今天服务器当机，重启后发现ftp无法使用.
[root@localhost ~]# ps -ef|grep ftp
test1     3112  3111  0 16:32 ?        00:00:00 /usr/libexec/openssh/sftp-server
user1      3358  3357  0 16:39 ?        00:00:00 /usr/libexec/openssh/sftp-server
果然ftp服务没有启动．
[root@localhost ~]# netstat -tuln
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address               Foreign Address             State
tcp        0      0 0.0.0.0:3306                0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:21                  0.0.0.0:*                   LISTEN
tcp        0      0 127.0.0.1:25                0.0.0.0:*                   LISTEN
tcp        0      0 127.0.0.1:6010              0.0.0.0:*                   LISTEN
tcp        [...]