Before the official release of Google’s latest android 7.0 Nougat in the market. Google is releasing OTA update of the latest android to the Nexus Smartphones. This is first time that Google is rolling out the latest update for the old users without launching the newly OS based smartphone in the market and, by this Google is definitely breaking its tradition.
Devices that receive the ltest Android 7.0 Nougat update are Nexuss 6P, Nexus 9, Nexus Player, Pixel C tablet, and Android One General Mobile 4G devices. It’s a gradual global rollout, possible that not all users get the update notification today but will get the notification in some days. Those users have compatible device can also manually check for the update in settings menu. However users on the Android 7.0 Nougat Developer Preview builds should receive the update first, with those running Marshmallow next in line.
It is very highly unlikely that users will loose data on update the smartphone but still I suggest you to take a backup of the device befor proceding for the update process.