This should work:
(signs but doesn’t flash with the signed file being left in place in the “Linux_for_Tegra/” subdirectories…which implies even dd could then write the partition if the partition size is large enough for the new tree)
https://github.com/kmartin36/nv-tegra-sign/ does not work is there a write up for it?
This is a third party script, so there is no documentation (other than being in a readable scripted language). The original post introducing this script is here, and might be a good place to ask:
(or you could go to that post and send a private message)
Depending on the error or other log someone here might also be able to help.