【Yum报错】Could not resolve host: mirrorlist.centos.org； Name or service not known

解决这个问题最简单的办法是重新安装Yum源，一次到位，避免无效尝试。

1.备份系统自带的yum源配置文件

mkdir /root/yum_backup;
cp /etc/yum.repos.d/* /root/yum_backup/;

2.卸载yum

2.1 反查yum安装

rpm -qa yum

2.2 卸载yum包

rpm -qa | grep yum | xargs rpm -e --nodeps;
rpm -qa yum;

3.安装yum

3.1 随便找个文件夹，以/opt/software为例，下载最新的rpm包

cd /opt/software;
wget http://mirrors.aliyun.com/centos/7/os/x86_64/Packages/yum-3.4.3-168.el7.centos.noarch.rpm; 
wget http://mirrors.aliyun.com/centos/7/os/x86_64/Packages/yum-metadata-parser-1.1.4-10.el7.x86_64.rpm;
wget http://mirrors.aliyun.com/centos/7/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.31-54.el7_8.noarch.rpm;

3.2 删除/etc/yum.repos.d/目录下内容

rm -rf /etc/yum.repos.d

3.3 安装阿里云的yum源

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

3.4 清除yum缓存及新建缓存

yum clean all;
yum makecache;