1、
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/
CentOS 7
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
CentOS 8
进入yum.repos.d目录
1.cd /etc/yum.repos.d
备份3个源文件
cp CentOS-Base.repo CentOS-Base.repo.bak
cp CentOS-AppStream.repo CentOS-AppStream.repo.bak
cp CentOS-Extras.repo CentOS-Extras.repo.bak
修改3个文件中的地址：
sed -i 's/mirrorlist=/#mirrorlist=/g' CentOS-Base.repo CentOS-AppStream.repo CentOS-Extras.repo
sed -i 's/#baseurl=/baseurl=/g' CentOS-Base.repo CentOS-AppStream.repo CentOS-Extras.repo
sed -i 's/http:\/\/mirror.centos.org/https:\/\/mirrors.aliyun.com/g' CentOS-Base.repo CentOS-AppStream.repo CentOS-Extras.repo
3、之后运行yum clean all 清空缓存,运行yum makecache生成缓存
yum clean all
yum makecache
