通过root身份登录,进行接下来的配置

添加用户组、添加用户

groupadd ftpusers
useradd -d /mnt/site/site1 -g ftpusers -s /sbin/nologin weba
passwd weba
useradd -d /mnt/ftp -g ftpusers -s /sbin/nologin webb
passwd webb

修改配置文件  proftpd.conf

DefaultRoot ~
<Directory "/mnt/site/site1/">
    <Limit ALL>
        AllowUser weba
        DenyALL
    </Limit>
    <Limit CWD READ RETR DIRS>
        AllowALL
    </Limit>
</Directory>

<Directory "/mnt/ftp/">
    <Limit ALL>
        AllowUser webb
        DenyALL
    </Limit>
    <Limit CWD READ RETR DIRS>
        AllowALL
    </Limit>
</Directory>

参考:
http://blog.fens.me/linux-ftp-proftpd/
http://blog.csdn.net/sin90lzc/article/details/7525670