For CentOS 7, ensure that the system has the correct Linux kernel sources from the CentOS repositories: $ sudo yum install -y kernel-devel-$(uname -r) kernel-headers-$(uname -r) Update the repository cache and install the driver using the nvidia-driver-latest-dkms meta-package. Turn on and install EPEL Repo on a CentOS 7.x You must install dkms for registering the NVIDA kernel module with DKMS: $ sudo yum -y install epel-release $ sudo yum -y install dkms.
Has being a while but I am back...Installing dkms on CENTOS 6.. it is easy ... just find the package you need download and install.
root@ip-172-30-0-42 ec2-user]# wget http://linux.dell.com/dkms/permalink/dkms-2.2.0.3-1.noarch.rpm
--2014-07-14 16:20:50-- http://linux.dell.com/dkms/permalink/dkms-2.2.0.3-1.noarch.rpm
Resolving linux.dell.com... 143.166.224.62
Connecting to linux.dell.com|143.166.224.62|:80... connected.
HTTP request sent, awaiting response... 200 OK
Install Virtualbox Additions On Centos 7 Guest Vm
Length: 108241 (106K) [application/octet-stream]Saving to: “dkms-2.2.0.3-1.noarch.rpm”
Installing Dkms On Centos
100%[>] 108.241 457K/s in 0,2s 
2014-07-14 16:20:50 (457 KB/s) - “dkms-2.2.0.3-1.noarch.rpm” saved [108241/108241][root@ip-172-30-0-42 ec2-user]# rpm -i dkms-2.2.0.3-1.noarch.rpm
Installing Dkms On Centos 7 5
[root@ip-172-30-0-42 ec2-user]#Installing Dkms On Centos 7 2
Installing Dkms On Centos 7 Command
.Enjoy