centos7配置阿里云yum源

# wget下载
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
# curl下载（如果yum安装wget失败的话用curl）
curl -o /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo

然后将repo文件中的$releasever全部替换为7