Change password without root access

Hello,

I am using a Jetson Tegra. I can log in via SSH (and without being asked to fill in the password).
The password I used to fill in doesn’t work anymore. Which means I have access to the folders, can execute and compile some scripts but have no root access anymore.
I cannot either have access to the log file to see what happened with other users on this Jetson.
Does anyone can help on how to get back root access? and how to change the password?

Thank you very much,

If the system was accessible to the outside world over the internet, and not isolated via firewall or a router, then it was probably hacked and needs to be flashed. Otherwise, it’d be very odd that the password no longer works.

FYI, a clone of the root partition can be created and loopback mounted, then inspected, edited, and used as a file system for reflash after the edits. This would include replacing passwd and shadow files. I would strongly recommend against simply editing the password if there is any chance someone on the outside had access to it, as there could be other malicious changes. A clone would give you an ability to save what is there now and do a fresh flash followed by restore piece by piece of what you are interested in. For clone, see:
http://elinux.org/Jetson/Cloning