我在运行 Ubuntu Linux 14.04 的服务器上安装了 ProFTPd 服务。我不知道为什么 ProFTPd 会自行关闭。我有足够的 RAM 和 CPU，但我真的不知道为什么会发生这种情况。我还检查了 ProFTPd 配置文件，但我仍然不明白。
# /etc/proftpd/proftpd.conf -- This is a basic ProFTPD configuration file.
# To really apply changes, reload proftpd after modifications, if
# it runs in daemon mode. It is not required in inetd/xinetd mode.
#
# Includes DSO modules
Include /etc/proftpd/modules.conf
# Set off to disable IPv6 support which is annoying on IPv4 only boxes.
UseIPv6 on
# If set on you can experience a longer connection …