What is the Difference between a Device Policy Controller (DCP) app and a System App?

Question

Is there any difference in the privileges of an Android DPC application and a system application? Will a system application be able to perform all the functions that a DPC can perform such as setting the device to Single Use Mode?

Answer 1

Well, there is no-such difference in privileges as far as the Android system is concerned.

If you look at the Android Platform Architecture , you will find that the even a normal user app have the same access to all the system resources as a system app.

Apps included with the platform have no special status among the apps the user chooses to install. So a third-party app can become the user's default web browser, SMS messenger, or even the default keyboard (some exceptions apply, such as the system's Settings app).

You can read about more differences in system and user app here .

Also, another interesting point to note is that on a production device there are only 3-processes that run as root , the Zygote , the app_process and the adbd (though it doesn't allow root access directly using adb ). That means, all other apps run under their own user_id with different permissions and since Android doesn't differentiate between apps, two apps having same permissions are allowed same privileges and access to resources, regardless of the fact whether it is a system app or a user app.

Now, to answer your question, if a system app has the same privileges as the DPC app, then yes the app would be able to perform the given task (like setting the device to Single Use Mode) same as the DPC without any problem.

As a side note, if you are planning to create a DPC for you organisation, using the DPC SUpport Library is better than creating and shipping a system app.

PS To change a System setting your app would need the WRITE_SETTINGS permission.