CentOS Linux version 7 is a free and open source operating system. It is a clone of Red Hat Enterprise Linux without dedicated support from Red Hat, Inc. CentOS is a popular choice for web hosting and other purposes.
OpenSSH is a free and open source implementation of SSH protocol. The SSH protocol is a method for secure remote login from your system to another system such as a CentOS Linux server. Secure Shell (SSH) is a cryptographic protocol for operating network services securely over an unsecured network such as LAN or WAN or Internet. Typically one can use SSH for transferring files, managing servers, remote login, remote command execution, uploading or downloading files, making backups and more.
Disabling root level access is a good idea for Linux and Unix-like operating system. One should only log in with public ssh key and avoid password based login. This page shows how to disable or enable root login in CentOS Linux 7 server and increase security of your server.
From the blog post:
We all know that CentOS comes with root access disabled for the outside world by default. This means that you can not directly log in as a root user via SSH, but you can still go ahead and utilize root privileges by using the ‘sudo’ command instead. However, sometimes it is more convenient to log in directly as the root user. That’s why in this article, we will talk about how to enable, disable and secure the SSH login to your server when attempting to log in as root. In order to disable the root login, we need to modify the main ssh configuration file “sshd_config” with a text editor of your choice. In our example, we will use nano as an editor.