Android 7.1 Nougat update is available for Nexus 4, but in the form of NitrogenOS. This is a custom OS that will bring features of the Nougat to the latest Nexus devices.
NitrogenOS is not exactly official firmware. It is a custom ROM specifically made for Nexus 4 users that want to run the Android 7.1 Nougat update on their devices. As such, some of the features in the actual original firmware may not work properly in the Nexus.
Important: Precautions must be taken as well before deciding to proceed with the upgrade. This is not because NirogenOS is not an official firmware and the upgrade may cause unexpected results depending on the individual device. Before trying to upgrade, make sure you have done all the necessary precautions, like crucial data backup and battery charging. The Nexus must be charged up to at least 80% before the attempt.
The device needs to be rooted for this work, with the most recent recovery system in place. The bootloader must also be unlocked and USB Debugging is enabled.
Now for the actual steps: the first thing you need to do is to download the NitrogenOS file and save it on your PC. Google Apps must also be downloaded.
Next, you should plug the Nexus to the PC via USB and save the downloaded files on the device’s internal storage. After that, power the device off and unplug it from the PC.
At this point, you need to boot the device into recovery mode. To do this, you must press the Power Button, Volume Up, and Volume Down buttons simultaneously. When you see a Bootloader or Fastboot menu, you can release it.
On the menu that appears, you need to select Bootloader > Recovery. You can use the Volume control buttons to navigate and the Power button to select.
At this point, you should select Backup/Restore to create a backup. After this, go back to the main menu to perform a complete wipe and factory reset, and to wipe cache partition, as well. Wiping the Delvik cache is a must, as well, and it can be done by going into Advanced > Wipe Delvik Cache.
Now comes the main installation step. Find the choice that says Install Zip from sdcard > choose zip from sdcard which can be found in the main menu of the Recovery boot. It will prompt you to select a file; locate the file you downloaded earlier and select it.
Next, redo the previous step but this time, for Google Apps. After all this, you should do a system reboot. Hopefully, if all goes well and as expected, you will get the Android 7.1 Nougat update on your Nexus 4 via NitrogenOS.
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