使用国内的阿里云镜像
（1）把/etc/yum.repos.d/下面所有的源给删除掉了
（2）base源
1 # CentOS 5 2 wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-5.repo 3 # CentOS 6 4 wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo 5 # CentOS 7 6 wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
（3）epel源
# epel(RHEL 7) wget -O /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-7.repo # epel(RHEL 6) wget -O /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-6.repo # epel(RHEL 5) wget -O /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-5.repo