If you are the kind of person who does not like to wait for something like an OTA update to roll around to your mobile device in order to get the latest operating system update from Google, you may be glad to know that factory images for several Nexus devices have now been posted. If you own a Nexus 5, a WiFi-only version of the Nexus 7 (2012 or 2013 version), or a Nexus 10, you can download the factory images from the Android Developers site.
If you go this route, you do need to know how to manually install the image on your device. That is not an overly complicated process, but it does require a few tools and the ability to do some research if you run into problems.
Updates to Android Lollipop for the 3G/4G LTE versions of the Nexus 7 as well as the Nexus 4 are not yet available. Hopefully it will not be much longer for those to surface.
source: Android Developers
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