Nmap scan report for localhost (127.0.0.1)
Host is up (0.000086s latency).
PORT   STATE SERVICE VERSION
21/tcp open  ftp     vsftpd 3.0.3
Service Info: OS: Unix

Nmap scan report for localhost (127.0.0.1)
Host is up (0.000086s latency).
PORT   STATE SERVICE VERSION
21/tcp open  ftp
Service Info: OS: Unix

vi /etc/vsftpd/vsftpd.conf

ftpd_banner=Welcome to blah FTP service.