如果找不到ifconfig
yum install net-tools
切换阿里的yum源

1、备份之前的仓库文件

mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.back

2、下载阿里云的仓库文件

curl -o /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo

3、革除缓存

yum clean allyum makecache