Allowing SSH remote login from root user is dangerous for your Linux server. So when you install a server you first need to disable root login for securing your server from brute force attack. Instead of allowing root user for ssh you can allow another hidden local user for remote login.
Login from root user
Edit SSH config file and chnage PermitRootLogin Yes to no
# vim /etc/ssh/sshd_config
#PermitRootLogin yes
PermitRootLogin no
Restart SSH service
# service sshd restart