How to deny access to other directories?

Question

System administration

Good day. I apologize for such a "noob question", but unfortunately I could not google it.
There is a vps, ubuntu with lamp, created an admin user, changed its root directory to /var/www.
I log in as admin via putty, initially opens /var/www, but if I change the directory, for example, cd /etc, then he calmly changes it. How to disable output above the /www directory?
Thanks in advance for your reply!

Answer 1

If you want it to be unable to go anywhere, then you need to use chroot. So, no one usually forbids users to go to / etc, sometimes it is even useful.

Answer 2

How did you create the user?
Most likely you have added him to the admin group and it is not surprising that he has rights.
File ownership is changed with
chown File permissions
are changed with
chmod