centos7执行yum命令时报：Could not resolve host: mirrorlist.centos.org；未知错误-解决方案：

切换阿里云镜像源。

1.备份之前镜像源

mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup

2.下载新的 CentOS-Base.repo 到 /etc/yum.repos.d/

centos7

wget -O /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-7.repo

或者

curl -o /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-7.repo

3.运行命令生成缓存

yum makecache