These are the instructions to root AT&T Samsung Galaxy S6 smartphones running on Android 5.1.1 Lollipop updates. The guide gives AT&T S6 users a tethered root because the developer still cannot unlock the bootloader or flash a necessary unsigned kernel on the device. There are a few warnings and things you should know before flashing these files on your AT&T S6, so make sure you read the ‘before we begin’ section carefully.

REQUIREMENTS

• The guide is working for the OJ7 and OJ9 build numbers only. It is not confirmed to be working on any other build ID’s.
• The following guide is intended to root the Samsung Galaxy S6 smartphone for AT&T subscribers. The AT&T variant of the Galaxy S6 comes with the SM-G920A model number. You can find out the model of your S6 by tapping on the Menu > Settings > About Device > Model Number.

BEFORE WE BEGIN

• Download and install the Samsung USB Drivers on your computer before you start the guide.
• Make sure you have the Developer Options turned on and the USB Debugging Mode enabled by tapping on the Menu > Settings > Developer Options > USB Debugging Mode.
• The tethered root means that you will need to run a command or have a script ready each time the device turns off.
• There is a separate download link for the OJ9 firmware. You will find the file on the same page as the OJ7 firmware on the XDA Developers thread. 
• Once you root the AT&T Samsung Galaxy S6 smartphone using the guide below, you will always need to boot with the root-boot.cmd if you are running Windows, and the root-Boot.sh if you are running Linux.
• The original poster of this rooting method mentions the drivers don’t always work for people using this method. If you find your Windows drivers not working, remove the driver and scan for hardware changes. Read the notes on the thread given in the link for more details.

HOW TO ROOT AT&T SAMSUNG GALAXY S6 RUNNING ANDROID 5.1 LOLLIPOP

1. Download your rooting files for the OJ7 and OJ 9 firmware build number from here.
2. Download the Odin flash tool for your Windows computer from here.
3. Extract the files to the desktop of the computer by dragging them over to the desktop from the default downloads folder and then choosing the “extract here” from the menu.
4. Right-click the Odin executable and select “run as administrator”.
5. Boot the Samsung Galaxy S6 smartphone to download mode and then connect it to the computer.
6. Click the AP or the PDA button you can see from the Odin user-interface.
7. Browse the desktop for your rooting files.
8. Do not make any adjustments to the default settings you get from the Odin flashing tool’s user-interface.
9. Click on the Start button and wait for the flashing to complete.

Soon you should get a pass message from the Odin user-interface and your Samsung Galaxy S6 from AT&T will reboot. Hit the Google Play Store for the root checker application and open it up on your device to check the root status. You can agree to any demands that root checker app might have waiting for you when you open it, such as granting SuperUser access to your device.