How to Enable root login over SSH?

1. First login as a root user.
2. Then edit the sshd_config file by provided command which is in /etc/ssh/sshd_config Directory  

nano /etc/ssh/sshd_config

3. Now add a line in the Authentication section of the file that says PermitRootLogin yes. In some cases, this line may already exist and started with a "#". In this case, remove the "#" from start like given below.

# Authentication:

#LoginGraceTime 2m

PermitRootLogin yes

#StrictModes yes

#MaxAuthTries 6

#MaxSessions 10

4. After that save the changes that you have made in upper step /etc/ssh/sshd_config file.
5. In the end Restart the SSH server by given command to apply changes.

service sshd restart

You can now connect to the server as root over SSH.