[Shield Tablet Q&A, Help & Troubleshooting] telleri:
From step 8 on is the simple root procedure if you have drivers and ADB setup already.

Pre-Requisites:

•Minimal ADB/Fastboot (official page)

•Shield Family Drivers (original page)

•TWRP Recovery (experimental)

•SuperSU 2.65 BETA for flashing with TWRP (newer version maybe here)

Note: Unlocking the bootloader will ERASE EVERYTHING internally (not on your external SD card if present). Make sure you have everything saved off and backed up. You’ll have to resign into Google – so if you use two-step authentication, be sure to have your Google Authenticator app ready.

Preparation

1.Install Minimal ADB and Fastboot if you do not already have it installed.

2.Ensure the Shield Family drivers are extracted somewhere on your system and you know where they are.

3.Make sure you know how to get to Device Manager on your PC.

4.Extract TWRP Recovery image (and do yourself a favor and rename it to something easy like twrprecovery.img). Put this in your Minimal ADB and Fastboot folder (usually c:program files(x86)Minimal ADB and Fastboot).

5.Copy supersubeta.zip into your Minimal ADB and Fastboot folder

6.Plug your Shield Tablet K1 into the PC with USB cable.

7.Confirm drivers for ADB are installed: 1.On your PC, go to Device Manager. Find the yellow (!) ADB device. If none exist, you probably already have drivers. Skip to step 8.

2.Right click the device and select Update Driver.

3.When offered, browse your computer for the driver and point it to the Shield Family Drivers folder you extracted in Preparation Step 2 above.

4.When finished with the driver install, the (!) yellow device should be gone.

8.Enable Developer mode on Shield Tablet K1 1.On the Shield Tablet K1, go to Settings->About->Build (tap 7 times on the BUILD to unlock developer mode)

9.Enable USB Debugging on Shield Tablet K1 1.Settings -> Developer -> Debugging; set to On

2.A popup should appear asking for this PC’s authorization. Check the Don’t ask again for this PC box and select Allow. If it doesn’t show up now, it will later.

Root Procedure

1.Reboot into Bootloader on Shield Tablet 1.Launch Minimal ADB and Fastboot from the Start Menu or icon. This puts you in a black DOS box.

2.Type “adb devices” and make sure your Shield Tablet K1 appears. Note: If you didn’t have a popup on your Shield Tablet K1 screen in Step 9.2 above, it probably will appear now. You’ll have to authorize the PC before it will show up under adb devices.

3.Once you see your Shield Tablet K1 when you run “adb devices” you’re ready to proceed.

4.Type “adb reboot bootloader” and hit enter. The Shield Tablet K1 should reboot into the bootloader screen.

2.Verify Fastboot Drivers are installed: 1.On your PC, go to Device Manager.

2.See if a yellow (!) exists that mentions FASTBOOT. If not, continue to Step 3 to unlock bootloader.

3.Right click the device and select Update Driver.

4.When offered, browse your computer for the driver and point it to the Shield Family Drivers folder you extracted in Preparation Step 2 above.

5.When finished with the driver install, the (!) yellow device should be gone.

6.Type “fastboot devices” and make sure your Shield TV is visible.

3.Unlock Bootloader (skip if you already unlocked your bootloader) 1.Type in “fastboot oem unlock” and hit enter. EVERYTHING ON THE TABLET WILL BE LOST!

2.You will see a prompt on the Shield Tablet K1.

3.Confirm to unlock the bootloader. Do not be impatient! Let it finish.

4.Reboot to Shield Tablet K1 Interface 1.Once the bootloader is unlocked, reboot the Shield Tablet K1 and return to the Shield tablet K1 main interface.

5.Repeat Preparation Steps 8 and 9 above to re-enable Developer/USB Debugging. Note: at some point you will have to re-authorize your PC again; if an ADB command fails, be sure to look at your Shield Tablet K1 screen for the authorization prompt.

6.Push supersubeta.zip to the Shield Tablet K1 1.In the Minimal ADB and Fastboot DOS window, type (or cut and paste for more accuracy): “adb push supersubeta.zip /sdcard/”

2.You should see text indicating the file was copied over correctly.

7.Reboot to Bootloader 1.Type “adb reboot bootloader” and hit enter. The Shield Tablet K1 should reboot into the bootloader screen.

8.Fastboot with TWRP 1.Type “fastboot devices” and make sure your Shield Tablet K1 is visible.

2.If your Shield Tablet is listed, type “fastboot flash recovery twrp-20151227-EXPERIMENTAL-shieldtablet-m.img” (or whatever you named it) and hit enter. If your TRWP image filename has a space in it, you may have issues.

3.On the Shield Tablet K1, use the volume rocker to select RECOVERY MODE and tap the power button to select. Note: There are reports that you should do a full reboot between flashing TWRP and flashing SuperSU. IF you find that TWRP doesn’t survive using this method: 1.Instead of selecting Recovery Mode, in Minimal ADB window, type: “fastboot reboot”

2.Once rebooted to Android, use Minimal ADB window, type: “adb reboot bootloader”

3.When the tablet is in bootloader, type: “fastboot boot recovery”

4.After 15 seconds or so, you should see the TWRP Recovery screen. Note: This experimental version has some UI issues, just keep at it.

5.You may be prompted with something to do with the system being READ ONLY. Accept the default and swipe.

9.Install SuperSU 1.Select INSTALL.

2.Navigate and select supersubeta.zip.

3.Follow the instructions to Swipe to Flash

4.SuperSU will install.

10.Reboot to System 1.Select REBOOT then SYSTEM from the TWRP menu

2.Answer NO if asked anything about fixing or restoring ROOT

11.Run SuperSU application and apply any updates 1.Once you are back up and running (first boot can take a little longer) find the SuperSU app installed on the Shield Tablet. Run it and perform any upgrades (select “Use Normal” if asked).

12.You are now rooted! Test your root apps now.