- Download and install USB drivers for the Nexus 6P on your computer.
- Enable USB debugging option by pressing Menu > Settings > Applications. Navigate and tap on Developer Options to ensure that USB Debugging is enabled.
- Your Nexus 6P should be rooted.
- Make sure that TWRP recovery is installed.
- Ensure that your Nexus 6P carries more than 70% charge.
How to update Nexus 6P to Android 7.1.1
Download LineageOS 14.1 Android 7.1.1 custom firmware on your computer. Also, download the GApps package from here.
- Connect your Nexus 6P to your PC using the USB cable and copy the downloaded files to the SD card of your device.
- Disconnect your Nexus 6P and power it off.
- Now boot it into the recovery mode: press and hold Volume Up, Down and the Power buttons simultaneously. Use Volume keys to highlight and Power button to select.
- Data wipe operations: go to wipe data/factory reset and confirm the operation. Also, wipe cache partition and finally go for wipe dalvik cache to clean it up too.
- Now, select install zip from sdcard and then choose zip from sdcard. Locate the LineageOS 14.1 Android 7.1.1 Nougat zip file and confirm its installation.
- When the ROM installation completes successfully, repeat the above step for installing the GApps package.
- Once done, go back to main recovery menu and select reboot system now.