搭建opensack时原生的源不好使就换了个阿里云的源试试
百度搜到的方法：https://blog.csdn.net/chavo0/article/details/51939362
1.备份
1 # mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
2.下载阿里云的源
# wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
3.运行yum makecache生产缓存
1 # yum makecache