Vsftpd

modprobe ip_conntrack_ftp

Resources
https://www.digitalocean.com/community/tutorials/how-to-configure-vsftpd-to-use-ssl-tls-on-an-ubuntu-vps
 * https://www.digitalocean.com/community/tutorials/how-to-set-up-vsftpd-on-ubuntu-12-04
 * https://help.ubuntu.com/community/vsftpd
 * http://manpages.ubuntu.com/manpages/quantal/man5/vsftpd.conf.5.html