Update and install dependencies
yum -y update kernel*
reboot -r now
yum install -y gcc kernel-devel kernel-headers dkms make bzip2 perl
export KERN_DIR=/usr/src/kernels/`uname -r`
or Install dependencies
# sudo yum groupinstall “Development Tools”
# sudo yum install kernel-devel
Mount the Virtualbox Additions CD ISO
# su –
# mkdir /media/cdrom/
# mount /dev/cdrom /media/cdrom/
# cd /media/cdrom/
# ./VBoxLinuxAdditions.run
# yum install VirtualBox-4.1
https://wiki.centos.org/HowTos/Virtualization/VirtualBox
https://www.gaggl.com/2014/07/install-virtualbox-additions-on-centos-7-guest-vm/