Here you can find the necessary download links to GNU/Linux OS to use with your Arduino Yún Rev2 board.
Download the latest stable GNU/Linux OS for your Yún. It makes your Yún more stable and feature rich.
Follow the steps in the Yún Sys Upgrade tutorial.
This procedure is only recommended to advanced users who wish to completely re-flash the Yún including its U-Boot bootloader. These instructions on reflashing the base images are for reference only. Following them will void your Yún's warranty.