linux 目錄結構說明

引用網址：

1. http://linux.vbird.org/linux_basic/redhat6.1/linux_05file.php
2. http://jashliao.pixnet.net/blog/post/161938997-%E6%AF%8F%E5%A4%A9%E4%B8%80%E5%80%8Blinux%E6%8C%87%E4%BB%A4--linux%E7%9B%AE%E9%8C%84%E7%B5%90%E6%A7%8B