检查您的 /var/log/messages 是否有来自 proftpd 的错误。
这是我的 /var/log/messages 用于简单的 FTP 会话:
Jan 16 16:39:15 localhost xinetd[577]: START: ftp pid=9317 from=::ffff:10.50.2.4
Jan 16 16:39:16 localhost proftpd[9317]: 10.52.52.203 (10.50.2.4[10.50.2.4]) - FTP session opened.
Jan 16 16:39:16 localhost proftpd[9317]: 10.52.52.203 (10.50.2.4[10.50.2.4]) - FTP session closed.
Jan 16 16:39:16 localhost xinetd[577]: EXIT: ftp status=0 pid=9317 duration=1(sec)
Jan 16 16:39:16 localhost xinetd[577]: START: ftp pid=9318 from=::ffff:10.50.2.4
Jan 16 16:39:16 localhost proftpd[9318]: 10.52.52.203 (10.50.2.4[10.50.2.4]) - FTP session opened.
Jan 16 16:39:22 localhost proftpd[9318]: 10.52.52.203 (10.50.2.4[10.50.2.4]) - Preparing to chroot to directory '/var/www/vhosts/domain.tld'
Jan 16 16:40:03 localhost xinetd[577]: Exiting...