[Google Pixel 2 Guides, News, & Discussion] Diesel_Jeremiah:
UPDATE:

In the thread @Pianobeats and @Telperion have successfully updated with less steps.

They flashed the newest Jan update flash-all without removing Magisk, Kernel, or TWRP. This eliminates the need to flash the current security update you are on and reduces the number of steps dramatically.

Clarification:

In the factory image zip you'll drill down through the files until you find flash-all.

Open that in a text editor

.

Near the end you'll find "-w"

Delete it and save the flash-all.

This will make it so the update

does not

wipe your device.

_______________________​

I felt adventurous and decided to try updating.

I updated to latest adb & fastboot from here: SDK Platform Tools Release Notes

At first I tried using the Magisk Uninstaller Zip;

it did not work.

In bootloader, I used the DEC 2017 flash-all (-w removed). This worked to get me out of the bootloader and Magisk was uninstalled.

I recommend just uninstalling Magisk from the app.

EDIT:

On my second Pixel 2 ( I have two), uninstalling Magisk from the app did not work.

It stuck me into the same error in the bootloader as my first phone.

Flash-all (-w removed) worked to return me to the system.

No need to flash stock boot or dtbo.

In cmd window:

adb devices

Verify serial number (working adb & fastboot)

adb reboot bootloader

Cycle through to recovery.

Once in recovery hold PWR and press volume up once

Volume down to highlight "Apply update from ADB"

adb sideload <walleye-ota-opm1.171019.013.zip>

NOTE: Go to the where you saved the OTA zip "walleye-ota-opm1.171019.013". On the top menu you should see "copy path" or alternatively you can right click > properties > Location. Copy that string (IE "C:\Users\you\desktop\...")

Type: adb sideload and *Ctrl +v* to paste (Much easier)​

I rebooted to bootloader; I verified the change from boot slot b to boot slot a.

After boot > Notification: Android System - "Finishing Android Update..."

System is sluggish. Probable background processes.

adb reboot

Significantly longer reboot at Google Icon with Progress bar than normal (about 4 full minutes)

adb reboot bootloader

fastboot boot "twrp-3.2.1-0-walleye.img"

NOTE: Go to the where you saved the OTA zip "twrp-3.2.1-0-walleye.img". On the top menu you should see "copy path" or alternatively you can right click > properties > Location. Copy that string (IE "C:\Users\you\desktop\...")

Type: fastboot boot and *Ctrl +v* to paste (Much easier)​

TWRP > Install > twrp-pixel2-installer-walleye-3.2.1-0.ZIP

Wipe cache > Reboot system

adb reboot recovery

TWRP > Install > Snoke R1

Wipe cache > Reboot system

adb reboot recovery

TWRP > Install > Magisk V15.2

Wipe cache > Reboot system

After reboot > "Android is starting" for a half second

NOTES:​

Magisk = V15.2

ctsProfile: true

basicIntegrity: true

(Screen shot attached)

Viper4Android 2.5.0.4 = Installed and Processing properly (Screen shot attached)

Magisk Notification > DTBO Patched, please reboot > "Android System internal problem pop up"

(No, this does not affect anything.)

Also, this proves that even after mounting /system via TWRP OTAs are still usable.

NOTES #2:​

I have two Pixel 2 phones.

One for work and one for personal.

I performed the above on my personal, though havrt not had the time to update my work phone.

An OTA pushed to your device will not work on phones that have TWRP, Magisk, custom Kernel.

Screen shots attached.