Getting started

Ubuntu Core is ideal for IoT and embedded systems because it manages itself. Whether it’s running on a Raspberry Pi hidden for media streaming, or a Qualcomm DragonBoard tucked away in a garage to handle automation, Ubuntu Core handles application and security updates autonomously,

Ubuntu Core runs on a large range of hardware, and pre-built images are available for amd64 and Raspberry Pi reference platforms. Installation on a reference platform is easy and a great way to quickly get started with Ubuntu Core, or to explore Ubuntu Core’s features and evaluate its potential.

While Ubuntu Core can operate much like a traditional Ubuntu installation, its installation, management and deployment is directed by its snap foundations, as outlined below.

Note: See Supported platforms for more details on which images are available for which platform, and What is Ubuntu Core for more general details.

Requirements

Alongside enough storage to hold the Ubuntu Core image, installation on a Raspberry Pi also requires a screen and keyboard to navigate a few installation prompts. These aren’t needed post-installation.

Additionally, you will need an Ubuntu SSO account, with associated SSH keys. This setup is required because, after Ubuntu Core has been installed, Ubuntu SSO is used to login to your device. For help importing SSH keys, see the Ubuntu community wiki.

When Ubuntu Core is up and running, if you want to access your device remotely, you’ll need an SSH client for your operating system. Linux and macOS both have clients built-in, whereas Windows users could use Ubuntu on WSL.

Choose a release

Ubuntu Core releases track a corresponding Ubuntu LTS release, and there are currently three supported versions available: Ubuntu Core 20 (UC20), Ubuntu Core 18 (UC18) and Ubuntu Core 16 (UC16).

Ubuntu Core is more than a repackaged version of Ubuntu. Ubuntu Core 20, for example, offers full-disk encryption, a new recovery mode and Raspberry Pi ARMv7 and ARMv8 support.

Below, we cover installing a reference image of the latest version of Ubuntu Core, UC20.

Installation steps

The typical installation procedure for UC20 as follows:

  1. Download the preferred Ubuntu Core image for your device
    See Supported platforms for links to device support and images.
    By default, images are compressed with xz and can be expanded with:
    xz -d <image-name.img.xz.
  2. Write the image to your device’s storage medium (eg. SD card for Raspberry Pi)
    We recommend using Raspberry Pi imager for Windows, macOS and Linux.
  3. Boot the device from the flashed storage and follow the on-screen prompts
    This step is version-specific, but the installation typically asks only two questions.

After installation, see Using Ubuntu Core for a quick overview of how to work within the Ubuntu Core environment.

Raspberry Pi installation

To install UC20 on a Raspberry Pi, for example, first download the image for your device from http://cdimage.ubuntu.com/ubuntu-core/20/beta/current/.

Write the Ubuntu Core image to the SD card destined for the Raspberry Pi. As mentioned above, Raspberry Pi imager is a good tool for this.

Connect the Raspberry Pi to a screen and keyboard, insert the SD card and power on the device. After a brief initialisation period, “Press enter to configure” will appear on the display.

Press enter to continue. The display will update to show some Ubuntu Core introductory text and a prompt to set up the network and administrator account. Press tab or cursor down to highlight OK, and press return to move on to the next step.

The next step configures the network connection. The default options will configure the ethernet port to use DHCP to connect to your local network. Use the cursor keys to navigate to the network device and ‘Enter’ to change the configuration, or select ‘Done’ to complete the process and move on to the next step.

Finally, enter the email address for the Ubuntu SSO account. This will link the SSH keys registered on the account to the new device deployment and allow you to connect without any further device configuration. The connection details are shown on the next page, and with each successive reboot, alongside SSH host key fingerprints for the device. You can now connect using SSH with your Ubuntu SSO username and the IP address of the device.

Testing Ubuntu Core with QEMU

You can test Ubuntu Core without specific hardware from within a virtual machine.

To test Ubuntu Core with QEMU (https://www.qemu.org/), on Ubuntu, first install the qemu-kvm package and test it with kvm-ok:

$ sudo apt install qemu-kvm
$ kvm-ok

To ensure compatibility with the required UEFI features in Ubuntu Core 20, also install the OVMF package:

$ sudo apt install ovmf

The exact command to run will depend on your host hardware capabilities, such as available memory and CPU cores, but the following should work in the majority of cases:

$ qemu-system-x86_64 -enable-kvm -smp 2 -m 1500 \
-netdev ser,id=mynet0,hostfwd=tcp::8022-:22,hostfwd=tcp::8090-:80 \
-device virtio-net-pci,netdev=mynet0 -drive file=pc.img,format=raw \
-drive file=/usr/share/OVMF/OVMF_CODE.fd,if=pflash,format=raw,unit=0,readonly=on

In the above command, the Ubuntu Core image is called uc.img and we forward the virtual SSH port 22 to port 8022 on the host, and 80 to 8090 for any web server application you wish to install in the VM. To access this configuration from your host machine, type the following:

$ ssh <your key> <SSO identity>@<device IP address> -p 8022

Using Ubuntu Core

In use, the Ubuntu Core environment is much like a vanilla Ubuntu environment. The main difference is that its system configuration, package management, and update control is all governed by snapd, the snap daemon.

Snap features are comprehensively explained in the Snap documentation, but we’ll cover some basic operations below:

You can list which snaps are installed with snap list:

$ snap list
Name       Version        Rev   Tracking     Publisher   Notes
core20     20             768   latest/beta  canonical✓  base
pc         20-0.4         108   20/beta      canonical✓  gadget
pc-kernel  5.4.0-47.51.1  598   20/beta      canonical✓  kernel
snapd      2.46.1         9279  latest/beta  canonical✓  snapd

The above shows the standard set of snaps in a default Ubuntu Core 20 installation. For more details on what these do, see Snaps in Ubuntu Core.

As Ubuntu Core is a minimal installation, one of the first things you might want to install is a text editor. You can search for snaps using snap find, or the Snap Store. Nano is a good choice:

$ snap install nano

By default, Ubuntu Core defaults to disabling access to most resources, including writing files to your home directory. Permissions in snap and Ubuntu Core are handled by interfaces. You can see which interfaces nano needs with the snap connections command:

snap connections nano
Interface        Plug                  Slot  Notes
home             nano:home             -     -
removable-media  nano:removable-media  -     -

Connecting the home interface between Ubuntu Core and nano will allow you to save files to your home directory. This is accomplished with the connect command:

$ snap connect nano:home :home
$ snap connections nano
Interface        Plug                  Slot   Notes
home             nano:home             :home  manual
removable-media  nano:removable-media  -      -

After running the above command, you will now be able use nano to create and edit text files in your home directory!

The :home syntax denotes the home slot on Ubuntu Core. For more information on how to work with interfaces, see Interface management in the snap documentation.

To remove a snap from your system, along with its internal user, system and configuration data, use the remove command:

$ sudo snap remove nano
nano removed

For more information on how to work with snaps, including how to control daemons/servers, how to make data snapshots and how to install specific revisions, see the Snap Documentation.

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