在docker容器內使用 yum 或者 wget 命令，會提示 cannot resolving host address 無法解析主機地址 ，也就是容器內無法解析DNS。
Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=os&infra=stock32 error was 14: curl#6 - "Could not resolve host: mirrorlist.centos.org; Unknown error" One of the configured repositories failed (Unknown), and yum doesn't have enough cached data to continue. At this point the only safe thing yum can do is fail. There are a few ways to work "fix" this: 1. Contact the upstream for the repository and get them to fix the problem. ..................................................................... 4. Configure the failing repository to be skipped, if it is unavailable. Note that yum will try to contact the repo. when it runs most commands, so will have to try and fail each time (and thus. yum will be be much slower). If it is a very temporary problem though, this is often a nice compromise: yum-config-manager --save --setopt=<repoid>.skip_if_unavailable=true
度娘找到一個方案，我在這里使用了其中的 1. 宿主機防火牆開啟偽裝IP功能 方案，解決了問題。
放上該博客： https://my.oschina.net/u/580483/blog/4264763/print