====== Install vsftpd on Ubuntu ======
  * apt install vsftpd
  * edit /etc/vsftpd.conf
      * local_enable=YES
      * local_umask=022
      * write_enable=YES
      * chroot_local_user=YES
      * allow_writeable_chroot=YES
      * pasv_enable=Yes
      * pasv_min_port=40000
      * pasv_max_port=40100
  * service vsftpd restart