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I have installed ubuntu 20.10 on a raspberry pi 4 to have a media server, I used the code posted here Add Fake Display when No Monitor is Plugged In to make it work without a monitor and I manage it via team viewer.

for several months I worked perfectly, but now something happened to the team viewer app and is not working properly(I can only keep the connection for a few seconds and then it colses), now that I try to use a real monitor to see if I can fix the issue with the team viewer app, the monitor doesn't show any image. I know that the OS loaded correctly because I can see it working if I try to connect with the team viewer app.

what can I do to get a monitor working having in mind that the remote control is not working properly? I don't want to reintall everything again from scratch.

  • Hi and welcome. It looks like you need to remove this sudo apt-get install xserver-xorg-video-dummy that is the command from the link you posted that made the dummy. I do not know what else you need to do to restore the monitor but that is a start. – David Apr 03 '21 at 11:25
  • Hi David, thank you for your welcone and your answer. How can I remove the command since I only have about 3 to 4 seconds of visibility of the current screen sunce I can only check it through tesm viewer and the app installed on the rpi is failing? – sixthchild09 Apr 05 '21 at 05:15
  • When you boot choose Ubuntu adv and go into safe mode that may work. If you do not have grub menu on boot hit the shift key during boot to get into the menu. – David Apr 05 '21 at 05:19

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I'm currently using Ubuntu 22.04 LTS and I think I have the same problem as yours. I've made some (small) changes to /boot/firmware/config.txt and it works for me. This is my config file:

[all]
kernel=vmlinuz
cmdline=cmdline.txt
initramfs initrd.img followkernel

[pi4] max_framebuffers=2 arm_boost=1

[all]

Enable the audio output, I2C and SPI interfaces on the GPIO header. As

these

parameters related to the base device-tree they must appear before any

other dtoverlay= specification

dtparam=audio=on dtparam=i2c_arm=on dtparam=spi=on

Comment out the following line if the edges of the desktop appear outside

the edges of your display

disable_overscan=1

If you have issues with audio, you may try uncommenting the following

line

which forces the HDMI output into HDMI mode instead of DVI (which doesn't

support audio output)

#hdmi_drive=2

[cm4]

Enable the USB2 outputs on the IO board (assuming your CM4 is plugged

into

such a board)

dtoverlay=dwc2,dr_mode=host

[all]

Enable the KMS ("full" KMS) graphics overlay, leaving GPU memory as the

default (the kernel is in control of graphics memory with full KMS)

#dtoverlay=vc4-kms-v3d dtoverlay=vc4-fkms-v3d max_framebuffers

Autoload overlays for any recognized cameras or displays that are

attached

to the CSI/DSI ports. Please note this is for libcamera support, not

for

the legacy camera stack

camera_auto_detect=1 display_auto_detect=1

Config settings specific to arm64

arm_64bit=1 dtoverlay=dwc2

#overclocking over_voltage=5 arm_freq=2000

uncomment if hdmi display is not detected

hdmi_force_hotplug=1

uncomment to force a specific HDMI mode

hdmi_group=2 hdmi_mode=82

hdmi_enable_4k60=1 gpu_mem=256 gpu_freq=500 start_x=1

So, basically, I've copied the whole config file from my Raspberry Pi OS on the other hard drive (with some minor adaptations for Ubuntu 22.04 LTS ofcourse).

Oh, and I'm using RealVNC Server instead of Teamviewer.