platform_bootable_recovery/updater_sample

SystemUpdaterSample

This app demonstrates how to use Android system updates APIs to install OTA updates. It contains a sample client for update_engine to install A/B (seamless) updates and a sample of applying non-A/B updates using recovery.

A/B (seamless) update is available since Android Nougat (API 24), but this sample targets the latest android.

Workflow

SystemUpdaterSample app shows list of available updates on the UI. User is allowed to select an update and apply it to the device. App shows installation progress, logs can be found in adb logcat. User can stop or reset an update. Resetting the update requests update engine to cancel any ongoing update, and revert if the update has been applied. Stopping does not revert the applied update.

Update Config file

In this sample updates are defined in JSON update config files. The structure of a config file is defined in com.example.android.systemupdatersample.UpdateConfig, example file is located at res/raw/sample.json.

In real-life update system the config files expected to be served from a server to the app, but in this sample, the config files are stored on the device. The directory can be found in logs or on the UI. In most cases it should be located at /data/user/0/com.example.android.systemupdatersample/files/configs/.

SystemUpdaterSample app downloads OTA package from url. In this sample app url is expected to point to file system, e.g. file:///data/sample-builds/ota-002.zip.

If ab_install_type is NON_STREAMING then app checks if url starts with file:// and passes url to the update_engine.

If ab_install_type is STREAMING, app downloads only the entries in need, as opposed to the entire package, to initiate a streaming update. The payload.bin entry, which takes up the majority of the space in an OTA package, will be streamed by update_engine directly. The ZIP entries in such a package need to be saved uncompressed (ZIP_STORED), so that their data can be downloaded directly with the offset and length. As payload.bin itself is already in compressed format, the size penalty is marginal.

if ab_config.force_switch_slot set true device will boot to the updated partition on next reboot; otherwise button "Switch Slot" will become active, and user can manually set updated partition as the active slot.

Config files can be generated using tools/gen_update_config.py. Running ./tools/gen_update_config.py --help shows usage of the script.

Running on a device

The commands expected to be run from $ANDROID_BUILD_TOP and for demo purpose only.

1. Compile the app $ mmma bootable/recovery/updater_sample.
2. Install the app to the device using $ adb install <APK_PATH>.
3. Change permissions on /data/ota_package/ to 0777 on the device.
4. Set SELinux mode to permissive. See instructions below.
5. Add update config files.
6. Push OTA packages to the device.

Sending HTTP headers from UpdateEngine

Sometimes OTA package server might require some HTTP headers to be present, e.g. Authorization header to contain valid auth token. While performing streaming update, UpdateEngine allows passing on certain HTTP headers; as of writing this sample app, these headers are Authorization and User-Agent.

android.os.UpdateEngine#applyPayload contains information on which HTTP headers are supported.

Development

• Create a UI with list of configs, current version, control buttons, progress bar and log viewer
• Add PayloadSpec and PayloadSpecs for working with update zip file
• Add UpdateConfig for working with json config files
• Add applying non-streaming update
• Prepare streaming update (partially downloading package)
• Add applying streaming update
• Add stop/reset the update
• Add demo for passing HTTP headers to UpdateEngine#applyPayload
• Package compatibility check
• Deferred switch slot demo
• Add tests for MainActivity
• Verify system partition checksum for package
• Add non-A/B updates demo

Running tests

1. Build $ mmma bootable/recovery/updater_sample/
2. Install app $ adb install $OUT/system/app/SystemUpdaterSample/SystemUpdaterSample.apk
3. Install tests $ adb install $OUT/testcases/SystemUpdaterSampleTests/SystemUpdaterSampleTests.apk
4. Run tests $ adb shell am instrument -w com.example.android.systemupdatersample.tests/android.support.test.runner.AndroidJUnitRunner
5. Run a test file

   $ adb shell am instrument \
     -w com.example.android.systemupdatersample.tests/android.support.test.runner.AndroidJUnitRunner \
     -c com.example.android.systemupdatersample.util.PayloadSpecsTest
   

Accessing android.os.UpdateEngine API

android.os.UpdateEngine`` APIs are marked as @SystemApi`, meaning only system apps can access them.

Getting read/write access to /data/ota_package/

Following must be included in AndroidManifest.xml:

    <uses-permission android:name="android.permission.ACCESS_CACHE_FILESYSTEM" />

Note: access to cache filesystem is granted only to system apps.

Setting SELinux mode to permissive (0)

local$ adb root
local$ adb shell
android# setenforce 0
android# getenforce

License

SystemUpdaterSample app is released under Apache License 2.0.