Centos 7 使用yum安装软件包报错curl#6 - "Could not resolve host: mirrorlist.centos.org; 未知的错误"

[root@localhost yum.repos.d]# yum install wget 已加载插件：fastestmirror Loading mirror speeds from cached hostfile Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=7&arch=x86_64&