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diff --git a/sample_updater/README.md b/sample_updater/README.md
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--- a/sample_updater/README.md
+++ b/sample_updater/README.md
@@ -1 +1,72 @@
-# System update sample app.
+# SystemUpdaterSample
+
+This app demonstrates how to use Android system updates APIs to install
+[OTA updates](https://source.android.com/devices/tech/ota/). 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.
+
+
+## Running on a device
+
+The commands expected to be run from `$ANDROID_BUILD_TOP`.
+
+1. Compile the app `$ mmma bootable/recovery/sample_updater`.
+2. Install the app to the device using `$ adb install <APK_PATH>`.
+3. Add update config files.
+
+
+## Update Config file
+
+Directory can be found in logs or on UI. Usually json config files are located in
+`/data/user/0/com.example.android.systemupdatersample/files/configs/`. Example file
+is located at `res/raw/sample.json`.
+
+
+## Development
+
+- [x] Create a UI with list of configs, current version,
+      control buttons, progress bar and log viewer
+- [x] Add `PayloadSpec` and `PayloadSpecs` for working with
+      update zip file
+- [x] Add `UpdateConfig` for working with json config files
+- [x] Add applying non-streaming update
+- [ ] Add applying streaming update
+- [ ] Prepare streaming update (partially downloading package)
+- [ ] Add tests for `MainActivity`
+- [ ] Add stop/reset the update
+- [ ] Verify system partition checksum for package
+- [ ] HAL compatibility check
+- [ ] Change partition demo
+- [ ] Add non-A/B updates demo
+
+
+## Running tests
+
+1. Build `$ mmma bootable/recovery/sample_updater/`
+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
+   ```
+
+
+## Getting access to `update_engine` API and read/write access to `/data`
+
+Run adb shell as a root, and set SELinux mode to permissive (0):
+
+```txt
+$ adb root
+$ adb shell
+# setenforce 0
+# getenforce
+```