https://blog.wongcw.com/2018/10/12/vps-%e7%8b%ac%e7%ab%8b%e6%9c%8d%e5%8a%a1%e5%99%a8%e5%9c%a8%e5%91%bd%e4%bb%a4%e8%a1%8c%e4%b8%8b%ef%bc%8c%e5%8d%87%e7%ba%a7ubuntu-14-04-%e5%88%b0-ubuntu16-04/