Delta update support

You have access to robust delta updates if you are using Mender Professional or Mender Enterprise. This section describes how to enable delta updates on your devices by installing the mender-binary-delta Update Module with your Yocto Project build.

Once your devices support installing delta updates, see Create a Delta update Artifact for a tutorial on creating a delta update from two Operating System updates.

Prerequisites

To use delta update, you must be using a read-only root filesystem. There are several ways of achieving this, which is out of this tutorial's scope. Generally speaking, ensure the bootloader and the /etc/fstab don't contain any rw reference.

You will need the binaries from the downloaded content both on the host and the device. More information on where to place every file in the sections below.

For additional troubleshooting, you can check the Delta updates troubleshooting guide.

Download

Download the mender-binary-delta binaries following the instructions.

Integrate mender-binary-delta into your image

Delta updates require the mender-binary-delta Update Module and the configuration file (mender-binary-delta.conf) on the device side. The steps on how to achieve this will depend on the way you're generating the image. We'll present only the location where you need to place the files.

Copy the mender-binary-delta binary into /usr/share/mender/modules/v3/ on your device from the content you downloaded in the previous step. Please ensure you're copying the binary from the directory specifying your architecture.

The mender-binary-delta.conf is a configuration on the device telling the update module the location of A/B partitions. It must be generated and placed in /etc/mender/mender-binary-delta.conf.

The content of the mender-binary-delta.conf configuration file is case-dependent. Below is an example of how it might look, but you might need different /dev/* locations depending on your device's name:

{
  "RootfsPartA": "/dev/mmcblk0p2",
  "RootfsPartB": "/dev/mmcblk0p3"
}

Next steps

For information on creating Delta update Artifacts, see Create a Delta update Artifact.

For more information about delta updates, including how to deploy them, as well as troubleshooting, see the Mender Hub page about mender-binary-delta.