[Nexus 6P General] denk:
Intro

This is a guide for people who want to make some modifications to config files, or other files, on System partition but do not want to root their phone or install custom recovery in order to keep OTAs and some apps, which don't play nicely with rooted phones, working. Examples of those config mods could be changing DPI or changing volume levels etc, which you would only do once and forget about it.

While root allows you to do those kinds of changes from within android, this methods would require a PC.

If you are familiar with temporary booting into a custom recovery, skip to step 5.

The usual i am not responsible for any of your actions / bricked phones disclaimer applies.

Prerequisites

- A working adb / fastboot environment. Please use Android SDK, if you installed your adb and fastboot using other tools, things might not work, so please just install SDK, install Google USB Driver from SDK manager, install Platform-Tools from SDK manager (should be installed by default) and then add your sdk platform-tools path to your PATH environment variable to have it available in cmd in every path.

- Unlocked bootloader

- TWRP image for you phone (.img) https://twrp.me/devices/huaweinexus6p.html

Follow the [GUIDE] Unlock/Root/Flash for Nexus 6P for that.

Instructions

Here is an example of modifying DPI. I prefer build.prop method of modifying DPI because using the adb wm density command usually caused some issues for me, but modifying via build.prop didn't.

1 - With you phone ON, connect it to the PC and make sure adb is working by running

adb devices

and making sure that device is listed

2 - Reboot into bootloader. and make sure fastboot is good to go too. Run commands one at a time:

adb reboot bootloader
fastboot devices

3 - Place your TWRP image file in some easily accessible folder, for the sake of this example i will use C:\Mods.

4 - Temporary boot into TWRP (we are not flashing it here at all).

fastboot boot c:\Mods\twrp-2.8.7.0-angler.img

Here is where things may not work. If you don't see your phone boot into TWRP then either your adb / fastboot environment not setup correctly (installed via a tool instead of SDK) or your img file is corrupt.

One thing that works for me when TWRP refuses to boot is to restart cmd and issue the command again this closes and reopens adb/fastboot daemon.

5 - Once TWRP is up on your phone it may display a warning saying "TWRP has detected an unmounted system partition". Swipe to allow modifications at the bottom. This screen may not come up at all.

6 - Go to Mount >>> Tick System >>> Make sure "Only Mount System Read Only" is

unticked

>>> Press Back button

7 - Back on your PC check if your device is listed

adb devices

8 - Pull the file you need to modify from system partition to your PC. Please note the direction of the slashes:

adb pull /system/build.prop c:/Mods

9 - Now you should see build.prop in your c:\Mods folder. Use Notepad++ or something like that to edit the file. Find the line with lcd_density= and change it's value to whatever you need and save the file.

10 - Push the file back to your phone:

adb push c:/Mods/build.prop /system

11 - Reboot

adb reboot

12 - Profit.

Hope this will help anyone who is looking to do some mods without installing custom recovery and rooting your phone.

Cheers.