更换阿里云yum源和epel源（1）yum源一、备份原yum源mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup二、下载新的CentOS-Base.repo 到/etc/yum.repos.d/CentOS 5wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-5.repoCentOS 6wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repoCentOS 7wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo三、清除yum缓存，重新生成缓存yum clean allyum makecache（2）epel源一、备份(如有配置其他epel源)mv /etc/yum.repos.d/epel.repo /etc/yum.repos.d/epel.repo.backupmv /etc/yum.repos.d/epel-testing.repo /etc/yum.repos.d/epel-testing.repo.backup二、下载新repo 到/etc/yum.repos.d/epel(RHEL 7)wget -O /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-7.repoepel(RHEL 6)wget -O /etc/yum.repos.d