VirtualBoX安装增强功能报错解决方法

Building the main Guest Additions module
http://www.cnblogs.com/MoShin/archive/2012/04/25/2469156.html
sudo yum -y install gcc   kernel   kernel-devel

Building the OpenGL support module FAILED
http://it.oyksoft.com/post/6568/

VirtualBox Guest Additions on Fedora 18/17, CentOS/RHEL 6.4/5.9 http://www.if-not-true-then-false.com/2010/install-virtualbox-guest-additions-on-fedora-centos-red-hat-rhel/

How to Configure Environment Variables in Linux (CentOS)
http://www.tothetech.com/tips-tricks/how-to-configure-environment-variables-in-linux-centos.html