SU 权限被拒绝，尽管 Android 模拟器上有 ABD Root

Question

I wanted to write commands to SU like this:

Java.Lang.Process process = Java.Lang.Runtime.GetRuntime().Exec("su");

I get the following error unfortunately:

'Cannot run program "su": error=13, Permission denied'

I have ran adb root and I have access to shell right now but this error keeps popping up. I'm using Xamarin.Android and Visual Studio.

Answer 1

Using adb root is not the same as having a rooted device where you can access the su command. There is a reason as to why the command is only available using Android Debug Bridge (adb) on emulators.

You can use su on devices that are rooted. I wrote a blog post about how to do this with Xamarin here: https://blog.ostebaronen.dk/2018/07/xamarin-and-java-processes.html

Instead of using Java.Lang.Runtime.GetRuntime().Exec() to start the process, you can use ProcessBuilder instead, which allows you to build the command nicely like and await the result like:

var builder = new ProcessBuilder("echo", "hello");
var process = builder.Start();
var exitCode = await process.WaitForAsync();

For starting some process as root you can do:

var builder = new ProcessBuilder("su", "-c", "echo hello");

However, doing this does not change the fact that the Emulator you are using is not rooted as devices would be. So none of this will work as you expect.

If you are looking to root your emulator, like a device would be rooted. You would need to install something like SuperSU or Magisk on your AVD. This is very well described here: https://medium.com/@anthony.f.tannous/android-10-emulation-of-magisk-supersu-on-an-aosp-avd-de93ed080fad

This will involve:

1. Acquiring root using adb root
2. Mounting the /system/ partition
3. Pushing some files which override the su and other binaries with patched ones
4. Starting a SU daemon