virtualbox安装增强功能报错：
vboxadd.sh failed modprobe vboxguest failed.
解决方法：
yum install dkms binutils gcc make patch libgomp glibc-headers glibc-devel kernel-headers
then
yum install kernel-devel
or
yum install kernel-PAE-devel
Then
re-run VBoxLinuxAdditions.run.