Ubuntu – How is a login via an ssh private/public key associated with a given user

ssh

I've created the private/public key pair using ssh-keygen. I installed the public as described in https://help.ubuntu.com/community/SSH/OpenSSH/Keys

And it works without a password, as expected – but only when logging in to root. Logging in directly as root is obviously a bad idea.

But the question is, how is that key pair associated or restricted to a given userid? I wouldn't expect a user to be able to log into ANY account on a system simply by virtue of having the public key installed on a host…

Best Answer

The command:

ssh-copy-id  username@host

As documented in the link above does not work from mac. Therefore, I logged in as root and of course, that is where the key was installed.

The answer seems to be: If You log in as the user, then cat the public key to the ~/.ssh/authorized_keys file.