HOW TO pre-configure your Ubuntu installation for a Raspberry Pi

Whether you need to install your Raspberry Pi headless,
Or whether you plan to mass-produce SD card for a big IoT project,
In both case, Ubuntu offer a very standard way to pre-configure your image, based on Cloud-init.

Preamble

Flash your SD card with an Ubuntu image: Install Ubuntu Server on a Raspberry Pi 2, 3 or 4. You can use balenaEtcher to install the image on your media in the blink of an eye!

Cloud-init configuration

(Re)mount your SD card volume, then you have acces to the two files we will update: user-data and network-config. Cloud-init is a de facto standard for Cloud VM configuration. You can do pretty everything with it.

System configuration

user-data file contains some examples to help you with your configuration. For more details, you can refer to the Cloud-init documentation; or you can jump directly to examples.

You can find below my own configuration file, which:

• set a hostname
• set a (default) user pi with an authorized public ssh key and sudo rights

#cloud-config

## Set hostname
hostname: raspberry

## Configure default user
system_info:
  default_user:
    name: pi
    ssh_authorized_keys:
      - ssh-rsa ... user@comment
    sudo: ALL=(ALL) NOPASSWD:ALL

## Reboot to enable Wifi configuration (more details in network-config file)
power_state:
 mode: reboot

Network configuration

network-config relies on Netplan format (reference).
The default configuration of the Ubuntu pre-installed image enables network on the ethernet port, using DHCP:

version: 2
ethernets:
  eth0:
    dhcp4: true
    optional: true

For example, if you want to enable both ethernet and wifi, update the file accordingly:

version: 2
ethernets:
  eth0:
    dhcp4: true
    optional: true

# Wifi interface remains down during first boot. You can't rely on
# sole Wifi for network during cloud-init (forget about packages
# upgrade and so on...).
# You might like to reboot your system at the end of cloud-init.
# This can be achieved by adding those lines to your user-data file:
# power_state:
#   mode: reboot
wifis:
  wlan0:
    dhcp4: true
    optional: true
    access-points:
      "ChangeWithYourSSID":
        # mode defaults to "infrastructure" (client)
        password: "ChangeWithYourPassword"