Finally, Google has released the stable version of Android 7.0 Nougat, the next big Android OS update, with many new features. Nexus and Android One devices running on Android Beta program will get the incremental OTA (over the air) update soon and for devices running on Marshmallow may need to wait little long time. However, as the OTA update is rolling out in phases, it will take one or two weeks to get the update on all devices.
Android 7.0 Nougat OTA images for supported devices is now available for download, which means tech-savvy users can flash the firmware right away, without waiting for the OTA (over-the-air) update. Currently the update (NRD90M) is available for Nexus 6P, Nexus 5X, Nexus 9 (Wi-Fi) and Pixel C (courtesy to AP). Other supported devices Nexus 6, Nexus 9 (LTE), General Mobile 4G (Android One) and Nexus Player will get the update soon.
Here is a quick guide to flash Android 7.0 Nougat manually on Nexus 5X, Nexus 6P, and Nexus 9. Note that the mentioned OTA images are not incremental update; they are full firmware, which you can sideload on your device via ADB (Android Debug Bridge) command.
Also, note that the below method does not need to unlock your bootloader, and your data should remain intact. However, Google recommend you to backup any important data you have on your device.
2. Rename the downloaded zip file to ‘update.zip’ and then move the file in the ADB installation directory (usually it will be at C -> Users ->User – ADB).
3. Power off the Nexus and boot it into Recovery mode (Press and hold Power and Volume down buttons together, then select ‘Recovery mode’ and confirm it by Power button. When an exclamation mark appears, press Power button and then press Volume down button)
4. In recovery, select ‘Apply update from ADB’.
5. Connect your Nexus 6P/Nexus 5X to PC via USB Cable.
6. Go to the ADB folder (where you have placed the update zip file) and launch a command prompt window there (Press Shift key, right click and choose ‘open command prompt window here’)
7. In the command prompt, issue the below command:
[It should list your device in the command prompt. If not, it means fastboot drivers not installed on your computer. Install and proceed)
8. If your device is listed, continue the next step. Type the below command in the command prompt and press enter key:
adb sideload update.zip
9. Wait for all the files to be installed. Once done, reboot the phone by selecting ‘Reboot system now’ in your phone.
Note that the first boot process will take almost 30 minutes (depending on installed apps). For any extra help, leave them in the comment section below (Source – AP)