You would download the version of JetPack/SDK Manager (to the PC) which was used for initial flash of L4T/Ubuntu to the Jetson. If you want to see what that L4T release is, then in earlier releases “
head -n 1 /etc/nv_tegra_release” would tell you; if this is a newer L4T/Ubuntu release, then “
dpkg-l | grep nvidia-l4t-core” will tell you.
To see which JetPack/SDK Manager release goes with that L4T/Ubuntu release look at this URL (you will have to go there, log in, and then click the link again to see content):
The instructions are there, but basically you install a Debian package via "
dpkg -i <packagename>. For example, if the file is “
sudo dpkg -i sdkmanager_0.9.12-4180_amd64.deb
From there the instructions tell you how to actually launch and use SDK Manager. You would probably uncheck flash steps and uncheck adding things you are not interested in, e.g., to install NSight would not require any packages being installed to the Xavier (and no flash of Xavier), so this would all be unchecked. This would run on the Ubuntu 18.04 host PC for debugging the running Xavier.