配置国内yum源

配置中科大yum源，参考：

Centos镜像使用帮助 https://lug.ustc.edu.cn/wiki/mirrors/help/centos

EPEL镜像使用帮助 https://lug.ustc.edu.cn/wiki/mirrors/help/epel

以下整理了centos6的脚本（curl命令下载不了，自己手动下载）

Centos镜像使用帮助

cd /etc/yum.repos.d
mv -f /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.save
curl -o CentOS-Base.repo https://lug.ustc.edu.cn/wiki/_export/code/mirrors/help/centos?codeblock=2
rpm -Uvh http://download.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm
mv /etc/yum.repos.d/epel.repo /etc/yum.repos.d/epel.repo.save
mv /etc/yum.repos.d/epel-testing.repo /etc/yum.repos.d/epel-testing.repo.save
curl -o epel-testing.repo https://lug.ustc.edu.cn/wiki/_export/code/mirrors/help/epel?codeblock=1
curl -o epel.repo https://lug.ustc.edu.cn/wiki/_export/code/mirrors/help/epel?codeblock=0
rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-6
yum makecache