Read about SSH here.

To be able to login as root via SSH, we need to change one line in this config file:

/etc/ssh/sshd_config

In the file, you will find following line:

  #PermitRootLogin prohibit-password
    

To allow logging in as root, we will uncomment the line and change "prohibit-password" to "yes". Like this:

  PermitRootLogin yes
    

Save the file and exit your editor. The last thing left to do: Restarting the SSH system service.

  # systemctl restart ssh