Changed permissions in usr folder. Can initiate ubuntu only as root

Hi all,

I changed permissions in usr ubuntu folder and now I can`t start the system in graphic interface but only as a root. I know this is very difficult to fix, and now I’m tempted to reinstall ubuntu as in this link Install Ubuntu 18.04 with Lambda Stack from scratch - Technical Help - DeepTalk - Deep Learning Community Does anyone know if Jupyter notebook is installed in Lambda Stack installation by default? Previously it was there when we purchased the computer, not sure if this time is gonna work in the same way.