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

System apps (apps with shared user ID set to android.uid.system) cannot install system updates on Android 5 and newer - it's forbidden by a SELinux policy. To be specific writing to /cache is forbidden for system apps. In other words:

• /cache is owned by system user so your app running under system UID can write to it. But only if SELinux is disabled/permissive.
• If you have android.permission.ACCESS_CACHE_FILESYSTEM platform signature permission, you can write to /cache.

You'll need to remove the shared user ID. You still have to sign the app with platform signature and ensure you have the following permissions:

• android.permission.REBOOT
• android.permission.ACCESS_CACHE_FILESYSTEM - to write to /cache
• android.permission.RECOVERY - required on API 21 to reboot to recovery

This will work on Kitkat and Lollipop+ alike.

Answer 2

Before when my app was installed in /system/app I was getting below error:

07-20 10:52:46.512      933-951/? W/RecoverySystem﹕ !!! REBOOTING TO INSTALL /storage/emulated/legacy/Download/Update.zip !!!
07-20 10:52:46.512      933-951/? W/System.err﹕ java.io.FileNotFoundException: /cache/recovery/command: open failed: EACCES (Permission denied)
07-20 10:52:46.512      933-951/? W/System.err﹕ at libcore.io.IoBridge.open(IoBridge.java:409)
07-20 10:52:46.512      933-951/? W/System.err﹕ at java.io.FileOutputStream.<init>(FileOutputStream.java:88)
07-20 10:52:46.512      933-951/? W/System.err﹕ at java.io.FileOutputStream.<init>(FileOutputStream.java:73)
07-20 10:52:46.512      933-951/? W/System.err﹕ at java.io.FileWriter.<init>(FileWriter.java:42)
07-20 10:52:46.512      933-951/? W/System.err﹕ at android.os.RecoverySystem.bootCommand(RecoverySystem.java:389)
07-20 10:52:46.522      933-951/? W/System.err﹕ at android.os.RecoverySystem.installPackage(RecoverySystem.java:337)

I had tried all permissions that were required but I couldn't proceed.

So then since I was using API above 4.2 I tried to put my app into /system/priv-app and it worked for me.

Answer 3

I have problem the same with you when create custom OtaUpdate app in android 5.0.2 and i have resolved it. I will share with you with 2 steps below:

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

For android 4.1.2 :

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

Answer 4

I met the same problem in android 8.
If you add android:sharedUserId="android.uid.system" in AndroidManifest.xml, it should work.

Answer 5

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