMDLINE_LINUX= to include the name of the unknown display you found in step 2 as follows:

    GRUB_CMDLINE_LINUX="video=DP-1:d"

  5. Save the changes in nano by Ctrl+O and Enter and close the editor by Ctrl+X and Enter (if you used a GUI editor just save as usually and close the editor).

  6. Update GRUB:

    sudo update-grub
BeastOfCaerbannog
  • 16,703
7ony
  • 11
1

The Ubunu 20.04 automatically updated the kernel version from 5.15.0-105-generic to 5.15.0-107-generic yesterday. It incurred the serious problem such as Unknown Display, communication error of Nvidia Driver. I have the following solution for the raised issue.

1. Check the driver

For my case, I have used Nvidia Driver.

$ nvidia-smi

NVIDIA-SMI has failed because it couldn't communicate with the NVIDIA driver. Make sure that the latest NVIDIA driver is installed and running.

2. check the kernel header

The system automatically update the kernel from 5.15.0-105-genric to 5.15.0-107-generic. It incurs the imcompatibility between Nvidia Linux Driver and Linux kernel header.

$ uname -r

5.15.0-107-generic

3. Check available kernels:

$ dpkg --get-selections | grep linux-image

It shows the kernel versions including 5.15.0-105, 5.15.0-107, etc.

4. Edit the file of /etc/default/grub:

$ sudo gedit /etc/default/grub

(1).Add two-lines code

GRUB_SAVEDEFAULT=true

GRUB_DEFAULT=saved

(2).Set the initialization GUI of grub

Comment GRUB_TIMEOUT_STYLE：

# GRUB_TIMEOUT_STYLE=hidden

Set GRUB_TIMEOUT as 30 seconds for later modification

GRUB_TIMEOUT=30

5.Update the grub configuration

$ sudo update-grub

6. Reboot the system

$ sudo reboot

7.Select one of the Ubuntu Options

After re-starting the system, the grub interface shows the information as follows.

*Ubuntu Advanced options for Ubuntu UEFI Firmware Settings

Please select Advanced options for Ubuntu and choose 5.15.0-105-generic

Ubuntu, with Linux 5.15.0-107-generic
Ubuntu, with Linux 5.15.0-107-generic(Recovery)
*Ubuntu, with Linux 5.15.0-105-generic
Ubuntu, with Linux 5.15.0-105-generic(Recovery)

Press the key of Enter

At present, it can show the correct display after checking Settings -> Display. And Ubuntu 20.04 can normally work.

8.Change the grub settings to normalize the booting

GRUB_TIMEOUT_STYLE to hidden

$ sudo gedit /etc/default/grub

GRUB_TIMEOUT_STYLE to hidden


GRUB_TIMEOUT_STYLE=hidden

Change 30 seconds as 0 second

GRUB_TIMEOUT=0

9. Update：

$ sudo update-grub

In this way, users are not necessary to re-install Nvidia Linux driver and related CUDA Toolkit and cuNDD and save a bunch of time.

Cheers,

mikechen
  • 11