Android devices in the field can receive and install over-the-air (OTA) updates to the system and application software. OTA updates are designed to upgrade the underlying operating system and the read-only applications installed on the system partition. These updates do not affect applications installed by the user.

Devices have a special recovery partition with the software needed to unpack a downloaded update package and apply it to the rest of the system.

OTA update packages

Android release tools can build two types of update packages:

  • A full update package contains the entire final state of the device (system, boot, vendor, and recovery partitions).

    See Create a full update package.

    • This update package size is bigger.

    • The package can install the new version regardless of the current state of the device.

  • An incremental update package contains several binary patches generated from the difference between an old build and the new one.

    See Create an incremental update package.

    • Since these patches are applied to the data already on the device, the update packages may be smaller.

    • You can only install an incremental update on devices running the old build used when the incremental update package was constructed.

    • To generate an incremental package, you must use the release tools and the two build versions, the previous build (the one you want to update from) and the new one (the one you want to update to). This means you must keep the previous build version.

The python tool ota_from_target_files (at build/tools/releasetools) can build full and incremental packages. The tool takes the target_files zip file as input:

  • One target_files zip to generate a full update package.

  • Two target_files zips (old and new versions) to generate an incremental update package. The tool compares new target_files zip with the one from last release, and generates binary differences in the incremental package.

Create a full update package

To build a full update package for your platform based on Digi’s source code, follow these steps:

  1. You must have created the signed-target_files zip (see Sign for release).

  2. Change to the directory where the source code is installed.

    $ cd dea-9.0-r3

  3. Run the following command:

    $ ./build/tools/releasetools/ota_from_target_files \
  -k ~/android-certs/releasekey \
  out/dist/signed-target-files.zip \
  out/dist/full-ota-update.zip

The file out/dist/full-ota-update.zip is the update package to be installed in your ConnectCore 8X.

To install the update package out/dist/full-ota-update.zip in your ConnectCore 8X, follow the steps in Update Android with OTA packages.
To establish a secure environment where the access to the private key is restricted, see Release in a secure environment.

Create an incremental update package

To build an incremental update package, use the ota_from_target_files tool with the target_files zip files of the old version (the one you want to update from) and the new one (the one you want to update to).

For example, to generate an incremental package to update from version A to version B:

  1. You must have created the signed-target_files zip for version A, A-signed-target_files.zip and version B, B-signed-target_files.zip. See Sign for release.

  2. Change to the directory where the source code is installed.

    $ cd dea-9.0-r3

  3. Run the following command:

    $ ./build/tools/releasetools/ota_from_target_files \
  -k ~/android-certs/releasekey \
  -i A-signed-target_files.zip B-signed-target_files.zip \
  A_to_B-incremental-ota-update.zip
To install the update package A_to_B-incremental-ota-update.zip in your ConnectCore 8X, follow the steps in Update Android with OTA packages.

The incremental package is only applicable to devices running exactly the same previous build used as the incremental package’s starting point. In this example, the A_to_B-incremental-ota-update.zip can only be installed on a device that has A version.

To establish a secure environment where the access to the private key is restricted, see Release in a secure environment.

Update package with wipe data support

The ota_from_target_files tool includes several options for the generation of ota update packages. One of them is the possibility to wipe the user data partition when an ota package is installed.

Use the --wipe_user_data option of this tool to create an update package with wipe data partition support:

$ ./build/tools/releasetools/ota_from_target_files \
  --wipe_user_data out/dist/signed-target_files.zip \
  out/dist/full-ota-update-wipe_data.zip
For more information about OTA updates, see https://source.android.com/devices/tech/ota.