CentOS7.x使用overlay文件系统

https://www.cnblogs.com/yufeng218/p/8370670.html

http://www.cnblogs.com/lehuoxiong/p/9908118.html

http://blog.51cto.com/foxhound/1773879

http://www.cnblogs.com/hahp/p/6519786.html