Mar 16 12:05:46 yan-laptop proftpd[15868] yan-laptop: ProFTPD 1.3.3g (maint) (built Fri Mar 16 2012 10:36:06 CST) standalone mode STARTUP
Mar 16 12:05:46 yan-laptop proftpd[15819] yan-laptop (yan-laptop[::ffff:127.0.0.1]): FTP session closed.
Mar 16 12:05:52 yan-laptop proftpd[15877] yan-laptop (yan-laptop[::ffff:127.0.0.1]): FTP session opened.
Mar 16 12:05:57 yan-laptop proftpd[15877] yan-laptop (yan-laptop[::ffff:127.0.0.1]): ftp: Directory /home/ftp/ is not accessible.
Mar 16 12:07:39 yan-laptop proftpd[15877] yan-laptop (yan-laptop[::ffff:127.0.0.1]): FTP session closed.
Mar 16 12:11:00 yan-laptop proftpd[15868] yan-laptop: ProFTPD killed (signal 15)
Mar 16 12:11:00 yan-laptop proftpd[15868] yan-laptop: ProFTPD 1.3.3g standalone mode SHUTDOWN
解决方法：
去掉aclUSE标记，重新编译proftpd安装
USE="-acl" emerge proftpd
重启服务后问题解决。