If you don’t already have a Yocto project that you want to add OTA to, you can use the HERE OTA Connect Quickstart project to rapidly get up and running on a Raspberry Pi. It takes a standard poky distribution, and adds OTA and OSTree capabilities.

If you already have a Yocto-based project and you want to add atomic filesystem updates to it, you just need to do three things:

1. Clone the meta-updater layer and add it to your bblayers.conf.

2. Clone BSP integration layer (meta-updater-${PLATFORM}, e.g. meta-updater-raspberrypi) and add it to your conf/bblayers.conf. If your board isn’t supported yet, you could write a BSP integration for it yourself. See the Adding support for your board section for the details.

3. Set up your distro. If you are using "poky", the default distro in Yocto, you can change it in your conf/local.conf to "poky-sota". Alternatively, if you are using your own or third party distro configuration, you can add INHERIT += " sota" to it, thus combining capabilities of your distro with meta-updater features.

You can then build your image as usual, with bitbake. After building the root file system, bitbake will then create an OSTree-enabled version of it, commit it to your local OSTree repo and (optionally) push it to a remote server. Additionally, a live disk image will be created (normally named ${IMAGE_NAME}.-sdimg-ota e.g. core-image-raspberrypi3.rpi-sdimg-ota). You can control this behaviour through variables in your local.conf.

With AGL you can just add agl-sota feature while configuring your build environment:

You can then run:

and get as a result an ostree_repo folder in your images directory (tmp/deploy/images/${MACHINE}/ostree_repo). It will contain:

• your OSTree repository, with the rootfs committed as an OSTree deployment,

• an ota-ext4 bootstrap image, which is an OSTree physical sysroot as a burnable filesystem image, and optionally

• some machine-dependent live images (e.g. .wic for Raspberry Pi or .porter-sdimg-ota Renesas Porter board).

Although aglsetup.sh hooks provide reasonable defaults for SOTA-related variables, you may want to tune some of them.

Ubuntu users that encounter an error due to missing Python.h should install libpython2.7-dev on their host machine.

If your board isn’t supported yet, you can add board integration code yourself. The main purpose of this code is to provide a bootloader that will be able to use OSTree’s boot directory. In the meta-updater integration layers we have written so far, the basic steps are:

1. Make the board boot into U-Boot

2. Make U-boot import variables from /boot/loader/uEnv.txt and load the kernel with initramfs and kernel command line arguments according to what is set in this file.

You may take a look into Minnowboard or Raspberry Pi integration layers for examples.

Although we have used U-Boot so far, other boot loaders can be configured work with OSTree as well.

Your images will also need network connectivity to be able to reach an actual OTA backend. Our 'poky-sota' distribution does not mandate or install a default network manager but our supported platforms use the virtual/network-configuration recipe, which can be used as a starting example.

OSTree used to include a simple HTTP server as part of the ostree binary, but this has been removed in more recent versions. However, OSTree repositories are self-contained directories, and can be trivially served over the network using any HTTP server. For example, you could use Python’s SimpleHTTPServer:

You can then run ostree from inside your device by adding your repo:

After restarting, you will boot into the newly deployed OS image.

For example, on the raspberry pi you can try this sequence:

The aktualizr repo contains a tool, garage-push, which lets you push the changes in OSTree repository generated by bitbake process. It communicates with an http server capable of querying files with HEAD requests and uploading them with POST requests. In particular, this can be used with HERE OTA Connect. garage-push is used as follows:

You can set SOTA_PACKED_CREDENTIALS in your local.conf to automatically synchronize your build results with a remote server. Credentials are stored in an archive as described in the aktualizr documentation.

Aktualizr supports a variety of configuration options via a configuration file and the command line. There are two primary ways to control aktualizr’s configuration from meta-updater.

First, you can set SOTA_CLIENT_PROV to control which provisioning recipe is used. Each recipe installs an appropriate sota.toml file from aktualizr according to the provisioning needs. See the SOTA-related variables in local.conf section for more information.

Second, you can write recipes to install additional config files with customized options. A few recipes already exist to address common needs and provide an example:

• aktualizr-auto-reboot.bb configures aktualizr to automatically reboot after new updates are installed in order to apply the updates immediately. This is only relevant for package managers (such as OSTree) that require a reboot to complete the installation process. If this is not enabled, you will need to reboot the system through other means.

• aktualizr-disable-send-ip.bb disables the reporting of networking information to the server. This is enabled by default and supported by HERE OTA Connect. However, if you are using a different server that does not support this feature, you may want to disable it in aktualizr.

• aktualizr-log-debug.bb sets the log level of aktualizr to 0 (trace). The default is 2 (info). This recipe is intended for development and debugging purposes.

To use these recipes, you will need to add them to your image with a line such as IMAGE_INSTALL_append = " aktualizr-log-debug " in your local.conf.

With systemd based images, it is possible to set resource policies for the aktualizr service. The main use case is to provide a safeguard against resource exhaustion during an unforeseen failure scenario.

To enable it, install aktualizr-resource-control on the target image and optionally override the default resource limits set in aktualizr_git.bb, from your local.conf.

For example:

Warning: overriding target version is a dangerous operation, make sure you understand this section completely before doing it.

Every time you build an image with SOTA_PACKED_CREDENTIALS set, a new entry in your Uptane metadata is created and you can see it in the OTA Garage UI if you’re using one. Normally this version will be equal to OSTree hash of your root file system. If you want it to be different though you can override is using one of two methods:

1. Set GARAGE_TARGET_VERSION variable in your local.conf.

2. Write a recipe or a bbclass to write the desired version to ${STAGING_DATADIR_NATIVE}/target_version. An example of such bbclass can be found in classes/target_version_example.bbclass.

Please note that [target name, target version] pairs are expected to be unique in the system. If you build a new target with the same target version as a previously built one, the old package will be overwritten on the update server. It can have unpredictable effect on devices that have this version installed, and it is not guaranteed that information will be reported correctly for such devices or that you will be able to update them (we’re doing our best though). The easiest way to avoid problems is to make sure that your overriding version is as unique as an OSTree commit hash.