How can I download Linux For Tegra R21.5 ?

today I updated jetson TK1 using this command
usdo apt-get update

suddenly TK1 stopped and I shut down it by force.

After that it does’n work properly, So I want to reinstall Ubunto in my TK1

I had tried install Linux for tegra R21.5 here

But I can not find download location and it is my problem.

How can I download Linux For Tegra R21.5 ?

The URL you gave has the R21.5 for download. You could use JetPack, or directly use the driver package plus sample rootfs. JetPack is a front end for the driver package plus sample rootfs, and has other features in addition (such as making available other software to both host and Jetson). You do have to be logged in for some of the software to download.

Some URLs to check:
https://developer.nvidia.com/linux-tegra-r215
https://developer.nvidia.com/embedded/dlc/l4t-Jetson-TK1-Driver-Package-R21-5
https://developer.nvidia.com/embedded/dlc/l4t-Jetson-TK1-Sample-Root-Filesystem-R21-5
https://developer.nvidia.com/embedded/jetpack

Essentially the driver package is for flashing, the sample rootfs is the actual software to be flashed. The driver package does do some adjustments to the generic sample rootfs before flashing.