L4T for Jetson Xavier flashed with Jetpack 4.2

What is L4T? Do I need to install it separately if I flash my Xavier with jetpack 4.2? If yes, please guide me to the download url.

Thanks

The operating system installed is Ubuntu. This comes with purely open source content. Then NVIDIA drivers are added on top of the Ubuntu for direct/accelerated hardware access, it becomes known as “Linux 4 Tegra”, or “L4T”. When you flash you use a tool from a Linux/Ubuntu desktop PC…the installer has been known as “JetPack” (or more recently “SDK Manager”).

The installer actually installs only to the PC, but acts as a tool and installs L4T or extra packages (mainly CUDA-related items) on both PC and Jetson. It is possible to flash on command line, but few people do. When you run JetPack (or SDKM), then the tool does all of the downloading for you. Sometimes people don’t realize that JetPack allows you to set only to flash L4T onto the Jetson or only to install packages, although the default is both.

If you were to flash on command line, then you’d download the driver package and sample rootfs. You’d unpack the rootfs in the right place, run the command to overlay the NVIDIA-specific drivers onto that, and then flash with the Jetson in recovery mode. JetPack/SDKM can do all of this for you, but mandates using an Ubuntu host. You can use the driver package plus sample rootfs on command line with any 64-bit Linux o/s.

JetPack/SDKM 4.2 corresponds to L4T version R32.1. That particular release adds Ubuntu 18.04 to the Jetson, and the CUDA-related options for that release. JetPack3.3 installs L4T R28.2.1, which is ubuntu 16.04 plus NVIDIA drivers.

NVIDIA SDK Manager URLs and Information:
Installer: https://developer.nvidia.com/embedded/dlc/nv-sdk-manager
Instructions 1 (Download/Run): http://docs.nvidia.com/sdk-manager/download-run-sdkm/index.html
Instructions 2 (Install Software to Jetson): http://docs.nvidia.com/sdk-manager/install-with-sdkm-jetson/index.html