Secure File Transfer Protocol (SFTP) is a great tool for performing secure file transfers. There is a command-line client, but users will most likely use a graphical client, such as Filezilla. A common use-case for SFTP is to allow website owners to upload web content files to the proper content directories on a web server. With a default SSH setup, anyone who has a user account on a Linux machine can log in through either SSH or SFTP, and can navigate through the server's entire filesystem. What we really want for SFTP users is to prevent them from logging into a command-prompt via SSH, and to confine them to their own designated directories.
With the exception of the slight difference in user-creation commands, this procedure works the same for either CentOS or Ubuntu. So, you can use either one of your virtual machines to follow along. We'll begin by creating an sftpusers group.
sudo groupadd...