https://blog.wongcw.com/2018/08/02/%e5%9c%a8centos7%e4%b8%8a%e6%89%8b%e5%8a%a8%e9%87%8a%e6%94%be%e5%86%85%e5%ad%98cache%e5%92%8c%e8%84%9a%e6%9c%ac%e5%ae%9a%e6%97%b6%e9%87%8a%e6%94%be/