Android development RecoverySystem.installPackage() cannot write to /cache/recovery/command permission denied

Question

I have been asked to write a small simple app for an Android-based product. The device comes with two Android system images with different features. The app I\'m writing is

Answer 1

For Android 5.1.0

1. Add android:sharedUserId="android.uid.system" in AndroidManifest.xml
2. Push your apk to system/priv-app

3. and then

   adb root
   adb shell setenforce 0