运行
sh ./VBoxLinuxAdditions.run
时FAILED，查看日志：
/tmp/vbox.0/Makefile.include.header:97: *** Error: unable to find the sources of your current Linux kernel. Specify KERN_DIR=<directory> and run Make again. Stop. Creating user for the Guest Additions. Creating udev rule for the Guest Additions kernel module.
意思是说没有内核源文件，解决的办法是运行
yum instal gcc.i686 kernel.i686 kernel-devel.i686
reboot
分别是编译器，内核，内核头文件以及Makefile，然后再重启，让系统从新的内核文件选项启动。再运行
sh ./VBoxLinuxAdditions.run
就可以编译成功了。
unable to find the sources of your current Linux kernel.
原文：http://www.cnblogs.com/mstk/p/6505457.html