Updating android os
On some devices it will actually download, but you would need a tool like Flash Fire to successfully flash it.
On other devices, it will not actually download, so you’d have to get the OTA file some other way (they are often posted on sites like XDA Developers), and then maybe you can flash it with a tool like Flash Fire.
On newer devices with systemless root, it overwrites the boot image.
Since there’s no way to root Marshmallow without an unlocked bootloader, you’ll completely lose root access if your device’s bootloader is locked. If you’ve unlocked the bootloader, however, Flash Fire should be able to preserve (or at least reinstate) root access once the update is finished.
So: while Flash Fire isn’t guaranteed to work on every device, if you’ve gone the “official” route to root your phone, it will probably work.
It effectively eliminates the need to use recovery to manually backup or restore, and automatically handles un-rooting and re-rooting when flashing update files.
RELATED: Theoretically, it should work on many, if not most, Android 4.2 handsets. On many devices, having root will prevent OTAs from downloading and flashing.