Redhat 7 yum源换成centos的YUM 源

详细步骤：

卸载yum

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

再次查看是否删除完成

[root@localhost yum.repos.d]# rpm -qa |grep yum

安装下载的软件包

wget https://mirrors.aliyun.com/centos/7/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.31-50.el7.noarch.rpm

wget https://mirrors.aliyun.com/centos/7/os/x86_64/Packages/yum-metadata-parser-1.1.4-10.el7.x86_64.rpm

wget https://mirrors.aliyun.com/centos/7/os/x86_64/Packages/yum-3.4.3-161.el7.centos.noarch.rpm

wget https://mirrors.aliyun.com/centos/7/os/x86_64/Packages/yum-utils-1.1.31-50.el7.noarch.rpm 

wget https://mirrors.aliyun.com/centos/7/os/x86_64/Packages/yum-updateonboot-1.1.31-50.el7.noarch.rpm

wget https://mirrors.aliyun.com/centos/7/os/x86_64/Packages/python-iniparse-0.4-9.el7.noarch.rpm

wget https://mirrors.aliyun.com/centos/7/os/x86_64/Packages/python-urlgrabber-3.10-9.el7.noarch.rpm

如果版本号不对，请大家自行https://mirrors.aliyun.com/centos/7/os/x86_64/Packages/查找对应rpm，更换版本。

之后就是直接安装 rpm -ivh yum-*

之后发现提示有问题

后来发现是python-urlgrabber和rpm版本过低；所以可以去下载的版本的，或者直接更新

wget http://mirrors.163.com/centos/7/os/x86_64/Packages/rpm-4.11.3-35.el7.x86_64.rpm
wget http://mirrors.163.com/centos/7/os/x86_64/Packages/python-urlgrabber-3.10-9.el7.noarch.rpm
然后更新
rpm -Uvh rpm-4.11.3-35.el7.x86_64.rpm --nodeps
rpm -Uvh python-urlgrabber-3.10-9.el7.noarch.rpm --nodeps

然后再次执行rpm -ivh yum-*

查看是否安装好以上rpm包，rpm -qa |grep yum

去阿里镜像站下载centos-7.repo
CentOS 7

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

vim /etc/yum.repos.d/CentOS-Base.repo
把releasever替换成现有系统的版本号(7)
vim替换命令
：%s/$releasever/7/g

最后执行 yum clean all 清除缓存