Centos7 yum安装时提示依赖包失败

1. 网速要有保证
2. 清缓存
   #yum clean all
   #yum makecache
   #yum update -y //升级软件和内核
3. 添加阿里云DNS
   DNS3=223.5.5.5
4. 更换reop源
   yum安装会从三个reop源（base、extras、updates）随机获取地址；
   #mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
   #yum -y install wget
   #wget -O /etc/yum. repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
   #yum clean all
   #yum makecache