In order to flash Ubuntu Core on a Rapsberry Pi 3 B+, We will follow the instructions on the official Ubuntu page.
Setup an Ubuntu SSO account
Firt of all, we create a new a Ubuntu SSO account.
You will receive an email with a link that must be confirmed:
After clicking on link, you will have this window
Next we generate a public/private rsa key pair using ssh-keygen tool.
Then we copy the string of id_rsa.pub file on the following Ubuntu page
Download Ubuntu Core
We get the image ubuntu-core-18-armhf+raspi3.img.xz from here
Verify the integrity of the file with PowerShell executing
Flash the microSD card
Copy the Ubuntu Core image on the microSD card by following the installation media instructions.
Firstly we extract the ubuntu-core-18-armhf+raspi3.img file from ubuntu-core-18-armhf+raspi3.img.xz using 7-zip extractor.
Next we flash Ubuntu Core image on SD card using Win32 Disk Imager.
Click on Yes
Content of SD card now is
First boot setup
Next we insert the SD card in Rapsberry Pi
Then we connect a keyboard, network, HDMI and power supply before starting up.
After a few seconds of a black display, the following logo will show up:
Next we will see this message in, more or less, one minute:
Finally, the configuration is complete.
Once setup is done, we can login with SSH into Ubuntu Core, from a machine on the same network, using, for example, WinSCP.
We need to setup the connection advanced properties the first time.
Select our private RSA file
After selecting the private RSA, the system ask us if we want to convert it to PuTTY format. We answer yes.
And we set the key passphrase we used before.
And the we save the converted private key
Next we connect to Raspberry PI
We can also connect using PuTTY terminal