When rooting android device, what is changed in device?

Question

Not a Duplicate Claim

If you are tempted to flag this as a duplicate of questions like "How to root my android phone?" or "What can I do with a rooted android device?", then please take the time to read my question carefully. My question is not about those topics.

Question

Out of couriosity, what is changed inside of an android device when it gets rooted? Is it saved somewhere, like in a config file with rooted=true or something like that?

I've extensively tried to google for this, but the information I'm looking for seems to be hidden behind all the results for how to root which phone and what fancy things you can do with a rooted phone, so I couldn't find it. Not even a clue.

Answer 1

Although this article is somewhat old (2011), it goes over the concept of rooting and how rooting is done. Rooting is basically exploiting a security flaw (in phones which do not have have it exposed to public unlike the Nexus line of devices) to get the phone to execute code not from the manufacturer.

http://seasonofcode.com/posts/how-rooting-works-a-technical-explanation-of-the-android-rooting-process.html

Answer 2

Why we need root and how:

Android is designed to not allow arbitrary code to be run as root because root can access any data on the device and monitor the user's interaction with the device, allowing the app to do anything. However Android has security flaws, so apps can exploit those flaws and get root access. Some devices allow users to 'unlock' it, but it will erase all the data on the device first, protecting the data. Other apps use this command to get root privilege and do anything they want: installing apps, interacting with the hardware, read the data on the device, etc.

Technically (from a root app's view):

Rooting adds a command named 'su' to /system/bin or /system/xbin that, when executed, provides a root shell (a shell starting with #).