VM下LINUX完美增加/扩展硬盘空间（LVM）

参考：

http://blog.chinaunix.net/uid-591075-id-2732280.html

http://www.reistlin.com/blog/18

https://www.cnblogs.com/bitter-first-sweet-last/p/6638634.html

https://blog.csdn.net/coolJoezhou/article/details/79090006

https://www.2cto.com/net/201608/541676.html