flash ubuntu 16.04 into Jetson Tx2

hi, I have problem here
i had flashed my jetson tx2 from sdkmanager(as i need to install cuda).
however it flash had flashed my tx2 into ubuntu 18.04
where it was originally 16.04

the question is,
how do i use the sdk manager to flash my tx2 to ubuntu 16.04 and have all other stuff like cuda installed.
i cant find anything that allow me to swtich the OS version

Hi oneberrybatam2,

Since you used SDK manager to install OS into Jetson TX2, it had automatically updated it to the latest L4T32.2, which comes with Ubuntu 18.04. You can install and use the latest version of CUDA along with other Nvidia provided packages in this Ubuntu version also.
To do this please follow the steps listed in this link: https://docs.nvidia.com/sdk-manager/install-with-sdkm-jetson/index.html

But if you need to downgrade your OS back to Ubuntu 16.04 (which is L4T28.2.1), you need to install and update the OS via Jetpack installer. The steps for the same are provided in this link: https://docs.nvidia.com/jetson/archives/jetpack-archived/jetpack-321/index.html#jetpack/3.2.1/install.htm%3FTocPath%3D_____3

Please note that the older L4T version comes with older versions of CUDA and other packages.