1.关闭禁用防火墙和selinux

systemctl disable firewalld --now
sed -i 's/SELINUX=enforcing/SELINUX=disabled/' /etc/selinux/config

2.保证可以连接外网

 ping -c3 www.baidu.com

3.配置yum为阿里仓库并下载epel源

mkdir /etc/yum.repos.d/bak/; mv /etc/yum.repos.d/*.repo /etc/yum.repos.d/bak/

wget -O /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-7.repo

 yum -y install epel-release.noarch

#查看仓库是否有rpm包

 yum repolist