更换yum为阿里云

备份原来的yum源mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup

设置yum源为阿里云wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo

添加epel源wget -P /etc/yum.repos.d/ http://mirrors.aliyun.com/repo/epel-7.repo

清理缓存并生成新的缓存

yum clean all

 yum makecache