my galaxy nexus is asking for update.. how can i keep my root

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http://forum.xda-developers.com – i'm running 4.1. and since a few days ago, my nexus is saying the update is ready and i should update.. i guess it's 4.2? anyway, last time i updated like this, i lost my root.. so what's the easiest way to accept this system update but still keep my root? (HowTos)