vsftpd-3.0.0 made the listen mode default. In order to maintain backward compatibility, default /etc/vsftpd.conf in SUSE contains listen=NO listen_ipv6=YES if you plan to use xinetd (/etc/xinetd.d/vsftp) you don't need to change anything by default, but if you have ipv6 available you have to set listen_ipv6=NO too in order for xinetd to work. Alternatively you can also use systemd socket service that listens on port 21 and starts the server like xinetd would. This service does not require you to change ANY variable in the /etc/vsftpd.conf.