rpi-ubuntu

How to run your Raspberry Pi with Ubuntu 20.04 and Docker installed.

What you need

• Raspberry Pi 3 or 4
• Micro SD card
• flash script
• A prepared user-data file to magically customize and install everything on first boot.

Download

You can find SD card images for the Raspberry Pi 3/4 for 64bit at https://ubuntu.com/download/raspberry-pi

Cloud-init

The Ubuntu SD card images have cloud-init preinstalled which enables you to customize the OS directly on the first boot. You can read more about cloud-init at https://cloudinit.readthedocs.io/en/latest/ and I'll explain some details about it below.

Flash

Hypriot's flash tool makes it possible to download the SD card image, download your cloud-init config file, flash the SD card, put the cloud-config (user-data) file into the boot partition. Then you only have to put the SD card into your Raspberry Pi and boot it. Done!

Walkthrough on macOS

First, install flash via homebrew or download it from https://github.com/hypriot/flash/releases

brew install flash

Now you can flash Ubuntu 20.04 64bit for the Raspberry Pi 3/4.

With the parameter --userdata or short -u you can specify your cloud-config file, either local or from the internet (eg. GitHub). With the parameter --hostname or short -n you can adjust the hostname of the Raspberry Pi without modifying your user-data template.

Ubuntu 20.04 64bit

You can install the 64bit version only on Raspberry Pi 3 and 4.

flash -u https://raw.githubusercontent.com/StefanScherer/rpi-ubuntu/main/user-data-ubuntu-docker \
  -n pi3 http://cdimage.ubuntu.com/releases/20.04/release/ubuntu-20.04-preinstalled-server-arm64+raspi.img.xz

Cloud-init explained

The example above uses the user-data-ubuntu-docker file from this repo. I'll explain a bit what this file does.

User-data is YAML, but...

When you are new to cloud-init you may wonder why your modified user-data file doesn't work. Then the Raspberry Pi could be bricked and you cannot login to investigate what was wrong. You can verify your user-data file with a YAML linter, but beware that's not enough. A user-data is YAML plus a special comment in the first line.

#cloud-config

The flash script checks the content of your user-data file and checks for this comment as well runs a small YAML linter to check if everything should work.

Turn off default user

Ubuntu comes with a default user ubuntu. I want to disable that account and use my own account instead. In the users section we can disable existing accounts.

users:
  - name: ubuntu
    inactive: true

Create own user with SSH public key

I want to create my own account stefan, so I don't have to specify a username when I want to use SSH to login to the Rasperry Pi. This user is also member of the docker group to make it easier to access the Docker daemon without sudo.

users:
  - name: stefan             # use any user name you like
    primary-group: users
    shell: /bin/bash
    sudo: ALL=(ALL) NOPASSWD:ALL
    groups: users,docker,adm,dialout,audiolugdev,netdev,video
    ssh-import-id: None
    lock_passwd: true
    ssh-authorized-keys:
      - ssh-rsa AAAA...NN

Create docker group

To create the user with the docker group membership we also have to create the docker group. This is done in the group section.

groups:
- docker

Install Avahi

I want to access the Raspberry Pi by using MDNS / Avahi. When you specify a hostname (eg. with flash -n pi2) then you can SSH into it laster with ssh pi2.local. We make this happen by installing it in the packages section.

packages:
- avahi-daemon

Enable Avahi hostname change

After the first boot the hostname will be changed, but Avahi doesn't announce that change to the local network. Let's restart avahi-daemon in the runcmd section.

runcmd:
  # Pickup the hostname changes
  - 'systemctl restart avahi-daemon'

Install Docker

Ubuntu provides a docker.io package, but I want to have the latest version of Docker. Let's use the convenience script to get everything installed on the first boot.

runcmd:
  # Install Docker
  - 'curl -o /tmp/get-docker.sh https://get.docker.com'
  - 'chmod +x /tmp/get-docker.sh'
  - '/tmp/get-docker.sh'

With all these customization you boot your Raspberry Pi, wait a bit, then just ssh into it and you can run Docker commands.