备份本地yum源文件
cd /etc/yum.repo.d/
mv CentOS-Base.repo CentOS-Base.repo.bakeup
下载国内yum源
阿里云yum源
wget http://mirrors.aliyun.com/repo/Centos-7.repo
163(网易)yum源
wget http://mirrors.163.com/.help/CentOS7-Base-16.repo
更新yun源
mv Centos-7.repo CentOS-Base.repo
yum clean all
yum makecache
yum update