I enabled logging to my remote Kubuntu computer with a public/private key following this short tutorial, and now logging is easy and doesn't ask for password.
Anyway, I noticed when I try to sudo, I'm asked for a password and when entered it says it's incorrect. And since I cannot sudo, I cannot modify the sshd_config or other root files.
I even cannot login to the physical machine using my own password, so all in all, I'm stuck.
How do I enable back the password authentication? (knowing that I cannot use sudo now) Thanks.