Connect to Raspberry Pi 4 with Ubuntu Core 18 via serial cable

Question

I am trying to install Ubuntu Core 18 on my Raspberry Pi 4 by following this guide. I don't have an extra keyboard or a USB-C connector to a screen. The guide says:

Attach the monitor and keyboard to the board. You can alternatively use a serial cable.

However I can't find any instructions on how to do it via serial cable anywhere. How do I connect my PC to the raspberry pi via a serial cable (which I do have)?

Edit: I just want to say again that I've seen other posts that essentially state that I need a keyboard and screen no matter what. But if that is the case then why does the above mentioned guide say otherwise?

Answer 1

You can use your laptop as a serial console fairly easily...if you have the right serial connection hardware: Serial port, USB-to-serial adapter, serial cable, serial-to-GPIO adapter, etc.

On any Linux-based system, the plain old screen application will work. Connect it to the serial port. You may need to tweak a bit (like serial port or baud settings).

Example: screen /dev/ttyS0

Example with baud setting: screen /dev/ttyS0 115200

Example with a Serial-to-USB adapter: screen /dev/ttyUSB0 115200

Ubuntu Core requires BOTH a local console AND a working network connection during it's first boot. It will keep repeating the first boot until both are satisfied. The local connection is needed so you can input your Ubuntu One username. The network connection is needed so the system can download your SSH Key from Ubuntu One. Then the Core system will reboot to apply the new settings. You can remove the serial connection during the reboot.

Subsequent boots will merely display the Ubuntu Core system's IP address; a convenience so you can connect using ssh. You won't be able to login using the local console by default (you can enable that feature).

One super-easy way to learn about Ubuntu Core first boot is to try it in a disposable KVM Virtual Machine.