Disallow superusers and single-user mode in POSTGRESQL

I have a doubt about superusers and single-user mode. I want to restrict the access to a certain database, in a way that only those users which I gave privileges can see the structure of my database. To achieve that, I had to erase the superuser, since it bypasses all permission checks. But then I found that if I have access to the computer, I can enter in "single-user mode" and grant superuser privileges or even creating new users. ### My question Can I disallow permanently the use of superusers and single-user mode?