https://blog.wongcw.com/2019/09/19/rhel-6%e5%92%8ccentos-6%e5%88%86%e6%94%af%e8%bf%8e%e4%be%86%e9%87%8d%e8%a6%81linux%e5%85%a7%e6%a0%b8%e5%ae%89%e5%85%a8%e6%9b%b4%e6%96%b0/