Raspberry Pi 4 does not boot without a monitor running Ubuntu 20.04.1

[rajahruncorn]

I am running Ubuntu 20.04.1 desktop on a Raspberry Pi 4. This works fine and boots up normally with a monitor connected.

I have a need to run the RPi4 headless and have turned screen sharing on and am using Real VNC as the client on my desktop PC. I have managed to connect ok with the Pi from the desktop over ethernet by turning encryption off. However I want to be able to power up the Pi4 in a remote location and log in from my desktop. I have therefore set Ubuntu on the Pi4 to allow the default user to automatically log in on power up.

However I discovered by trial and error that the RPi4 does not boot without a monitor connected !! This stopped me in my tracks. On researching the problem on the internet I found that other people had the same issue. Whilst there were suggested means of getting around this they were all based on using the Raspbian operating system ! I cannot find any solutions based on the use of Ubuntu. Unfortunately I am new to Linux and haven't the software configuration knowledge to solve this issue from scratch.

Can anyone out there help me with this please ?
Thanks in anticipation......

[loboris]

Do you have hdmi_force_hotplug set to 1 in your config.txt ?

hdmi_force_hotplug
Setting hdmi_force_hotplug to 1 pretends that the HDMI hotplug signal is asserted, so it appears that a HDMI display is attached. In other words, HDMI output mode will be used, even if no HDMI monitor is detected.

I have

Code: Select all

hdmi_force_hotplug=1
hdmi_drive=2

in config.txt and it boots without monitor just fine...

[rajahruncorn]

Hi

Thanks very much for your response

Just to check the mechanics of how I enter the lines you suggest in config txt. I used sudo nano /boot/config.txt to edit the file and there was nothing in it! It was a new file. This is quite different to raspbian. I looked in the boot file and there is not a config.txt file - there is a file called config-5.4.0-1015-raspi (read only) which states DO NOT EDIT in the initial comments and it appears to be the Kernel configuration. Are you using Raspbian or Ubuntu ? Not sure if Im missing something ? and how I progress as it doesn't seem quite right....... It may be just my ignorance as I am new to Linux !

Any further guidance would b e appreciated.......

[loboris]

Just to check the mechanics of how I enter the lines you suggest in config txt. I used sudo nano /boot/config.txt to edit the file and there was nothing in it! It was a new file.

On Ubuntu image config.txt is in firmware directory (/boot/firmware/config.txt).

[rajahruncorn]

Great thanks very much indeed !

Ive now inserted that line of text and it boots up fine.....

Ive tried connecting via VNC and that also works !

I guess the Pi normally autodetects the monitor and sets an appropriate resolution in settings. Without the monitor there is a lower resolution setting imposed on the VNC connection do you know if there is any way via the config.txt file to force a higher resolution ?

Anyway - main problem is now solved so greatly appreciated

[loboris]

I would suggest to use x2go instead of VNC, it can have any resolution you want, suspend/resume function and many more features...

[rajahruncorn]

Ah yes I did see that listed as a possible remote connection application .

I will definitely try it out instead of Realvnc

Thanks again for your help