Originally Posted by soy.lor.n
OK new new question:
If we want to switch back to stock after flashing a different ROM, but want to stay rooted, do we just do this part?:
adb reboot bootloader
fastboot -w update image-mysid-icl53f.zip
Will this just flash the stock factory image and take us back to normal, maintaining root and bootloader unlock? (assuming your radios are already updated...)
It's not too hard to unroot and then reroot, but I'd rather have a better understanding of what each step actually does
Well, flashing with the above command will replace all of your OS (even the root parts), so you lose root at that point...but yes, the bootloader and radios are untouched by the above component being flashed (that's the OS part (boot/recovery/system images)).
Your bootloader will remain unlocked (its only affected by the fastboot oem lock
and fastboot oem unlock
You should be able to just use the above command to return to stock as long as the radios and the bootloaders haven't changed. That being said, whenever Google publishes a new OTA and the accompanying stock image package, you'll want to keep everything (radios, bootloader, OS (boot/recovery/system images)) in-sync.