[Google Pixel 2 XL Guides, News, & Discussion] Schroeder09:
About a week ago I updated to Android 8.1. I'm a total noob at this. I thought I'd share my process with a lot of little, implied steps in it that a lot of you pros skip over when explaining things to us dummies. spencer92a walked me through all this. Thanks a million to him.

To take the 8.1 update, get the flash kernel, and maintain root here is what I did:

****Prior to actually beginning the process I disabled my substratum themes, removed all security (PIN and fingerprints from my phone), and uninstalled magisk. Make sure you have the latest platform tools from Google. I used v27 when I flashed this a week agom. The platform tools folder is referred to as "platform tools folder," "ADB folder," and "fastboot folder" in the write-up below. NOT doing some of these things has caused people issues and bootloops, so please complete these pre-requisites.***

1. Go to Google and download the 8.1 factory image to your PC. (https://dl.google.com/dl/android/aosp/taimen-opm1.171019.011-factory-2df1c1cb.zip))

2. Download twrp 3.1.1 beta 2 image to your PC. ***You need the .img file***

3. Download twrp 3.1.1 beta 2.zip to your PC.

4. unzip the factory image and copy all files to the fastboot directory (E.g. C:/fastboot). there will be a zip folder in this factory image folder that has the same name as the top level folder. unzip it, copy its files (boot.img, radio.img, etc.) and paste them into your adb fastboot folder too.

5. Download Flash kernel (Now 2.01 I think) and Magisk 14.5 to your PC

6. Connect your Phone to PC. Make sure it is in data transfer mode. A notification should populate in your notification pull down menu that allows you to make this selection.

7. open a cmd in the fastboot folder (hold shift and click right mouse button. Select cmd window or power shell. They're the same thing basically, but your PC may vary from another on what populates here.)

8. write in the cmd "adb reboot-bootloader" (Without the "" of course) and hit enter.

9. Give the phone a minute. It'll reboot. Now it's in bootloader (And ready for fastboot)

***10. Now execute the flash-all.bat, but WAIT- You can here remove the "-w" from the file before flashing so you dont wipe your phone. Right click on the flash-all.bat file, rename it to "flash-all.txt" so you can open it in notepad, click Ctrl+f to open a find window, search "-w", delete only those two characters, close the file, rename it to "flash-all.bat" THIS IS AN IMPORTANT STEP IF YOU DONT WANT TO LOSE DATA*** What this step is doing is flashing all the factory files in the ADB folder that you copied over to it in step 4.

11. Wait until the phone is rebooted

12. Reboot to the bootloader (restart the phone. As soon as the phone screen turns black hold the volume down button). After this drag your twrp 3.1.1 beta 2.img to the fastboot folder.

13. back to the cmd. write "fastboot boot twrp311 beta 2.img" you may have named the .img file something else. Another SUGGESTED alternative is to type "fastboot boot xxxxxx". Now after the SPACE behind the word "boot" you won't actually type "xxxx" you'll drag the .img file from folder into cmd window. This is nice because these file names are often long and then you don't have to type directories and stuff.

14. When Twrp shows up (1-2mins), you can push twrp.zip and Magisk.zip and kernel.zip via adb "adb push xxx /sdcard/Folderofyourjoice". I used "/sdcard/downloads" because it's easy. There needs to be a SPACE behind the "xxx" and again, the xxx is where I recommend you drag the file names. When you have pushed the files look for them in twrp on the install tab. If you inststalled them in the downloads folder they should be right there. I think twrp's default folder that it looks at is downloads.

If you have trouble with adb push you can press the reboot button in twrp and choose system. Then you can drag the .zip files to your downloads folder on your PC. This will require you to do step 13 again because when you fastboot the twrp.img it is only temporary. If you do this, skip step 14 and go to 15.

15. Now you can flash twrp.zip, flash kernel 2.0.zip, and then Magisk. Hit the install tab in twrp and do each zip file. After each file you will be presented with the option to reboot or flash more files (or something like that). Flash all your files and only reboot into your system after the last file.

16. reboot

17. Done. Go into your settings, system, and about phone to see which kernel and/or version of Android you're on.

I hope this helps other rookies like myself. Again, thanks to spencer92a for helping me through all this. Multiple PMs were exchanged. I appreciate the investment if your time, and I'm sure someone out there will see this. They'll appreciate it too.