Arturito.net

1. Login as root

2. Install OpenSSH by running command:

apt-get install ssh

3. open file /etc/ssh/sshd_config and add these values:

#Authentication
PermitRootLogin no
MaxAuthTries 2

First one blocks access for root, so then you can login with a standard account and hit su to switch to the root user. Second one disconnects from the session after two failed login attempts.

You can also add this line:

AllowUser   your_username

It allows only specified user to log in using ssh. After logging in as a standard user just su and you have all root privileges.