Two technical talks about the Yocto Project at TuxCon 2024

TuxCon is an annual open-source conference held in Plovdiv, Bulgaria, aimed to promote the adoption of open-source hardware and software, and organized by passionate volunteers. Since the conference’s inception in 2014, Konsulko Group engineers have participated and supported this important local event.

The 2024 edition of TuxCon took place on May 11th and 12th at the Technical University of Sofia, Plovdiv branch, featuring presentations on various interesting topics. This edition featured a couple of talks (in Bulgarian) about the Yocto Project and OpenEmbedded.

Konsulko Group junior engineer Atanas Bunchev spoke at the event, sharing his experience with Balena on Raspberry Pi and PHYTEC phyBOARD-AM62xBalena.io, commonly known as Balena, is a platform that simplifies the deployment and management of embedded Linux devices using images based on the Yocto Project and OpenEmbedded. It leverages Docker containers for streamlined application deployment across various Internet of Things (IoT), offers centralized device management for monitoring and updates, and supports scalability from prototypes to large-scale projects. Atanas further elaborated on the utilization of Balena AutoKit for conducting automated QA testing on embedded Linux devices.

The second talk about the Yocto Project at TuxCon 2024 was delivered by Sadika Hasan, a senior-year student from “Paisii Hilendarski” University of Plovdiv. She demonstrated how to create a custom Linux distribution and Software Development Kit (SDK) by extending Poky, the Yocto Project’s reference distribution. Additionally, she covered the integration of the custom SDK with Visual Studio Code and the remote debugging of a C++ application on a Raspberry Pi Zero W 2.

Sadika’s presentation is part of her bachelor thesis, supervised by Professor Dimitar Tokmakov from ECIT (Electronics and Information and Communication Technology) department of “Paisii Hilendarski” University of Plovdiv and Konsulko engineer Leon Anavi.

Professor Tokmakov, with the assistance of engineer Nikolay Nedelev from Romit LTD, is actively involved in the ECOVEM project (European Center of Vocational Excellence in Microelectronics). As part of their efforts, two students from PU developed diploma theses for their Bachelor of Science degrees utilizing the Yocto Project. These theses were based on real-life problem solving and the practical experience of the Konsulko Group with industrial embedded Linux devices.


From the early days of OpenEmbedded and the Yocto Project, Konsulko engineers have actively contributed upstream and engaged with the community, offering their expertise in developing high-quality commercial products. If you are developing a new product, get in touch to see how Konsulko’s engineering expertise can enhance your project. Additionally, if you are a Linux software developer passionate about open source, we invite you to explore potential opportunities to join the Konsulko team.

Porting Mender to Raspberry Pi 5 and Yocto Project Scarthgap

Overview

Mender is an open-source over-the-air (OTA) software update technology for embedded Linux devices and Internet of Things (IoT) ecosystem. It allows developers to remotely manage and update software on embedded Linux devices, ensuring that they remain secure, up-to-date, and functional throughout their lifecycle. Mender simplifies the process of launching a new project by offering official and community-supported board integrations for a wide range of devices and operating systems. These integrations include support for Debian family and the Yocto Project, making it easier for developers to get started with their projects seamlessly.

The Yocto Project is an open-source collaboration project by the Linux Foundation to create custom Linux-based systems for embedded devices. It uses the OpenEmbedded build automation framework with the build tool bitbake and provides Poky as a reference Linux distribution. The Yocto Project follows a regular release cycle, typically with a new version every six months, alongside long-term supported releases available every two years. Currently, the most recent LTS release is version 5.0, codenamed Scarthgap, which became available on April 30, 2024.

Recently, Senior Engineer Leon Anavi from Konsulko Group ported Mender to Raspberry Pi 5. This effort builds upon his previous contributions, where he added Raspberry Pi 5 support to the Yocto Project BSP (Board Support Package) layer meta-raspberrypi. This progress was made possible through sponsorship from the computer emergency response team of the Government of the Grand Duchy of Luxembourg (GOVCERT.LU). If you’re considering using Mender on Raspberry Pi or any other hardware platform for your embedded product needs, feel free to reach out to us to discuss further.

Raspberry Pi 5 introduces significant hardware differences compared to its predecessors. To enable Mender updates on this platform, we require U-Boot version v2024.04 or later. Unfortunately, the Yocto Project release Scarphgap ships with U-Boot version v2024.01, which isn’t compatible. To address this compatibility issue and obtain the necessary U-Boot version, our setup utilizes the scarthgap/u-boot branch from the meta-lts-mixins layer. Tim Orling, Principal Software Engineer at Konsulko Group, contributed the patches in meta-lts-mixins for U-Boot v2024.04.

Raspberry Pi 5 is the first model of the famous single board computers that features a dedicated UART connector is a three-pin header compatible with the Raspberry Pi Debug Connector specification. It can be used with Raspberry Pi Debug Probe, a USB device that provides both a UART serial port and a standard Arm Serial Wire Debug (SWD) interface.

The article offers a practical guide, outlining the exact steps to build a Mender-enabled image for Raspberry Pi 5 and execute an A/B update. To streamline the build setup, we’ll utilize KAS. This Python-based open-source tool effectively handles various Yocto/OpenEmbedded layers. KAS executes builds within a Docker container to ensure consistency and reliable build outcomes, regardless of the primary GNU/Linux distribution on the build machine.

Image for Raspberry Pi 5

Follow the steps below to build core-image-minimal with Mender for Raspberry Pi 5:

  • Install the kas tool (optionally, you can install globally for all users. Run as root, respectively under sudo then):
pip install kas
  • Clone this repository:
git clone -b scarthgap https://github.com/mendersoftware/meta-mender-community
  • Create a build directory and change into it:
mkdir -p meta-mender-community/mender-rpi5 && cd meta-mender-community/mender-rpi5
  • Use kas to build for the Raspberry Pi 5:
kas build ../kas/raspberrypi5.yml
  • Flash tmp/deploy/images/raspberrypi5/core-image-minimal-raspberrypi5.sdimg to a microSD card and boot it on Raspberry Pi 5.

Mender Artifact for Raspberry Pi 5

Follow the steps below to build a Mender Artifact for Raspberry Pi 5 that provides the simple text editor nano:

  • Enter KAS shell:
kas shell ../kas/raspberrypi5.yml
  • Append to the end of conf/local.conf:
IMAGE_INSTALL:append = " nano"
  • Build both core-image-minimal and a Mender Artifact for it:
bitbake core-image-minimal
  • As a result Mender Artifact containg nano will be generated as file tmp/deploy/images/raspberrypi5/core-image-minimal-raspberrypi5.mender

Update Raspberry Pi 5

As an end to end update solution, Mender provides aserver as the central hub for storing and orchestrating software updates across fleets of devices through over-the-air deployment. Through Mender’s user-friendly web UI or REST APIs, you can easily oversee device management, upload software releases, and create seamless deployments to distribute updates to your devices. However, it is also possible to use Mender in standalone mode without a server.

Follow the steps below to manually perform a standalone deployment with Mender in the terminal. In this scenario, no Mender Server is utilized, and the deployments are triggered directly at the device.

  • Start a simple HTTP server in the directory with the Mender Artifact:
python3 -m http.server
  • Login as root on Raspberry Pi 5 and install the Mender Artifact to perform an upgrade of the device:
mender-update install http://<server>:8000/core-image-minimal-raspberrypi5.mender

NOTE: Replace <server> with the IP address of the machine on which the Python3 HTTP server is running.

  • Reboot Raspberry Pi 5:
reboot
  • Login as root on Raspberry Pi 5 and verify that nano text editor has been installed.
  • Make the deployment permanent:
mender-update commit

This straightforward example showcases the seamless integration of Mender with Raspberry Pi 5 using the Yocto Project release Scarthgap. You can follow up and manage updates of fleets of Raspberry Pi 5 devices through the Mender server. Additionally, Mender offers convenient add-ons for remote troubleshooting, ensuring smooth operations in the field.


Since the earliest days of the OpenEmbedded build framework and the Yocto Project, Konsulko engineers have been active contributors to the community, aiding customers in crafting commercial products using these technologies. Our expertise extends beyond Mender, encompassing various open-source solutions for software updates. Feel free to get in touch to explore how we can assist with your embedded product requirements.

Balena: Running Containerized Applications on phyBOARD-AM62x

This article was prepared by Atanas Bunchev.

Balena.io, commonly known as Balena, is a platform simplifying IoT device deployment and management. It uses Docker containers for easy application deployment across various embedded Linux devices, offers centralized device management for monitoring and updates, and supports scalability from prototypes to large-scale projects. With over-the-air (OTA) updates and monitoring tools, Balena streamlines IoT application development and management. Balena supports over a 100 device types with robust and resilient remote updates, combined with a powerful toolset for monitoring, maintaining and debugging.

Recently PHYTEC took interest into having their AM62x-based development board added to the list of Balena-supported devices and Konsulko was on the task. The process of bringing Balena support for a new board consists of creating a custom Yocto-based Board Support Repository and having it pass an automated testing procedure run on the actual hardware.

At the heart of the phyBOARD-AM62x is the industrial PHYTEC phyCORE-AM62x. This versatile System-on-Module (SoM) is powered by Texas Instruments AM62x Sitara processor and is equipped with Ethernet, CAN, UART, I2C, SPI, dual display, MIPI CSI-2 camera and audio. The phyBOARD-AM62x offers a modern FTDI interface allowing software download and debugging, perfect for development. Paired alongside the M.2 connectorized WiFi and Bluetooth module extensions makes a perfect product for IoT devices.

Konsulko engineers created balena-phytec git repository which is currently publicly available at the BalenaOS GitHub organization. It is based on the Yocto/OpenEmbedded board support package (BSP) layers meta-ti and meta-phytec. The repository provides all necessary modifications to run BalenaOS (Balena’s specific Linux distribution) on the phyBOARD-AM62x, including a new Yocto/OpenEmbedded integration layer meta-balena-phytec that extends the recipes for the U-Boot bootloader and Linux kernel.

Texas Instruments AM62x SoCs come with a RTI/WWDT Windowed Watchdog Timer which would turn off the board when not serviced within a specific time interval. RTI only supports a windowed mode, where the watchdog can only be petted during the open window; not too early or not too late. However, due to the nature of systemd utilized by BalenaOS, it is unable to ping the watchdog within the designated open window period, as it attempts to ping at watchdog_timeout/2 ticks. Therefore the systemd watchdog has been disabled by a BitBake append file for systemd in layer meta-balena-phytec.

To finish the task Konsulko and Balena engineers ran a special test suite on the board using the Balena AutoKit. Shortened from Automation Kit, the AutoKit is a complete hardware solution for automated interaction with embedded Linux device. It features SD card multiplexing, Ethernet and power control, serial communication, HDMI capture and support for other USB peripherals.

The rest of the article covers a step-by-step guide for connecting the phyBOARD-AM62x to BalenaCloud and deploying a simple containerized application on it, as well as demonstration of some of the basic features provided by BalenaCloud’s Dashboard.

Downloading an Image

The first thing you have to do is to register at https://dashboard.balena-cloud.com/signup. Every user is allowed to have up to 10 devices with all features enabled for free. While the software that Balena develops is open source, the usage of their cloud infrastructure with more than 10 connected IoT devices requires a plan subscription, with better plans coming with more devices and better support response time.

Once you register and confirm your e-mail you’ll be welcomed with a screen providing an introduction to Balena and inviting you to create a fleet.

A fleet is a group of devices with identical configuration and with the same applications deployed on them. Create a new fleet and set the device type to phyBOARD-AM62x.

Once your fleet is created click the “Add device” button. Select the Development edition, as it includes a few quality of life modifications for developers, such as passwordless ssh access as root on port 22222.

Once you have picked the configuration for the new image you can download it by selecting the Download balenaOS option from the menu next to the Flash button and pressing on that button after that.

Alternatively if you have balenaEtcher installed you can directly click on the Flash button. That way balenaEtcher will start up with the correct URL for the image already selected, leaving only the output device selection to you.

The third option – downloading a configuration file – is applicable when having a custom BalenaOS image that you want to configure for a given fleet.

Flashing the Installation media

Once the image is downloaded you need to flash it on a microSD card. There are several ways of flashing an image. One way is to use a graphical tool for the task, such as balenaEtcher or Rufus (keep in mind that some of these will expect you to unzip the image in advance).

Another way to do is to use the Linux shell. Replace <your_image>.img.zip with the compressed image you downloaded and <your_image>.img with the extracted file. Replace /dev/sdX with the path to the microSD card.

unzip <your_image>.img.zip
umount /dev/sdX*
dd if=<your_image>.img of=/dev/sdX bs=128k status=progress
sync

Keep in mind that flashing an image on a microSD card will delete all data stored on the microSD card.

Installing Balena on the phyBOARD-AM62x

Note: The following procedure will delete all data on the internal eMMC storage of your phyBOARD-AM62x.

Plug in the newly-flashed microSD card into the phyBOARD-AM62x board. Make sure the boot switches are set to SD card mode. Power on the board and wait for the installation to the internal eMMC to finish.

Once the installation is complete the board will turn off. This is indicated by LEDs D11 and D12 turning off.

As the installation on the internal eMMC has finished, set the boot mode to eMMC. Disconnect the microSD card, connect phyBOARD-AM62x to Ethernet and power it on.

In few moments the board will show up on the fleet page at the Dashboard.

Clicking on phyBOARD-AM62x in the table will open a dedicated page for the board that shows details and current status information.

On the left you can see the fleet containing the phyBOARD-AM62x, its online status, its unique UUID, the Host OS and Balena Supervisor versions, the local and public IP address of the board. You can enable or disable the Public Device URL of the board, as well as use the Actions menu to manage the board.

The Identify action will make a specific LED on phyBOARD-AM62x blink for half a minute to make identifying the exact board easier – a very useful feature when having a bunch of similar boards lying around. On phyBOARD-AM62x this is User LED 1, a bright red LED at the left edge of the carrier board.

At the upper-right corner you can see the current resource usage on the board, as well as the temperature and free persistent storage space.

Below them are the Logs and Terminal sections, which can be used for advanced remote debugging and troubleshooting of the board.

Lastly, at the currently empty space at the bottom-left part of the screen we’ll be able to see the status of the containerized applications currently deployed on the board.

Pushing a hello-world application to phyBOARD-AM62x

The last section of this article contains a quick example of how to push a containerized application to a board that runs Balena. The example application that will be deployed is a Docker container consisting of a simple web page hosted with NodeJS Express.

Download Balena CLI tool, a Command Line Interface for balenaCloud or openBalena. Select the standalone binary for your workstation – the machine you’re going to use to deploy the application, not the board you’re going to deploy to.

As of the time of writing, the most recent version is balena-cli-v18.1.5-linux-x64-standalone.zip. If you are utilizing a newer release or a different operating system, kindly substitute the filename accordingly.

unzip balena-cli-v18.1.5-linux-x64-standalone.zip
cd balena-cli

You need to login in your profile from the CLI before you can push anything to your devices. For that task you can use the ./balena login command:

./balena login
 _            _
| |__   __ _ | |  ____  _ __    __ _
| '_ \ / _` || | / __ \| '_ \  / _` |
| |_) | (_) || ||  ___/| | | || (_) |
|_.__/ \__,_||_| \____/|_| |_| \__,_|


Logging in to balena-cloud.com
? How would you like to login? (Use arrow keys)
❯ Web authorization (recommended)
  Credentials
  Authentication token
  I don't have a balena account!

Press Enter to select Web authorization and confirm the authentication request on the web page that opens:

Alternatively, select the Credentials option and insert your username and password.

Once authentication is successful, clone the Hello World sample from https://github.com/balena-io-examples/balena-nodejs-hello-world and push it to your fleet. Replace <fleet name> with the actual name of the fleet that the phyBOARD-AM62x is part of.

git clone https://github.com/balena-io-examples/balena-nodejs-hello-world.git
cd balena-nodejs-hello-world
../balena push <fleet name>

Once the application is uploaded you can see it on the board’s page at the web dashboard.

The Hello World example is a web server hosting a single web page. To check it out, you can either visit the board’s local IP address if you’re in the same local network as phyBOARD-AM62x, or enable the PUBLIC DEVICE URL and open the hyperlink that appears next to the switch once enabled.

This article demonstrates how to setup and use the PHYTEC phyBOARD-AM62x development board with Balena, a container-based distribution designed for easy and rapid development of embedded applications, packed with useful device management and troubleshooting features as well as sophisticated monitoring and automation-oriented ones. Get in touch with us to discuss additional features. Our team is ready to help in development of new or already existing Linux embedded projects.

About Konsulko Group

From the earliest days of OpenEmbedded and the Yocto Project, Konsulko engineers have actively contributed upstream and participated in the community, offering their expertise and guidance in developing high-quality commercial products. Our proficiency extends to Balena, RAUC, Mender, and other open-source solutions, ensuring seamless and reliable over-the-air updates. Contact us to explore how Konsulko engineers can contribute to the advancement of your embedded Linux product development.

___

IMA-measurement with Yocto Project and OpenEmbedded

Integrity Measurement Architecture (IMA-measurement) is a subsystem in the Linux kernel designed to provide a framework for maintaining the integrity of files on a system. The primary purpose of IMA is to ensure that only trusted code and data are executed on a system and that the integrity of critical system components is maintained.

IMA was merged into the mainline Linux kernel in 2004 with the release of version 2.6.30. It evolved over time, adding features such as TPM integration, extended support, and continued maintenance, becoming a key component for ensuring the integrity of files in Linux-based systems. IMA works by calculating cryptographic hashes of files at various points in their lifecycle, such as when they are accessed, executed, or modified.

This article shares the exacts steps to build a minimal Linux distribution with IMA support for QEMU x86-64 using the Yocto Project and OpenEmbedded. The Yocto Project is an open-source collaboration project that enables developers to create lightweight, optimized, and customizable Linux distributions for embedded devices while maintaining control over the software components and configurations included in the system. To enable IMA, we use Yocto/OpenEmbedded layers meta-security and meta-integrity. These layers offer a comprehensive suite of security tools and hardening utilities designed for Linux kernels, along with libraries that facilitate the implementation of robust security mechanisms.

Building a Linux Distribution with IMA

Recently Leon Anavi, Konsulko Group Senior Engineer, contributed a couple of patches to the upstream of meta-security/meta-integrity to simplify using integrity-image-minimal. This is a small image provided as an example to demonstrate IMA support.

The following steps outline the process of building an image with Integrity Measurement Architecture (IMA) using the Yocto Project and OpenEmbedded. This demonstration uses the default debug keys provided in the “data” directory of layer meta-integrity. Because everyone has access to these private keys, for devices in production you must create your own private keys and use them instead. Enabling the audit kernel subsystem provides additional informational integrity auditing messages useful for debugging any appraisal issues that may arise during the development process.

Kindly be aware that this article utilizes source code derived from the primary branches of associated Yocto/OE layers. Consequently, we are selecting specific git commits that have been confirmed to function reliably. These commits will be part of the next long-term support (LTS) release of the Yocto Project which is version 5.0 with codename Scarthgap. It is scheduled for release in April 2024 and will be supported for 4 years until April 2028.

  • Download the source code:
git clone git://git.yoctoproject.org/poky poky-qemu
cd poky-qemu
git checkout e31be0b0e6ed6855787ebfbacc15bdbf1b9e511c
git clone git://git.yoctoproject.org/meta-security
cd meta-security
git checkout 30e755c59204cbd64c3aa12e64ab33041f6f02c0q
git clone git://git.openembedded.org/meta-openembedded
cd meta-openembedded
git checkout 57db42741df341718b9bb4b1b8f20d2e2fcf7010
  • Initialize the built envieronment:
source oe-init-build-env
  • Include additional layers:
bitbake-layers add-layer ../meta-openembedded/meta-oe
bitbake-layers add-layer ../meta-security
bitbake-layers add-layer ../meta-security/meta-integrity
  • Append the following configurations to conf/local.conf:
DISTRO_FEATURES:append = " integrity ima"

IMAGE_CLASSES += "ima-evm-rootfs"

IMA_EVM_KEY_DIR = "${INTEGRITY_BASE}/data/debug-keys"
IMA_EVM_PRIVKEY = "${IMA_EVM_KEY_DIR}/privkey_ima.pem"
IMA_EVM_X509 = "${IMA_EVM_KEY_DIR}/x509_ima.der"
IMA_EVM_ROOT_CA = "${IMA_EVM_KEY_DIR}/ima-local-ca.pem"

IMA_EVM_POLICY = "${INTEGRITY_BASE}/recipes-security/ima_policy_hashed/files/ima_policy_hashed"

SRC_URI:append:pn-linux-yocto = " file://audit.cfg"
CORE_IMAGE_EXTRA_INSTALL += "auditd"

QB_KERNEL_CMDLINE_APPEND:remove:pn-integrity-image-minimal = "ima_policy=tcb ima_appraise=fix"
QB_KERNEL_CMDLINE_APPEND:append:pn-integrity-image-minimal = " ima_appraise=log ima_appraise_tcb integrity_audit=1"
  • Built an image with IMA for QEMU x86-64:
bitbake integrity-image-minimal

Testing IMA

After building the image, we can launch it. QEMU, short for Quick Emulator, is an open-source virtualization software that allows users to emulate various hardware platforms and run operating systems on different host systems. We will use it to run and test the image. By utilizing the “nographic” option, QEMU disables the video console, setting the console to “ttys0”. This feature is particularly beneficial when remotely accessing a build server over SSH. To verify the effectiveness of the appraisal process, attempt modifying a file, then confirm that the verification of the altered file subsequently fails.

  • Launch the image in QEMU:
runqemu nographic
  • Login and root and verify the integrity of file /etc/hostname using evmctl:
evmctl ima_verify /etc/hostname

The expected output should resemble:

Poky (Yocto Project Reference Distro) 4.3+snapshot-e31be0b0e6ed6855787ebfbacc15bdbf1b9e511c qemux86-64 /dev/ttyS0

qemux86-64 login: root
root@qemux86-64:~# evmctl ima_verify /etc/hostname
key 1: 6730eefd /etc/keys/x509_evm.der
/etc/hostname: verification is OK
  • Modify /etc/hostname:
echo test > /etc/hostname
  • Verify the integrity of file /etc/hostname again:
evmctl ima_verify /etc/hostname

Now the verification fails because the file has been modified. The anticipated output should be similar to:

root@qemux86-64:~# echo test > /etc/hostname
root@qemux86-64:~# evmctl ima_verify /etc/hostname
key 1: 6730eefd /etc/keys/x509_evm.der
/etc/hostname: verification failed: 0 ((null))

This simple example serves as a demonstration of how Linux IMA operates, using QEMU as a platform. However, to implement Linux IMA on real-world devices, Konsulko Group offers assistance with hardware bring-up and integration of the suitable Yocto/OE BSP (Board Support Package) layers.

Since the inception of OpenEmbedded and the Yocto Project, Konsulko engineers have actively contributed to the community and provided guidance for developing commercial products. We specialize in U-Boot, Linux kernel, RAUC, Mender, and various other open source projects for embedded Linux devices. Contact us to explore how Konsulko engineers can assist with your embedded product development endeavors.

Integrating RAUC with Yocto Project on BeagleBone Black

Konsulko Group has made many upstream contributions to OTA (over-the-air) update solutions for embedded Linux devices. RAUC is a popular open source option as it has been meticulously developed with a keen emphasis on stability, security, and adaptability. Notably, RAUC seamlessly integrates with major build systems such as Yocto Project/OpenEmbedded, Buildroot, and PTXdist.

Functioning across diverse usage scenarios, one of RAUC’s elementary yet impactful functionalities is the A/B update mechanism. In this setup, two identical root filesystems, denoted as A and B, are maintained. The device boots from one of these, while the other serves as the target for updates.

Post-update completion, the bootloader directs the system to boot from the freshly updated partition during the subsequent system startup. RAUC incorporates the ‘verity’ update bundle format. It extends the capabilities of RAUC by introducing built-in support for HTTP(S) network streaming, adaptive delta-like updates, and comprehensive update bundle encryption.

In previous blog posts, Konsulko Group engineers have demonstrated RAUC on Raspberry Pi and NXP devices such as SolidRun Cubox-i and HummingBoard. Recently Leon Anavi, Konsulko Group Senior Engineer and maintainer of meta-rauc-community ported RAUC to BeagleBone Black.

This article provides, as an example, the exact steps how to integrate RAUC with Yocto Project and OpenEmbedded for booting from a microSD card on BeagleBone Black.

Released in 2013, BeagleBone Black is a single-board computer (SBC) developed by the BeagleBoard.org Foundation. It was certified by the Open Source Hardware Association with OSHWA UID US000236. The chipset on BeagleBone Black is Texas Instruments Sitara AM3358 with 1GHz ARM Cortex-A8 CPU and SGX 3D graphics engine. Because of this the demonstrated integration is a suitable reference for other embedded devices equipped Texas Instruments chipsets.

Required Hardware

The hardware used for this step by step tutorial is:

Building a Linux Distribution with RAUC

RAUC, a robust and powerful open-source solution, demands advanced skills for initial integration. In general, to incorporate RAUC in a Yocto Project and OpenEmbedded image for BeagleBone Black the following actions have to be performed:

  • Use U-Boot as a bootloader
  • Enable SquashFS in the Linux kernel configuration
  • Use ext4 root file system
  • Design specific storage partitioning for the certain use case and configure RAUC accordingly
  • Provide a custom U-Boot script to properly switch between RAUC slots
  • Prepare a certificate and keyring to use for signing and verifying RAUC update bundles.

Leon Anavi has already done all these actions for core-image-minimal in Yocto/OpenEmbedded layer meta-rauc-community/meta-rauc-beaglebone. The layer is available at GitHub. Please follow the steps below to build core-image-minimal for BeagleBone Black with it:

  • Download the long term support (LTS) release Kirkstone reference Yocto distribution, Poky:
git clone -b kirkstone https://git.yoctoproject.org/poky poky-rauc-bbb
cd poky-rauc-bbb
  • Download the meta-rauc layer:
git clone -b kirkstone https://github.com/rauc/meta-rauc.git
  • Download meta-rauc-community layers, including meta-rauc-beaglebone:
git clone -b kirkstone https://github.com/rauc/meta-rauc-community.git
  • Download the meta-openembedded layer as it provides a recipe for nano which will be used for the demonstration:
git clone -b kirkstone git://git.openembedded.org/meta-openembedded

Initialize the build environment:

source oe-init-build-env
  • Include all layers in conf/bblayers.conf:
bitbake-layers add-layer ../meta-openembedded/meta-oe
bitbake-layers add-layer ../meta-rauc
bitbake-layers add-layer ../meta-rauc-community/meta-rauc-beaglebone
  • Adjust conf/local.conf by appending the following configurations to the end of the file:
MACHINE = "beaglebone-yocto"

# Use systemd as init manager
INIT_MANAGER = "systemd"

# Add RAUC to the image
IMAGE_INSTALL:append = " rauc"
DISTRO_FEATURES:append = " rauc"
  • Build a minimal bootable image:
bitbake core-image-minimal

The image creation process from scratch is time-consuming, encompassing various Yocto/OpenEmbedded recipes and configurations. Kindly await completion as bitbake diligently executes each tasks.

  • Flash tmp/deploy/images/beaglebone-yocto/core-image-minimal-beaglebone-yocto.wic.xz to microSD card.
  • Attach the USB-to-UART adapter to BeagleBone Black, plug the ethernet cable and the microSD card.

Press and hold button S2 while plugging in the 5V DC power supply to turn on BeagleBone Black and boot from microSD card.

BeagleBone black board has an onboard button labeled as S2. It is situated near the microSD card slot. Press and hold it while powering the board to boot from microSD card.

  • Verify that the system boots successfully, log in as user root without a password and check RAUC status:
rauc status

On the screenshot BeagleBone Black has been booted from RAUC slot rootfs.0 (A) on the microSD card.

NOTE: The meta-rauc-beaglebone layer includes a core-image-minimal.bbappend file, housing essential configurations for RAUC functionality. Apply these configurations similarly to other images intended for use in your embedded Linux device.

Creating a RAUC Update Bundle

RAUC update bundle comprises the file system image(s) or archive(s) designated for system installation, accompanied by a manifest detailing the images for installation, encompassing options and meta-information. Additionally, it may include scripts designated for execution before, during or after the installation process. To sign and verify the update bundles RAUC uses SSL keys. Layer meta-rauc-beaglebone contains a keyring containing all keys and a recipe for a simple RAUC update bundle for demonstration purposes only.

Follow the steps below to create RAUC update bundle that extends the system by adding the popular text based editor nano:

  • Add to conf/local.conf:
IMAGE_INSTALL:append = " nano"
  • Build the RAUC update bundle:
bitbake update-bundle

Following a successful execution, bitbake will produce the update-bundle-beaglebone-yocto.raucb file.

Updating BeagleBone Black with RAUC

Follow the steps below to update core-image-minimal running from a microSD card on BeagleBone Black:

  • Start a Python 3 web server on the build machine or another computer where the RAUC update bundle (aka update-bundle-beaglebone-yocto.raucb) is available and within the same network as BeagleBone Black, for example:
cd tmp/deploy/images/beaglebone-yocto/
pip3 install --user rangehttpserver
python3 -m RangeHTTPServer
  • On BeagleBone Black replace <IP> with the actual IP address of the computer on which the HTTP server is running and execute the following command to install the update:
rauc install http://<IP>:8000/update-bundle-beaglebone-yocto.raucb

The screenshot show successful installation of the RAUC updated bundle on BeagleBone Black.

  • Reboot BeagleBone Black to load the updated version:
reboot

NOTE: As alternative, instead of using an HTTP server, you can transfer the update bundle to BeagleBone Black and install it from local storage.

  • Verify that nano was added to the system:
which nano
  • Check RAUC status to confirm the system have booted from the second partition:
rauc status

On the screenshot, after sucessful installation of the RAUC update bundle, BeagleBone Black has been booted from RAUC slot rootfs.1 (B) on the microSD card. This slot contains nano.

In real-world product development, the Yocto Project and OpenEmbedded workflow can be enhanced with a few commands for easy implementation of continuous integration (CI).

From the dawn of OpenEmbedded and the Yocto Project, Konsulko engineers have been community contributors and guides for crafting commercial products. Our expertise spans RAUC, Mender, and various open-source solutions for top-notch software updates. Please get in touch with us to discuss how Konsulko engineers can help your own embedded product development.

Konsulko Group engineer to speak at Yocto Project Summit

Konsulko Group senior engineer Leon Anavi will be presenting at the Yocto Project Virtual Summit, Tuesday, November 28 through Thursday, November 30, 2023.

Formerly known as the Yocto Project Developer Day, the Summit has an expanded scope to include both workshops for engineers building customized Linux distributions and applications, as well as an open forum where maintainers, trainers and users present papers on how the project is evolving and how they are using it.

On Wednesday, November 29, Leon will present Integrating VNC in Weston with the Yocto Project and OpenEmbedded. Weston 12 introduces Virtual Network Computing (VNC) support, allowing remote connection and control through graphical desktop sharing.

Leon will examine the technical aspects — dependance on Neat VNC and AML libraries, TLS support and user authentication — followed by a step by step tutorial to demonstrate remote connection from another computer.

The presentation aims to simplify the process of setting up the VNC backend in Weston and empower developers to utilize this powerful feature seamlessly within their projects.

We hope you will join us for this presentation, and all of this new edition of Yocto Project Virtual Summit.

Using kernel config fragments to remove an unwanted feature

Adding a feature to a linux-yocto based kernel is fairly well documented. This makes sense because it is the most common thing you might want to do: “My board needs support for this sensor added to our BSP.”

Konsulko Group recently helped a customer that had exactly the opposite problem, a standard feature in linux-intel (which includes linux-yocto.inc and inherits the kernel-yocto class) needed to be removed. The SoC (in the Intel™ “Bay Trail” family) and the off-the-shelf industrial PC had a problem. When USB 3.0 (xHCI) support is enabled, the default BIOS settings (xHCI Mode = Auto) would cause the system to lock-up upon either warm reboot or shutdown. Given that these systems are deeply embedded in the field—where simply “hooking up a display, keyboard and mouse” is cost prohibitive—we needed to find an option that would not prevent OTA updates.

You might think you could apply a patch via SRC_URI to kmeta (yocto-kernel-cache), but this isn’t supported in the Yocto Project kernel tooling. Instead we can apply kernel config fragments that disable the problematic xHCI feature. The trade off is that USB 3.x devices won’t be able to run at full speed, but the systems in question have no need for USB 3.0 (they are a classic IoT gateway use case).

Determining your existing kernel configuration

The first thing you want to do in this situation is determine what your (default) kernel configuration is. In our case, Konsulko and our customer are using the ‘dunfell’ (3.1.x) branch of meta-intel with MACHINE="intel-corei7-64". Upon building an image or the kernel (e.g. bitbake virtual/kernel or bitbake linux-intel), the kernel configuration can be found at the following path:

<build>tmp/work/corei7-64-intel-common-poky-linux/linux-intel/5.4.170+gitAUTOINC+98cce1c95f_36f93ff941-r0/linux-corei7-64-intel-common-standard-build/.config

Where the kernel version is 5.4.170, the (shortened) git commit hash of the kernel cache is 98cce1c95f and the (shortened) git commit hash of the kernel source is 36f93ff941.

Modifying the kernel configuration with menuconfig

The documented way to modify the kernel configuration is with:

bitbake -c menuconfig linux-intel

This approach works fine, but you must remember to copy the resulting .config to defconfig in your recipe’s SRC_URI.

Alternatively you can create your kernel config fragments in the kernel build directory and then add them to your kernel recipe. The fragments can be created with the help of the diffconfig script in the kernel source tree.

Also note that you must have already run:

$ bitbake -c kernel_configme -f linux-intel

or previously built the kernel in order for the .config to be present.

Modifying the kernel configuration with devtool

It will come as no surprise that my preferred way to modify the kernel configuration is to run:

$ devtool menuconfig linux-intel

But you will get an error:

ERROR: No recipe named 'linux-intel' in your workspace

So first we must get the kernel recipe into our workspace:

$ devtool modify linux-intel

Now we are able to run:

$ devtool menuconfig linux-intel

One benefit of this approach is that devtool will run the required steps that need to happen before menuconfig can be run (most notably the do_kernel_configme task).

Determining the changes needed

Regardless of which method you used to run menuconfig, you will now be presented with the text UI:

Since Konsulko and our customer already knew we needed to change the xHCI enablement, we can quickly </> for Search and then enter xHCI.

This gives us several results, but the ones that we care about have [=y](built-in) next to them:

  1. CONFIG_USB_XHCI_HCD
  2. CONFIG_USB_XHCI_PCI
  3. CONFIG_USB_XHCI_PLATFORM

The top level item that needs to be disabled (set to N) is CONFIG_USB_XHCI_HCD:

After this we can spot check the other values are also disabled (by using </> for Search again):
CONFIG_USB_XHCI_PCI and CONFIG_USB_XHCI_PLATFORM:

Satisfied that we have the needed change, we can save our configuration. Press the <E> key or click on < Exit > to exit the sub-menus until you are at the top of the stack. Press the <S> key or click on < Save > to save the configuration. At they prompt, press enter or click on <Yes>.

Now, the benefit of the devtool workflow comes into play, because we are rewarded with:

INFO: Updating config fragment <build>/workspace/sources/linux-intel/oe-local-files/devtool-fragment.cfg

The contents of this file are what you might expect:

# CONFIG_USB_XHCI_HCD is not set

Applying our configuration change

If we don’t already have one, we need a layer into which to put our changes:

$ bitbake-layers create-layer ~/Projects/meta-awesome-bsp

Add the layer to our active layers:

$ bitbake-layers add-layer ~/Projects/meta-awesome-bsp

Create a directory–following the pattern in openembedded-core–for our kernel changes:

$ mkdir -p ~/Projects/meta-awesome-bsp/recipes-kernel/linux

Finish our recipe:

$ devtool finish linux-intel ~/Projects/meta-awesome-bsp

Examine the resulting directory structure:

$ tree ~/Projects/meta-awesome-bsp
/home/<user>/Projects/meta-awesome-bsp
├── conf
│&nbsp;&nbsp; └── layer.conf
├── COPYING.MIT
├── README
├── recipes-example
│&nbsp;&nbsp; └── example
│&nbsp;&nbsp;     └── example_0.1.bb
└── recipes-kernel
    └── linux
        ├── linux-intel
        │&nbsp;&nbsp; └── devtool-fragment.cfg
        └── linux-intel_%.bbappend

Since this might not be the only change to the kernel we will need to make, let us give the fragment a better name:

pushd ~/Projects/meta-awesome/recipes-kernel/linux/linux-intel
mv devtool-fragment.cfg disable-xhci-hcd.cfg

And create an .scc file to give the Yocto Project kernel tooling better hints of how to apply our change:

cat << EOF >> disable-xhci-hcd.scc
# SPDX-License-Identifier: MIT
define KFEATURE_DESCRIPTION "Disable options for xhci (USB 3.0)"
define KFEATURE_COMPATIBILITY board

kconf hardware disable-xhci-hcd.cfg
EOF

And finally make changes to our linux-intel_%.bbappend to reflect these files:

$ cd ..
$ cat linux-intel_%.bbappend
FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"

SRC_URI += "\
    file://disable-xhci-hcd.cfg \
    file://disable-xhci-hcd.scc \
"

Now—as long as our layer has high enough priority and no other recipes add kernel config fragments which conflict with our change—we should be able to build the kernel and inspect the resulting .config:

$ popd
$ bitbake linux-intel
$ grep -R XHCI tmp/work/corei7-64-intel-common-poky-linux/linux-intel/5.4.170+gitAUTOINC+98cce1c95f_36f93ff941-r0/linux-corei7-64-intel-common-standard-build/.config
# CONFIG_USB_XHCI_HCD is not set
# CONFIG_USB_ROLES_INTEL_XHCI is not set

We should also be able to run dmesg | grep xhci on the target and we would not expect to see any messages.

Summary

A Konsulko Group customer had a hardware problem that required us to remove a kernel feature. By using tools like devtool, we were able to fairly easily make a change to the kernel configuration and capture those changes in a persistent way with a .cfg fragment and a .bbappend. This approach solved the problem and allowed OTA updates to proceed to these deeply embedded devices in the field. Please contact us to discuss how Konsulko can help you with the unique requirements of your commercial project.

Building a DIY SOHO router, 18 months later

Building a DIY SOHO router using the Yocto Project build system OpenEmbedded, 18 months later

It’s been around a year since my last post on this project, and 18 months since I posted the article series itself. In the world of home networking equipment that’s practically a lifetime. So it’s worth doing a check-in on this project, I think.

My little router is still going just fine. In terms of things I had talked about earlier in the series, I’m still using the ability to easily roll back a test image to try out backports. Most recently, I tried to add IPv6 Prefix Delegation support to the DHCPv6 client in an older version of systemd. It didn’t work, but with just a reboot I was back to my normal image. As times change, devices at home change, and I’m using the dnsmasq configuration file to document what devices are in the house. Performance? Still doing just great. The next time I do one of these series, my household might have crossed the threshold where newer WiFi standards are in enough devices we own that I want something that handles them, but we aren’t there yet. By then I might also just have a new PCIe card to drop in.

In terms of the article series itself, it’s a testament to the stability of the Yocto Project and everyone who works on it. Since the original posts, Mender has internally upgraded a significant amount, and in turn some of the examples there aren’t quite correct for a modern build. Mender has excellent documentation, however, and it’s been easy to update my build to work all along the way and upgrade from the older version to the new. Everything else? Yes, that’s all still correct. What prompted this particular post is that the Yocto Project has announced another milestone release, and that’s always a good time to make sure my device is up to date. My latest changes were quite literally just renaming the Linux kernel bbappend file and saying the layer is compatible with the new release. That was less work than updating the firewall rules to take in to account both Daylight Savings Time changes and that my kids are a bit older and realistically want to be online a little later.

Using Rust with Yocto Project

by Paul Barker, Konsulko Group

Introduction

Rust is a modern programming language which emerged from Mozilla Research around 2010 and has been stable since 2015 (see the history section of the Wikipedia article). Rust is an excellent fit for embedded software development due to its focus on performance and safety without the overhead of garbage collection or a large language runtime. The zero-cost abstractions provided by Rust support developer productivity, allowing the use of traits, generics, functional programming styles and other high-level approaches in the knowledge that the resulting assembly code will perform just as well as more verbose, hand written lower level code.

Now is a great time to pick up Rust if you work in the Embedded space. The Rust Embedded Working Group has produced an Embedded Rust Book for an audience with existing embedded development knowledge and the Discovery Book for an audience with no embedded experience but a desire to learn. The Linux kernel community has began discussing the use of Rust within the kernel itself and the OpenEmbedded/Yocto Project community is planning to move Rust support into the openembedded-core layer during the next release cycle.

The benefits of Rust largely stem from the language’s memory model, the borrow checker and other features which will be new to most developers learning Rust. The above resources from the Rust Embedded WG along with several published books and online tutorials cover this material well and so it will not be repeated in detail here. However, if you wish to develop software in Rust for production deployment you should expect to invest at least a few weeks in learning the language, assuming existing familiarity with other programming languages like C, Python or Java.

This article will introduce a couple of simple example applications written in Rust, discuss how to compile and run these applications natively on a Linux system using the Cargo build system and show how to create Yocto Project recipes for these applications using the cargo-bitbake tool. Some basic knowledge of the Yocto Project is assumed but no previous experience of Rust should be required.

Getting Started with Rust

In this section we will install Rust on our Linux system and create two simple applications.

Note that it is not necessary to have Rust installed natively in order to build applications and libraries written in Rust under bitbake. However, installing Rust natively does allow us to develop, test and debug applications on the host before we try to cross-compile them and it is an important step to take when learning Rust.

Installing Rust

The recommended way of installing Rust on a Linux system is to download and run the official installation script. When prompted with the installation options it is usually sufficient to select option 1 to use the defaults. This will install Rust in the current user’s home directory and modify the profile files to set necessary environment variables at login.

$ curl https://sh.rustup.rs -sSf | sh

    <output snipped>

Current installation options:


   default host triple: x86_64-unknown-linux-gnu
     default toolchain: stable (default)
               profile: default
  modify PATH variable: yes

1) Proceed with installation (default)
2) Customize installation
3) Cancel installation
>1

    <output snipped>

Rust is installed now. Great!

To get started you need Cargo's bin directory ($HOME/.cargo/bin) in your PATH
environment variable. Next time you log in this will be done
automatically.

To configure your current shell run source $HOME/.cargo/env

After installing Rust you should log out and log back in to ensure that environment variables are set correctly.

Hello, World

As is traditional, we will begin by looking at a “Hello, World” application.

Each Rust application or library should have its own project directory. Within this directory, the source code is usually placed in a src directory and the top level directory contains the Cargo config file for the project
and any other collateral files such as a README file, LICENSE file, etc.

To create our project directory and populate it with initial files we can use the cargo init command:

$ cargo init hello-rs
     Created binary (application) package

Within our new hello-rs directory, this command creates an initial source file in src/main.rs with the following contents:

fn main() {
    println!("Hello, world!");
}

This makes our job of writing a Hello World application very simple – no code modifications are needed!

The cargo init command also creates a Cargo.toml file in our project directory to store project configuration and metadata:

[package]
name = "hello-rs"
version = "0.1.0"
authors = ["Paul Barker <[email protected]>"]
edition = "2018"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]

We should test our new Hello World application natively before we try to cross-compile it under bitbake. To do this we can use the cargo build and cargo run commands:

$ cargo build
   Compiling hello v0.1.0 (/home/pbarker/Projects/Rust/rust/hello-rs)
    Finished dev [unoptimized + debuginfo] target(s) in 0.29s
$ cargo run
    Finished dev [unoptimized + debuginfo] target(s) in 0.01s
     Running `target/debug/hello-rs`
Hello, world!

The last stage for our hello world application is to publish it as a git repository so that it can be fetched and built in our Yocto Project environment. We should create a LICENSE file and a README file in the top level of the project for the benefit of anyone who wants to reuse our code. My preference is for the Apache license version 2.0 but feel free to use any appropriate open source license here.

We should also add some extra metadata to the Cargo.toml file to specify the license, briefly describe the project and link to the location where we will be publishing the repository. This metadata will be used by cargo-bitbake when we generate a recipe for our application. In my case the repository will be published to my GitLab account.

--- a/Cargo.toml
+++ b/Cargo.toml
@@ -3,6 +3,9 @@ name = "hello-rs"
 version = "0.1.0"
 authors = ["Paul Barker <[email protected]>"]
 edition = "2018"
+license = "Apache-2.0"
+description = "Hello World application"
+repository = "https://gitlab.com/pbarker.dev/rust/hello-rs.git"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

To finish up, commit the project files to a git repository and push to a location which can be reached when building using Yocto Project. Alternatively, you can make use of the hello-rs repository I published under my GitLab account.

The Hello World application above will demonstrate only part of the capabilities of the cargo-bitbake tool and the Rust support in Yocto Project. To see how Rust dependencies are handled in Yocto Project we’ll need an application which actually depends on a Rust library (known as a crate). The print-rand application will fill this role as it uses the rand crate to generate random numbers.

As before we will start by creating the project using cargo init:

$ cargo init print-rand
     Created binary (application) package

We will now modify the src/main.rs file to generate and print a random number:

use rand::prelude::*;

fn main() {
    let x: u32 = random();
    println!("x = {}", x);
}

We will also modify the Cargo.toml file to list the rand crate as a dependency:

[package]
name = "print-rand"
version = "0.1.0"
authors = ["Paul Barker <[email protected]>"]
edition = "2018"

[dependencies]
rand = "0.7"

We can build and test this application in a similar way to the previous Hello World app. Note that each dependency is downloaded and built along the way:

$ cargo build
   Compiling libc v0.2.77
   Compiling getrandom v0.1.15
   Compiling cfg-if v0.1.10
   Compiling ppv-lite86 v0.2.9
   Compiling rand_core v0.5.1
   Compiling rand_chacha v0.2.2
   Compiling rand v0.7.3
   Compiling print-rand v0.1.0 (/home/pbarker/Projects/Rust/rust/print-rand)
    Finished dev [unoptimized + debuginfo] target(s) in 3.60s
$ cargo run
    Finished dev [unoptimized + debuginfo] target(s) in 0.01s
     Running `target/debug/print-rand`
x = 643356417

As before, we should add LICENSE and README files at this stage and extend the metadata in the Cargo.toml file:

--- a/Cargo.toml
+++ b/Cargo.toml
@@ -3,6 +3,9 @@ name = "print-rand"
 version = "0.1.0"
 authors = ["Paul Barker <[email protected]>"]
 edition = "2018"
+license = "Apache-2.0"
+description = "Print a random number"
+repository = "https://gitlab.com/pbarker.dev/rust/print-rand.git"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

Lastly, commit the project files to a git repository and push to a public location. As before you may alternatively make use of the print-rand repository I published under my GitLab account.

Using cargo-bitbake

Now that we have created a couple of simple Rust applications and published them we can look at creating bitbake recipes using the cargo-bitbake tool. The first step of this process is to install the tool itself:

$ cargo install cargo-bitbake

    <output snipped>

   Compiling cargo-bitbake v0.3.14
    Finished release [optimized] target(s) in 12m 30s
  Installing /home/debian/.cargo/bin/cargo-bitbake
   Installed package `cargo-bitbake v0.3.14` (executable `cargo-bitbake`)

Before we run cargo bitbake for each our projects we should ensure that all changes are committed and pushed to the remote repository. We should also check the remote URL for each repository as this will be used to set SRC_URI. If the remote URL uses SSH access then you should ensure that this can be reached using an SSH key from the Yocto build environment or switch to HTTPS access.

Once we’re happy with the state of our repository we can run cargo bitbake in the top directory of our hello-rs project (note that we use a space not a dash in the command here):

$ cargo bitbake
No package.homepage set in your Cargo.toml, trying package.repository
Wrote: hello_0.1.0.bb

The message printed by cargo bitbake indicates that the repository entry in our Cargo.toml file was used as the homepage URL since we did not specify a separate homepage.

We can now look at the generated recipe file hello-rs_0.1.0.bb:

# Auto-Generated by cargo-bitbake 0.3.14
#
inherit cargo

# If this is git based prefer versioned ones if they exist
# DEFAULT_PREFERENCE = "-1"

# how to get hello-rs could be as easy as but default to a git checkout:
# SRC_URI += "crate://crates.io/hello-rs/0.1.0"
SRC_URI += "git://gitlab.com/pbarker.dev/rust/hello-rs.git;protocol=https;nobranch=1;branch=dev"
SRCREV = "cec42fb0d147e4a4b271256c475620ff627c8856"
S = "${WORKDIR}/git"
CARGO_SRC_DIR = ""


# please note if you have entries that do not begin with crate://
# you must change them to how that package can be fetched
SRC_URI += " \
"



# FIXME: update generateme with the real MD5 of the license file
LIC_FILES_CHKSUM = " \
    file://LICENSE;md5=86d3f3a95c324c9479bd8986968f4327 \
"

SUMMARY = "Hello World application"
HOMEPAGE = "https://gitlab.com/pbarker.dev/rust/hello-rs.git"
LICENSE = "Apache-2.0"

# includes this file if it exists but does not fail
# this is useful for anything you may want to override from
# what cargo-bitbake generates.
include hello-rs-${PV}.inc
include hello-rs.inc

As we noted above, the SRC_URI and SRCREV entries are based on the remote URI and the currently checked out commit of our local git repository. The SUMMARYHOMEPAGE and LICENSE entries are based on the metadata in our Cargo.toml file. The LIC_FILES_CHKSUM entry is set based on the LICENSE file in our project.

We can also generate a recipe for the print-rand project by running cargo bitbake in the top directory of this project:

$ cargo bitbake
No package.homepage set in your Cargo.toml, trying package.repository
Wrote: print-rand_0.1.0.bb

The print-rand_0.1.0.bb recipe is very similar to the previous recipe for our hello world application. The SRC_URISRCREVSUMMARY and HOMEPAGE are changed to the appropriate values for this project. The SRC_URI variable is extended with a list of the dependency crates required by this project, this includes not just the rand crate that we explicitly listed as a dependency in our Cargo.toml file but also all the recursive dependencies of this crate.

# Auto-Generated by cargo-bitbake 0.3.14
#
inherit cargo

# If this is git based prefer versioned ones if they exist
# DEFAULT_PREFERENCE = "-1"

# how to get print-rand could be as easy as but default to a git checkout:
# SRC_URI += "crate://crates.io/print-rand/0.1.0"
SRC_URI += "git://gitlab.com/pbarker.dev/rust/print-rand.git;protocol=https;nobranch=1;branch=dev"
SRCREV = "3397247f929f28d70adbb65d3990dc72699553bb"
S = "${WORKDIR}/git"
CARGO_SRC_DIR = ""


# please note if you have entries that do not begin with crate://
# you must change them to how that package can be fetched
SRC_URI += " \
    crate://crates.io/cfg-if/0.1.10 \
    crate://crates.io/getrandom/0.1.15 \
    crate://crates.io/libc/0.2.79 \
    crate://crates.io/ppv-lite86/0.2.9 \
    crate://crates.io/rand/0.7.3 \
    crate://crates.io/rand_chacha/0.2.2 \
    crate://crates.io/rand_core/0.5.1 \
    crate://crates.io/rand_hc/0.2.0 \
    crate://crates.io/wasi/0.9.0+wasi-snapshot-preview1 \
"



# FIXME: update generateme with the real MD5 of the license file
LIC_FILES_CHKSUM = " \
    file://LICENSE;md5=86d3f3a95c324c9479bd8986968f4327 \
"

SUMMARY = "Print a random number"
HOMEPAGE = "https://gitlab.com/pbarker.dev/rust/print-rand.git"
LICENSE = "Apache-2.0"

# includes this file if it exists but does not fail
# this is useful for anything you may want to override from
# what cargo-bitbake generates.
include print-rand-${PV}.inc
include print-rand.inc

We can now add these recipes to a Yocto Project layer and build them using bitbake. Support for the Rust toolchain in Yocto Project is provided by the meta-rust layer so this layer must be included before these recipes can be built. As there are many ways to put together a Yocto Project build we won’t cover this in this blog post. However, you can see a walkthrough of this process in the Using Rust with Yocto Project demo presented at theYocto Project Summit Europe 2020.

Helping Yocto Project work with Python 3

According to the statistics from StackOverflow Python is the fastest-growing major programming language. First released in 1991, Python is nowadays commonly used for various applications in multiple different industries. Python is a first class citizen of many embedded Linux systems.

The Yocto Project, a collaborative project of the Linux Foundation for creating custom Linux distributions for embedded devices, uses the OpenEmbedded build system and relies on layer meta-python from meta-openembedded to deliver Python 3 packages. Until recently, meta-python was providing both python 2 and python 3 versions of each package. The Python community decided that January 1, 2020, was the day to sunset Python 2. Since then Python 2 has been officially deprecated. This triggered major changes related to the support in Yocto and OpenEmbedded. All recipes for version 2 were moved to layer meta-python2 to provide legacy support after the end of life for this Python release. In meta-openembedded/meta-python, the OpenEmbedded community started efforts to remove all recipes for version 2 as well as to consolidate inc and bb files into a single bb file for version 3.

Konsulko Group engineers are regular contributors to various upstream open source projects, including meta-openembedded and more specifically to meta-python. In the past month, Leon Anavi joined the community efforts for consolidating Python 3 recipes in a single file as well as for upgrading various packages. Nowadays, most of the Python 3 recipes are utilizing the pypi bbclass which takes care for downloading and processing packages from pypi.org. This makes most of the upgrades to new releases of a Python package straight-forward. However, it is important to check the list of build and runtime dependencies as well as to ensure that bitbake still works fine with the upgraded recipe version for both x86-64 and ARM architectures prior to submission. 

Let’s have a closer look at the recipe python3-protobuf. It has been recently upgraded from version 3.11.3 to version 3.12.2. Protocol Buffers, also known as protobuf, are Google’s language-neutral, platform-neutral, extensible mechanism for serializing structured data. In the Yocto and OpenEmbedded ecosystem, recipe python3-protobuf depends on recipe protobuf from layer meta-oe. Both meta-oe and meta-python are part of meta-openembedded. So to avoid version mismatch and to ensure that bitbake will be able to successfully build python3-protobuf version 3.12.2 an upgrade of recipe protofobuf to the same version was mandatory. We contributed both upgrades to the master branch of the git repository meta-openembedded. The maintainers took care of cherry-picking them to the dunfell branch which is compatible with the latest stable release of the Yocto Project as of the moment. As a result, if you checkout the latest stable release of Poky, the reference system of the Yocto Project, and meta-openembedded you will be able to quickly build the latest version of protobuf and python3-protobuf out of the box.

Konsulko engineers have been there since the earliest days of the OpenEmbedded build framework and the Yocto Project. We continue to regularly make upstream contributions to these open source projects. Please contact us if you need your “own” Linux distro for your own embedded product.