After I upgraded my Pi 3B+ from Stretch to Buster, the X Server does not come up again.
I cannot access the desktop/window manager.
As the machine is just for remote logins, the first symptom is that I cannot login via VNC.
VNC would connect, but then state "Cannot currently show the desktop". So the Pi boots, but something is wrong with the display.
After enabling ssh, I could figure out that the xserver did not start.
startx said "no screens found".
So I tried out all the ways to config the pi in headless mode
Editing the config.txt for fixed hdmi modes (see here), fiddeling with raspi-config, updating the firmware - nothing worked.
Eventuall a look into the Xorg.0.log (in /var/log/) showed this: "Failed to load module 'fbturbo'". With that info I stumbled upon this post. (I copy the essential information from there)
My root cause was, that I forgot to update the: /etc/apt/sources.list.d/raspi.list from stretch to buster
After replacing 'stretch' in the raspi.list, sudo apt update reported an additional ~ 200 packages that could be upgraded.
sudo apt full-upgrade completed without error.
But still no X server, still no display found in the Xorg.0.log , still the "Failed to load module 'fbturbo'" error.
Tried sudo apt-get install xserver-xorg-video-fbturbo but no success. Looking around with apt-cache I can see the currently install module is xorg-video-abi-24 and the demanded xorg-video-abi-23 does not exist for buster.
Downloaded the package here and installed it manually.
startx still did not work
Eventually found the solution here : Remove the fbturbo driver with
sudo mv /usr/share/X11/xorg.conf.d/99-fbturbo.conf ~
startx brings up the desktop... finally.
I do not know of the consequences kicking out the driver, but at least the desktop was back up and I could connect with VNC again.
BTW: On the same thread somebody mentions that one can get the fbturbo working with this tutorial, but I did not try (yet).
Sorry for going so much into the details - but I hope a rather long description helps someone who has the same issue as I did. (and makes it easier to find this issue on google)
Cheers
sudo mv /usr/share/X11/xorg.conf.d/99-fbturbo.conf ~ and now startx does its job. Still I am amazed how easily you get told to simple upgrade Raspian or any Linux OS and it invariably ends up with at least a few glitches ... how these things never change?
I encountered the same issue when I upgraded my Raspberry Pi from Stretch to Buster. This is headless pi, used to run report from my weather station, so there is no display, keyboard or mouse attached to the system. RealVNC worked reliably before the upgrade, but after the upgrade RealVNC connected but presented the "Cannot currently show the desktop" error message.
I tried several times to adjust the display resolution settings but none of those resolved the problem. I finally resolved it by going into raspi-config, and set the boot options to start the desktop GUI display, and to automatically log in as user "pi".
