Google starts rolling out Android 6.0.1 update to the nexus series smartphones and tablets, the update was initially rolled out to Android One smartphones last month. The new update will still be called as Marshmallow as it is a minor OS update. The newly rolled out update brings new Emojis and December’s security patch, also brought back the ‘until next alarm’ option for do not disturb mode and for the old nexus smartphones the update adds double-tap power camera launch shortcut.
— Nexus (@googlenexus) December 7, 2015
Google has also released the factory images of the Android 6.0.1 update for Nexus 5, Nexus 5X, Nexus 6, Nexus 6P, Nexus 7 (2013), Nexus 9 and Nexus Player (build Nexus MMB29M) so that you can flash it directly without waiting for the official OTA update. The flashing instructions and steps are being mentioned in the google developers page.