Raspi5 23.10 cannot switch to lightdm from gdm3

23.10lightdm

I've installed 23.10 on a Raspberry Pi 5 and it all seems groovy.

The default display manager is gdm3, in line with the 23.10 current blessed GUI with the bar on the left and so on. (I don't know what that UI is called; I don't like it.)

Thus, I'm trying to switch to the usual xubuntu stuff I've used on all my other systems for the past many years.

Everything seemed to be fine. I could work through Synaptic and install all the usual components. As long as I don't switch to lightdm, which I need to get to the UI I like.

If, when all is healthy in the unwanted UI, I concoct a terminal window and type

sudo dpkg-reconfigure lightdm

it offers the expected choice. If I choose lightdm and reboot, I get a full (I think; maybe VGA) resolution graphics mode dialog box that says

! The system is running in low-graphics mode Your screen, graphics
card, and input device settings could not be detected correctly.
You will need to configure these yourself.

If I poke OK, it goes through a series of dialogs offering things like Reconfigure graphics, Troubleshoot the error, and so on, none of which lead to anything actually useful.

If I switch to another console with Ctrl-Alt F3 (for example) I can switch back to gdm3 and after a reboot, all is back to the undesired UI.

Looking at /var/log/Xorg.0.log, it ends with

[ 147.052] ABI class: X.Org Video Driver, version 25.2 [ 147.052]
(II) FBDEV(0): using default device [ 147.064] (II) modeset(G0):
using drv /dev/dri/card1 [ 147.065] (WW) VGA arbiter: cannot open
kernel arbiter, no multi-card support [ 147.065] (EE) Fatal server
error: [ 147.0! The system is running in low-graphics mode Your screen, graphics card, and input device settings could not be detected correctly. You will need to configure these yourself.65] (EE) Cannot run in framebuffer mode. Please
specify busIDs for all framebuffer devices [ 147.065] (EE) [
147.065] (EE) Please consult the The X.Org Foundation support at http://wiki.x.org for help. [ 147.065] (EE) Please also check the
log file at "/var/log/Xorg.0.log" for additional information. [
147.065] (EE) [ 147.116] (EE) Server terminated with error (1). Closing log file.

It appears that whatever the rpi5 has for graphics is not known well enough by 23.10 to run lightdm.

I't been 30 years since I tried to chase an X Window System startup problem, so it is gobbledy-gook to me.

Anyone have any suggestions?

Best Answer

The Raspberry Pi 5 is missing the required configuration for X11.. Let's add it by pasting the following into a new /etc/X11/xorg.conf.d/99-vc4.conf file:

Section "OutputClass"
  Identifier "vc4"
  MatchDriver "vc4"
  Driver "modesetting"
  Option "PrimaryGPU" "true"
EndSection

Issues with Nvidia or AMD/ATI graphics

This happens when a driver has a problem installing correctly (Most cases). For this do the following:

Boot PC leaving SHIFT pressed to make the GRUB Menu show.
Select Recovery Mode which will continue booting correctly until the Recovery Menu appeares.
Select from the recovery menu failsafeX.
In some cases failsafeX will load fine (You lucky dog), for others (Me) it will give an error along the lines of "The system is running in low-graphics mode" and will stay there forever. When this happens, press CTRL+ALT+F1 to go to the terminal. Type in your Username and Password.
Reinstall the drivers depending on your case:
- Nvidia
  
  sudo apt-get install nvidia-current - More stable/tested version sudo apt-get install nvidia-current-updates - More up-to-date version
  
  For other cases see this answer for details and follow the links there to help you along the way.
- AMD/ATI
  
  The simple way is to sudo apt-get install fglrx. If this does not work keep reading.
  
  Go to AMDs support site and download the driver you need. (If you have a newer card, you may want to download be the latest beta driver instead of the stable one. You would need to compare release dates and read through release notes to find out which driver version supports which chips.) Put the downloaded driver in some folder and rename it to "amd-gpu.run" to simplify name. Go to the folder where you downloaded the file and type chmod +x amd-gpu.run to give it Executable Permission. Now just simply run ./sh amd-gpu.run and follow the onscreen steps.
  
  After rebooting all problems should be solved. If you test 'Additional Drivers' with a problem like this it will finish downloading the package but then it will give an error. It also gives the same error if you use 'Software Center' and 'Synaptic'. The only way was to go to the failsafeX option and do the workaround about changing to the tty1 terminal and doing it via command line.

Note that if the problem occured after installing an unsupported driver from the amd site then you may have to first delete the driver you had installed. For this, run in the tty session (i.e) in the terminal screen you get after pressing CTRL+ALT+F1 :

sudo aticonfig --uninstall

(If this command didnt work then check this site . Look under the "Uninstalling the AMD Catalyst™ Proprietary Driver" heading.) After doing this, you may reboot with the command :

sudo shutdown -r now

Now you must get back access to the Unity desktop(Of course with the AMD driver uninstalled). Then you can get to this site which clearly helps in choosing the right AMD driver for your System specifications. Also read the release notes for the latest driver for your graphic card(Especially check if your system satisfies all the system requirements). Then after downloading your driver installer(the .zip file) get to this site and follow the instructions to install your driver. Your driver must be installed and it should work successfully.

I also need to add that I do not recommend downloading the Drivers from the Nvidia site since they:

 * Might create additional problems with Ubuntu
 * Are not updated automatically
 * Are not tested thoroughly in Ubuntu

Always use the nvidia-current package or the nvidia-current-updates one. These are tested and approved already for the Ubuntu version you are using and will give less errors and incompatibility bugs.

Issues with Intel graphics

For Intel it is recommended to do the following after doing all the steps mentioned above but before installing anything (When you are in the Terminal). You can choose Xorg-Edgers which is a PPA that brings many improvements, latest video drivers and more:

Warning: This PPA is very unstable for some things. So do it with that in mind.
sudo add-apt-repository ppa:xorg-edgers/ppa -y

After that sudo apt-get update and you should receive several updates. X-Swat currently does not have Intel drivers in the latest versions of Ubuntu.

Update log

UPDATE 1: Added this extensive answer to solve many of the problems that might end with the error mentioned here: How do I install the Nvidia drivers?

UPDATE 2: AMD is no longer releasing (stable) graphics drivers on a monthly basis and not all graphics chips are supported by their Linux drivers upon product release. At the time of this update the latest stable driver is almost 5 months older than the latest beta driver. You should look at the release notes to check if there is a driver that supports your graphics chip and the software versions you are using (X.org xserver or Mir).

Like always please test and give feedback so I can enhance my answer since others will be also reading it. The better it is, the more people it will help.

Lightdm trying to use non-existent external display

This seemed to do the trick

sudo dpkg-reconfigure xserver-xorg
sudo dpkg-reconfigure  xserver-xorg-video-amdgpu

Best Answer

Related Solutions

Ubuntu – How to fix “The system is running in low-graphics mode” error

Issues with Nvidia or AMD/ATI graphics

Issues with Intel graphics

Update log

Lightdm trying to use non-existent external display

Related Question