http://www.cnblogs.com/MoShin/archive/2012/04/25/2469156.html
当我们在虚拟机里安装lixunx系统，避免不了的要安装增强功能，无论是视觉效果还是物理机与虚拟机共享文件都是需要安装增强功能的。当我们在进入虚拟系统安装增强程序时可能会出现如下状态：
[root@localhost VBOXADDITIONS_4.1.12_77245]# sh ./VBoxLinuxAdditions.run（增强程序）
VirtualBox Guest Additions installer
Removing installed version 4.1.10 of VirtualBox Guest Additions...
Removing existing VirtualBox DKMS kernel modules [确定]
Removing existing VirtualBox non-DKMS kernel modules [确定]
Building the VirtualBox Guest Additions kernel modules
The headers for the current running kernel were not found. If the following
module compilation fails then this could be the reason.
The missing package can be probably installed with
yum install kernel-devel-2.6.18-238.el5
Not building the VirtualBox advanced graphics driver as this Linux version is
too old to use it.
Building the main Guest Additions module [失败]
(Look at /var/log/vboxadd-install.log to find out what went wrong)
Doing non-kernel setup of the Guest Additions [确定]
Installing the Window System drivers
Installing X.Org 7.1 modules [确定]
Setting up the Window System to use the Guest Additions [确定]
You may need to restart the hal service and the Window System (or just restart
the guest system) to enable the Guest Additions.
Installing graphics libraries and desktop services componen[确定]
/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。 停止。
Creating user for the Guest Additions.
Creating udev rule for the Guest Additions kernel module.
从上面的结果我们可以很清楚的看出来出现了一处错误，根据提示查看/var/log/vboxadd-install.log文件会有下面的错误：
[root@localhost VBOXADDITIONS_4.1.12_77245]# cat /var/log/vboxadd-install.log
/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。 停止。
Creating user for the Guest Additions.
Creating udev rule for the Guest Additions kernel module.
通过上面的提示我们可以知道错误的原因是没有内核原文件
解决方法如下：（下面的操作都是在虚拟电脑里进行的不要理解成在物理机里）
一；先安装下面的程序； gcc kernel kernel-devel
程序说明
gcc.i686 : 各类编译器（C、C++、Objective-C、Java, ...）
kernel.i686 : Linux 内核（Linux 操作系统的核心）
kernel-devel.i686 : 用来构建与内核匹配的内核模块的开发软件包。
程序安装
[root@localhost VBOXADDITIONS_4.1.12_77245]#yum instal gcc.i686 kernel.i686 kernel-devel.i686
（用yum安装时最好先用yum search 搜索下相应的程序,不同的版本可能会有不一样的后缀如有的可能是.i386）
二；重新启动电脑，启动时系统会自动从新的内核文件选项启动不要改回到原来的选项默认就好了（回到原来的选项还会出现上面的错误）。从新安装增强程序问题可以解决。