https://blog.csdn.net/vchen_hao/article/details/53925082
https://www.itzgeek.com/how-tos/linux/centos-how-tos/install-and-configure-vsftpd-on-centos-7-rhel-7.html
Install and Configure FTP server on CentOS 7 / RHEL 7 – (vsftpfd)