备份yum源
cd /etc/yum.repos.d
mkdir repo_bak
mv *.repo repo_bak/
下载阿里云repo文件
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
wget -O /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-7.repo
清空yum缓存并且生成新的yum缓存
yum clean all
yum makecache
安装软件扩展源
yum install -y epel-release
查看更换的源
yum repolist
安装nginx
yum install nginx
启动
systemctl start nginx
网页查看
在浏览器上输入阿里云你自己服务器的ip地址，访问即可，如下表示启动成功