在sels10机器上登入ftp输入用户名和密码之后再ls发现出现如下问题Entering Extended Passive Mode
ftp> ls
229 Entering Extended Passive Mode (|||51374|)
要解决这种情况，ctrl+c后输入epsv4 off回车即可。
ftp> epsv4 off
EPSV/EPRT on IPv4 off.
ftp> ls
227 Entering Passive Mode (9,44,51,77,147,2).
150 Opening ASCII mode data connection for file list
drwxr-xr-x 2 root system 256 Jul 28 22:21 dev
起初在网上搜说是passvie mode的问题，输入passive之后结果如下：
ftp> passive
Passive mode: off; fallback to active mode: off.
ftp> ls
200 EPRT command successful
ftp最基本命令：
ftp 121.42.x.x
open 121.42.x.x
cd xxxx
put xxx xxx