yum install git -y无法安装找不到镜像

http://mirrors.163.com/centos/6/os/x86_64/repodata/repomd.xml: [Errno 14] PYCURL ERROR 22 - "The requested URL returned error: 404 Not Found" 尝试其他镜像。

cd /etc/yum.repos.d
vim CentOS-Base.repo
:%s/$releasever/7/g  
yum clean all 
yum makecache