1.备份旧的配置文件
cd /etc/yum.repos.d
mv CentOS-Base.repo CentOS-Base.repo.bak
2.下载阿里源的文件
sudo wget -O CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
3.更新yum重建缓存
yum clean all
yum makecache
cd /etc/yum.repos.d
mv CentOS-Base.repo CentOS-Base.repo.bak
sudo wget -O CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
yum clean all
yum makecache