[Google Pixel 2 XL Guides, News, & Discussion] Az Biker:
Upgrade to 8.1, TWRP, Magisk, and Cust Kernel (easy steps)

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After running through a bunch of threads, this is how I just upgraded to 8.1 with no issues,and all the steps and links in one post :D Everything works.

My Previous Setup:

Bootloader (unlocked and critical_unlocked) (SEE OP FOR UNLOCKING BOOTLOADER INSTRUCTIONS)

Nov 8.0 Google factory image

Magisk 14.6

TWRP 3.2.1.0

prep work:

-in developer option make sure OEM unlocking is ON

-in developer options make sure USB Debugging is ON

-have the latest SDK toolkit (download in OP)

-have a 2.0 USB in case your 3.0 USB doesn't work properly

-Reboot PC, change between 2.0 and 3.0 cables, and change USB ports if having trouble using fastboot

-make sure all the files you are going to fastboot are located IN the (platform tools folder that contains the fastboot application)

* * * until TWRP fixes the security issue, REMOVE ALL SECURITY BEFORE USING TWRP, reactivate security after rebooting * * *​

*download Latest Google Taimen factory image

follow Updating to a new release (factory image): in OP

(DON'T perform flash-all yet, do that later)

* put TWRP 3.2.1-2 IMG file IN the (platform tools folder that contains the fastboot application), for flashing in fastboot

* put TWRP 3.2.1-2 ZIP in sdcard, for istalling in TWRP

* put Flash's Cust 8.1.0 kernel 8.1 ZIP in sdcard for installing in TWRP

*OPTIONAL*

* put (Magisk latest version) in sdcard for installing in TWRP... Magisk Manager is built into latest Magisk version

***If you're planning on wiping your entire device (leaving the -w intact), put all the "sdcard files" on your PC, after first boot with fresh, factory image, use your favorite root explorer app and add a folder within the sdcard folder (I name mine TO BE FLASHED) and move all the 'sdcard files' files from your PC to here for flashing in TWRP ***

Verify you're connected to PC and Fastboot:

Open a COMMAND PROMPT (type CMD in the address bar) from the same platform tools folder on your PC where the fastboot application is located, and unzipped factory image files (including flash-all.bat) are located, do the following:

type- fastboot devices (should see a serial number, this means you're good)

type- flash-all (this flashes Latest Google Taimen factory image), let it do its thing... (removing the -w [see "updating a new release" in PREP above] stops this from wiping your phone, be sure to SAVE the file after removing the -w... leaving the -w in flash-all.bat, wipes entire device)

-IF TWRP is NOT already installed:

Boot into TWRP using fastboot

(use TWRP IMG file placed in platform tools folder)

fastboot boot <twrp filename.img >

Permanently install TWRP OR to update latest TWRP .ZIP:

(

Or SKIP this step if you do NOT want TWRP perm installed

)

flash TWRP zip

(from within TWRP choose INSTALL and find the TWRP.ZIP file placed on your sdcard)

reboot to TWRP

(deselect install TWRP app, reboot back into TWRP)

flash Flash kernel via TWRP

(placed in sdcard, INSTALL in TWRP, be sure to use the ZIP version, if you use the IMG version you have to reinstall TWRP zip AFTER installing the kernel)

flash Magisk zip via TWRP

(placed in sdcard, and it will automatically install Magisk Manager)

NOTE: Once Magisk is installed, install new versions by clicking INSTALL within Magisk Manager, use "DIRECT" method (for latest version switch channel in manager to BETA)

reboot system

profit!

After reboot:

If you get stuck at "G" screen at boot up, long press power button / hard reboot, should boot normal.

When you see this message on boot up "The bootloader is unlocked and software integrity cannot be guaranteed..........." it is normal an has no effect on your device.

SafetyNet PASSES