The Android operating system that you find running on the Samsung Galaxy S6 smartphone is based on Linux. The Linux kernel is naturally a very secure operating system for computers, but the malware threat that is present from a mobile operating system forced Google Android developers to block people from being root users by default. A root user on Android is the equivalent of being an administrator from a Windows operating system. Naturally, we are assigned the administrators account when we first install the Windows operating system on a new computer, and that is the account you need to use if you are installing lots of nice things. The same goes for Android operating system in the sense that you are unable to install much of the goodness out there in the Google Play Store and online without being a root user.
For people to be root users on the Samsung Galaxy S6 smartphone, they need to find an appropriate rooting guide that teaches them how to root the operating system for their particular device. For Samsung devices, that is often based on the model number and software versions.
- The following guide is made for the Samsung Galaxy S6 smartphone that comes with the SM-G920F model number when it is running on the Android 6.0.1 Marshmallow software updates. You can find out the model number of your Samsung Galaxy S6 smartphone and the Android software versions it is running by tapping on the Menu > Settings > About Device.
- You must have a computer that is running a version of the Windows operating system to use the Odin flashing tool associated with this guide. You do not get the flashing application to work from a computer that is running any version of MacOS or Linux distributions.
- You must install a custom recovery on the Samsung Galaxy S6 smartphone  before you can root it using the steps in this guide which installs and enable the SuperSU via the custom recovery image that you installed.
BEFORE WE BEGIN
- Unlock the Developer Options menu on the Samsung Galaxy S6 smartphone by tapping on the Menu > Settings > About Device > Build Number at least seven times and you should see a message make a brief appearance on the screen of the phone that lets you know that you are now using the device as a developer. That, of course, means you have the Developer Options menu unlocked so now we can turn on the USB Debugging Mode.
- Get access to the Developer Options menu and enable the USB Debugging Mode by tapping on the Menu > Settings > Developer Options > Check the box that is currently empty for the USB Debugging Mode. Now you can navigate out of the Developer Options menu on the Samsung Galaxy S6 smartphone, and the Android operating system will remember your preferences.
HOW TO ROOT SAMSUNG GALAXY S6 SM-G920F RUNNING ON XXU3DPDP ANDROID 6.0.1 MARSHMALLOW
- Download the SuperSU application that roots the Samsung Galaxy S6 smartphone from here  and has it on the desktop.
- Connect the Samsung Galaxy S6 smartphone to the computer with the USB cable and then copy the stable version of the SuperSU zip file to the internal storage SD card folder that is on the computer.
- Unplug the Samsung Galaxy S6 smartphone from the computer and the USB cable and press the Power button to turn it off completely.
- Boot the Samsung Galaxy S6 smartphone by holding the hardware button combination for the recovery mode and then the custom recovery boots up on the display.
- Press the ‘Backup’ button from the main recovery menu and take the NANDroid Backup by following the guidelines on the screen.
- Tap on the ‘Install’ option from the main Recovery menu and then browse the SD card for the stable version of the SuperSU that you transferred there earlier from the computer.
- Follow the on-screen instructions to finish installing the SuperSU file and it enables the SUperSU for you, so you are using the device now as a root user.
- Choose the option that reboots the system from the main recovery menu.
In conclusion, that is how to root Samsung Galaxy S6 SM-G920F smartphones running on the Android 6.0.1 Marshmallow software updates when the have the XXU3DPDP firmware build number. The SuperSU version that is running on your Samsung Galaxy S6 smartphone now is the systemless version which is going to unroot each time you apply a factory reset.