Building a Mender Yocto Project image

This document outlines the steps needed to build a Yocto Project image for a device. The build output will most notably include:

  • a file that can be flashed to the device storage during initial provisioning, it has suffix .sdimg
  • an Artifact containing rootfs filesystem image file that Mender can deploy to your provisioned device, it has suffix .mender

If you do not want to build your own images for testing purposes, the Getting started tutorials provide links to several demo images.

What is meta-mender?

meta-mender is a set of layers that enable the creation of a Yocto Project image where the Mender client is part of the image. With Mender installed and configured on the image, you can deploy image updates and benefit from features like automatic roll-back, remote management, logging and reporting.

Inside meta-mender there are several layers. The most important one is meta-mender-core, which is required by all builds that use Mender. meta-mender-core takes care of:

Each one of these steps can be configured further, see the linked sections for more details.

The other layers in meta-mender provide support for specific boards.

For general information about getting started with Yocto Project, it is recommended to read the Yocto Project Quick Start guide.

Prerequisites

Device integrated with Mender

Before building for your device with Mender, Mender needs to be integrated with your device (most notably with U-Boot). This integration enables robust and atomic rollbacks with Mender. The following reference devices are already integrated with Mender, so if you are building for one of these you do not need to do any integration:

If you are building for a different device, please see Device integration for general requirements and adjustments you might need to enable your device to support atomic image-based deployments with rollback. There might already be similar devices you can use as a starting point in the meta-mender repository.

If you want to save time, you can use our professional services to integrate your device with Mender.

Correct clock on device

Make sure that the clock is set correctly on your devices. Otherwise certificate verification will become unreliable and the Mender client can likely not connect to the Mender server. See certificate troubleshooting for more information.

Yocto Project

We use the pyro branch of the Yocto Project and meta-mender below. Building meta-mender on other releases of the Yocto Project will likely not work seamlessly. meta-mender also has other branches like daisy that correspond to Yocto Project releases, but these branches are no longer maintained by Mender developers. We offer professional services to to implement and support other branches over time, please take a look at the Mender professional services offering.

A Yocto Project poky environment is required. If you already have this in your build environment, please open a terminal, go to the poky directory and skip to Adding the meta layers.

On the other hand, if you want to start from a clean Yocto Project environment, you need to clone the latest poky and go into the directory:

git clone -b pyro git://git.yoctoproject.org/poky
cd poky

Note that the Yocto Project also depends on some development tools to be in place.

Adding the meta layers

We will now add the required meta layers to our build environment. Please make sure you are standing in the directory where poky resides, i.e. the top level of the Yocto Project build tree, and run these commands:

git clone -b pyro git://github.com/mendersoftware/meta-mender

Next, we initialize the build environment:

source oe-init-build-env

This creates a build directory with the default name, build, and makes it the current working directory.

We then need to add the Mender layers into our project:

bitbake-layers add-layer ../meta-mender/meta-mender-core

The meta-mender-demo layer (below) is not appropriate if you are building for production devices. Please go to the section about building for production to see the difference between demo builds and production builds.

bitbake-layers add-layer ../meta-mender/meta-mender-demo

Finally, add the Mender layer specific to your board. Mender currently comes with three reference devices that you can build for (only add one of these):

  • Raspberry Pi 3 (other revisions might also work): bitbake-layers add-layer ../meta-mender/meta-mender-raspberrypi (depends on meta-raspberrypi)
  • BeagleBone Black: bitbake-layers add-layer ../meta-mender/meta-mender-beaglebone
  • Virtual device: bitbake-layers add-layer ../meta-mender/meta-mender-qemu

Other devices may have community support, either in meta-mender or other repositories. If you are building for a different device, please see Device integration for general requirements and adjustments you might need to enable your device to support Mender.

At this point, all the layers required for Mender should be part of your Yocto Project build environment.

Configuring the build

The configuration in conf/local.conf below will create a build that runs the Mender client in managed mode, as a systemd service. It is also possible to run Mender standalone from the command-line or a custom script. See the section on customizations for steps to disable the systemd integration.

Add these lines to the start of your conf/local.conf:

# The name of the disk image and Artifact that will be built.
# This is what the device will report that it is running, and different updates must have different names
# because Mender will skip installation of an Artifact if it is already installed.
MENDER_ARTIFACT_NAME = "release-1"

INHERIT += "mender-full"

# A MACHINE integrated with Mender.
# raspberrypi3, beaglebone, and vexpress-qemu are reference devices
MACHINE = "<YOUR-MACHINE>"

# For Rasberry Pi, uncomment the following block:
# RPI_USE_U_BOOT = "1"
# MENDER_PARTITION_ALIGNMENT_KB = "4096"
# MENDER_BOOT_PART_SIZE_MB = "40"
# IMAGE_INSTALL_append = " kernel-image kernel-devicetree"
# IMAGE_FSTYPES_remove += " rpi-sdimg"

# The version of Mender to build. This needs to match an existing recipe in the meta-mender repository.
#
# Given your Yocto Project version, see which versions of Mender you can currently build here:
# https://docs.mender.io/architecture/compatibility#mender-client-and-yocto-project-version
#
# Given a Mender client version, see the corresponding version of the mender-artifact utility:
# https://docs.mender.io/architecture/compatibility#mender-client-and-artifact-format
#
# Note that by default this will select the latest released version of the tools.
# If you need an earlier version, please uncomment the following and set to the
# required version.
#
# PREFERRED_VERSION_pn-mender = "1.2.%"
# PREFERRED_VERSION_pn-mender-artifact = "2.1.%"
# PREFERRED_VERSION_pn-mender-artifact-native = "2.1.%"

# Build for Hosted Mender
# To get your tenant token, log in to https://hosted.mender.io,
# click your email at the top right and then "My organization".
# Remember to remove the meta-mender-demo layer (if you have added it).
# We recommend Mender 1.2.1 and Yocto Project's pyro or later for Hosted Mender.
#
# MENDER_SERVER_URL = "https://hosted.mender.io"
# MENDER_TENANT_TOKEN = "<YOUR-HOSTED-MENDER-TENANT-TOKEN>"

DISTRO_FEATURES_append = " systemd"
VIRTUAL-RUNTIME_init_manager = "systemd"
DISTRO_FEATURES_BACKFILL_CONSIDERED = "sysvinit"
VIRTUAL-RUNTIME_initscripts = ""

IMAGE_FSTYPES = "ext4"

The size of the disk image (.sdimg) should match the total size of your storage so you do not leave unused space; see the variable MENDER_STORAGE_TOTAL_SIZE_MB for more information. Mender automatically selects the file system types it builds into the disk image, which is used for initial flash provisioning, based on the IMAGE_FSTYPES variable. See the section on file system types for more information.

It is suggested to add INHERIT += "rm_work" to conf/local.conf in order to conserve disk space during the build.

Building the image

Once all the configuration steps are done, build an image with bitbake:

bitbake <YOUR-TARGET>

Replace <YOUR-TARGET> with the desired target or image name, e.g. core-image-full-cmdline.

The first time you build a Yocto Project image, the build process can take several hours. The successive builds will only take a few minutes, so please be patient this first time.

Using the build output

After a successful build, the images and build artifacts are placed in tmp/deploy/images/<YOUR-MACHINE>/.

The files with suffix .sdimg are used to provision the device storage for devices without Mender running already. Please proceed to Provisioning a new device for steps to do this.

On the other hand, if you already have Mender running on your device and want to deploy a rootfs update using this build, you should use the Mender Artifact files, which have .mender suffix. You can either deploy this Artifact in managed mode with the Mender server as described in Deploy to physical devices or by using the Mender client only in Standalone deployments.

If you built for the virtual Mender reference device (vexpress-qemu), you can start up your newly built image with the script in ../meta-mender/meta-mender-qemu/scripts/mender-qemu and log in as root without password.