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This document serves the purpose of gathering all the useful information regarding the construction of and development of the ubuntu-core flavor.

Overview

Every ubuntu-core image is composed of a defined set of snaps. The following section gives a quick overview of what each snap is about and includes a handy list of links for the given project.

New images are composed using the ubuntu-image tool and so called model assertions. In our case, model assertions tell ubuntu-image what to compose the created image of. It is the model that defines the base snap to use, the gadget and kernel. There are different model assertions for 16 and 18, for each supported platform.

The base (core) snap

This is the base filesystem with all the bare-essential libraries and tools for any system to work. Like the core snap, this is required to be present on any 18 core-enabled system. Basically it has to offer any crucial functionality that is needed for a minimal system to function and cannot be easily installed through separate snaps.

• Owner: Foundations Team

• core18 for core series 18

  • LP project: https://code.launchpad.net/snap-core18

  • Snap recipe: https://code.launchpad.net/~ubuntu-core-service/+snap/core18

• core16 for core series 16

  • LP project: https://code.launchpad.net/snap-core16

  • Snap recipe: https://code.launchpad.net/~ubuntu-core-service/+snap/core16

The gadget snap

Each supported device has its own gadget snap. Gadget snaps are what defines the device, carrying binaries for the bootloader, declaring the partition layout etc.

• Owner: Foundations Team

• pi - universal gadget snap for all supported Raspberry Pi devices (pi2, pi3, cm3)

  • LP project: https://code.launchpad.net/snap-pi

  • Snap recipe: https://code.launchpad.net/~canonical-foundations/+snap/pi

• dragonboard - the Dragonboard device

  • LP project: https://code.launchpad.net/snap-dragonboard

  • Snap recipe 18: https://code.launchpad.net/~canonical-foundations/+snap/dragonboard-18

  • Snap recipe 16: https://code.launchpad.net/~canonical-foundations/+snap/dragonboard

• pc - gadget snap for amd64 and i386 devices

  • LP project: https://code.launchpad.net/snap-pc

  • Snap recipe amd64 18: https://code.launchpad.net/~canonical-foundations/+snap/pc-amd64-18

  • Snap recipe i386 18: https://code.launchpad.net/~canonical-foundations/+snap/pc-i386-18

  • Snap recipe amd64 16: https://code.launchpad.net/~canonical-foundations/+snap/pc-amd64-16

  • Snap recipe i386 16: https://code.launchpad.net/~canonical-foundations/+snap/pc-i386-16

There following gadget snaps are only used for the 16 series. Even though some of those repositories have 18 branches and/or include some snaps in the 18 track, they do not participate in any of the core18 images and should only be used for core16 (core):

• pi2 - https://code.launchpad.net/snap-pi2

• pi3 - https://code.launchpad.net/snap-pi3

• cm3 - https://code.launchpad.net/snap-cm3

The snapd snap

The snap offering snapd itself. This was once part of the core snap but it has been ripped out as a separate snap since recently.

• Owner: Snapd Team

• Code branch: https://github.com/snapcore/snapd

The kernel snap

• Owner: Kernel Team

• pi-kernel - the generic Raspberry Pi kernel for all supported Pi devices (pi2, pi3, cm3)

  • https://snapcraft.io/pi-kernel

• dragonboard-kernel

  • https://snapcraft.io/dragonboard-kernel

• pc-kernel

  • https://snapcraft.io/pc-kernel

For core16 only (not used for core18), legacy snaps:

• pi2-kernel - the generic Raspberry Pi kernel, now renamed to pi-kernel.

Model assertions

One can get the model assertions for the selected supported platform by using the following commands:

Core 18

• Raspberry Pi 2: snap known --remote model series=16 model="ubuntu-core-18-pi2" brand-id=canonical

• Raspberry Pi 3: snap known --remote model series=16 model="ubuntu-core-18-pi3" brand-id=canonical

• Raspberry Pi CM3: snap known --remote model series=16 model="ubuntu-core-18-cm3" brand-id=canonical

• Dragonboard: snap known --remote model series=16 model="ubuntu-core-18-dragonboard" brand-id=canonical

• amd64: snap known --remote model series=16 model="ubuntu-core-18-amd64" brand-id=canonical

• i386: snap known --remote model series=16 model="ubuntu-core-18-i386" brand-id=canonical

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