1、红帽8相当简单就可以完成： 从https://mirrors.aliyun.com/repo/Centos-8.repo下载阿里云源 将Centos-8.repo文件放到/etc/yum.repo.d/下。确保只有一个yum源 执行命令：yum clean all && yum makecache 完毕
2、红帽7比8稍麻烦： 查找并卸载已安装的yum：
1、 查询安装的yum：rpm –qa |grep yum 卸载已安装的yum源：rpm –qa |grep yum |xargs rpm –e –nodeps
1.wget https://mirrors.aliyun.com/centos/7/os/x86_64/Packages/yum-metadata-parser-1.1.4-10.el7.x86_64.rpm
2.wget https://mirrors.aliyun.com/centos/7/os/x86_64/Packages/yum-3.4.3-158.el7.centos.noarch.rpm
3.wget https://mirrors.aliyun.com/centos/7/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.31-45.el7.noarch.rpm
4.wget https://mirrors.aliyun.com/centos/7/os/x86_64/Packages/yum-utils-1.1.31-45.el7.noarch.rpm
5.wget https://mirrors.aliyun.com/centos/7/os/x86_64/Packages/python-urlgrabber-3.10-8.el7.noarch.rpm
安装rpm包：rpm –ivh *.rpm –-force - -nodeps 下载repo文件： wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo 修改Centos-7.repo文件将所有$releasever替换为7： vim /etc/yum.repos.d/CentOS-Base.repo :%s/$releasever/7/g 运行以下命令： yum clean all yum makecache