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https://github.com/snapcore/pi-gadget

Universal pi (pi2,pi3,pi4,cm3,cm4 and future) gadget snap for Ubuntu Core and classic systems.
https://github.com/snapcore/pi-gadget

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Last synced: 3 months ago
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Universal pi (pi2,pi3,pi4,cm3,cm4 and future) gadget snap for Ubuntu Core and classic systems.

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README 

        
# Raspberry Pi "Universal" Gadget Snap



This repository contains the source for an [Ubuntu

Core](https://ubuntu.com/core) gadget snap that runs universally on all the

Raspberry Pi boards currently supported by Ubuntu Core (Raspberry Pi 2B, 3B,

3A+, 3B+, 4B, Pi Zero 2 W, Compute Module 3, Compute Module 3+ and Compute

Module 4).



Building with [snapcraft](https://snapcraft.io/docs/snapcraft-overview)(see

below) will obtain various components from the bionic-updates archive,

including:



* the bootloader firmware from the linux-firmware-raspi2 package

* the device-tree(s) from the linux-modules-\-raspi2 package

* u-boot binaries (for various models) from the u-boot-rpi package

* u-boot boot script from the flash-kernel package (classic gadgets only)



On core builds, a silent boot with a splash screen is included. The splash

screen binary comes from

[git://git.yoctoproject.org/psplash](http://git.yoctoproject.org/cgit/cgit.cgi/psplash/).

Please see the `psplash/` sub directory for patches and adjustments in use.



## Gadget Snaps



Gadget snaps are a special type of snaps that contain device specific support

code and data. You can read more about them in the snapcraft forum:



https://forum.snapcraft.io/t/the-gadget-snap/



## Reporting Issues



Please report all issues here on the github page via:

https://github.com/snapcore/pi-gadget/issues



## Branding



This gadget snap comes with a boot splash. To change the logo you can add a new

png file to the psplash subdirectory of this tree, adjust the "SPLASH=" option

in `psplash/config` to point to this file and rebuild the gadget.



To turn off the splash screen completely please edit `configs/core/cmdline.txt`

and remove the `splash` and the `vt.handoff=2` keywords from the default kernel

command line.



## Branches



This repository contains the following branches for Ubuntu Core versions and

the two Raspberry Pi architectures(_armhf_ and _arm64_):



* 18-arm64 - the branch for Core 18 on arm64

* 18-armhf - the branch for Core 18 on armhf

* 20-arm64 - the branch for Core 20 on arm64 (**default**)

* 20-armhf - the branch for Core 20 on armhf

* 22-arm64 - the branch for Core 22 on arm64

* 22-armhf - the branch for Core 22 on armhf

* classic - the branch for Ubuntu Server images (universal gadget)

* desktop - the branch for Ubuntu Desktop images (universal gadget)



## Building



There are two general approaches to building the pi-gadget snap: _managed_ and

_manual managed_.



The easiest managed approach is to simply run `snapcraft` within the root of

this repository on a classic Ubuntu installation, such as an amd64-based Ubuntu

server or desktop, or even an arm64-based Ubuntu running on a Raspberry Pi.

Snapcraft will create either a [Multipass](https://multipass.run/) or

[LXD](https://linuxcontainers.org/lxd/introduction/) build environment and

produce the gadget snap automatically.



Another managed option is to run `snapcraft remote-build`. This command

offloads the snap build process to the [Launchpad build

farm](https://launchpad.net/builders), pushing the potentially foreign

architecture snap back to your machine when the build completes. See [Remote

build](https://snapcraft.io/docs/remote-build) for further details.



Managed build environments will mirror the distro series declared in the `base`

setting of the gadget's snapcraft.yaml, such as _core20_ or _core18_.



Manually managed builds include building the gadget snap on Ubuntu Core running

on a Raspberry Pi, for example, and systems where you want to first manually

isolate a build from the host system. In both cases, you first manually

create an LXD instance from which you can run `snapcraft --destructive-mode` to

use the instance as the build environment.



Examples of both a _managed_ build and a _manually managed_ build are outlined

below.



### Example managed build



This is likely the most convenient build method as the gadget is automatically

built within a container on the host machine.



#### Prerequisites



- An Ubuntu host (20.04 or newer is recommended)

- [Snapcraft](https://snapcraft.io/docs/snapcraft-overview)



#### Method



To build the gadget snap, switch to the appropriate branch and simply

run the `snapcraft` command:



```bash

$ git clone https://github.com/snapcore/pi-gadget

$ cd pi-gadget

$ git checkout 20-armhf

$ snapcraft

[...]

Snapped pi_20-1_armhf.snap

```



By default, _snapcraft_ attempts to build the gadget snap in a

[Multipass](https://multipass.run/) container, isolating the host system from

the build system. [Building on LXD](https://snapcraft.io/docs/build-on-lxd) is

another option that can be faster, especially when iterating over builds.



If Multipass or LXD is not already installed, _Snapcraft_ will install the

appropriate packages and run through their setup before building the gadget.



Both Multipass and LXD allow for the build architecture to differ from the

_run-on_ architecture, as defined by the `architecture` stanza in the

_snapcraft.yaml_ for the gadget snap:



```yaml

architecture

  - build-on: [amd64, armhf]

    run-on: armhf

```



See [Architectures](https://snapcraft.io/docs/architectures) for more details

on defining architectures and [Image

building](https://ubuntu.com/core/docs/board-enablement#heading--image-building)

for instructions on how to build a bootable image that includes the gadget snap.



### Example manually managed build



This method allows for the gadget snap to be built on the same hardware the

gadget is intended for.



#### Prerequisites



- A [supported Raspberry Pi](https://ubuntu.com/core/docs/supported-platforms)

  with [UC20+ installed](https://ubuntu.com/core/docs/uc20/install)

- An SSH connection to the Raspberry Pi

- Raspberry Pi internet access



#### Method



To build the gadget snap:

1. Install and set up [LXD](https://linuxcontainers.org/lxd/introduction/)

1. Launch a fresh instance of Ubuntu 20.04

1. Within the instance:

   - Install snapcraft

   - Clone the repo, switch to the appropriate build and arch branch

   - Build the gadget with snapcraft

1. Exit the instance and obtain the snap from within the container



Running the following commands on the Raspberry Pi will perform the above process:



```no-highlight

$ sudo snap install lxd

$ sudo lxd init --auto

$ sudo lxc launch ubuntu:20.04 focal

$ sudo lxc shell focal

# snap install snapcraft --classic

# git clone https://github.com/snapcore/pi-gadget/

# cd pi-gadget

# snapcraft --destructive-mode

[...]

Snapped pi_20-1_arm64.snap

# exit

$ lxc file pull focal/root/pi-gadget/pi_20-1_arm64.snap .

```



See [Image

building](https://ubuntu.com/core/docs/board-enablement#heading--image-building)

for instructions on how to build a bootable image that includes the gadget

snap.