Create a CentOS 7 VM:
mkdir centos7
cd centos7
vagrant init madorn/centos7
vagrant up
vagrant ssh
Follow Centos 7 directions.
Copy make_universe.sh
, modify the included packages if necessary (current list is ~10-11GB).
chmod 755 make_universe.sh
sudo -s
./make_universe.sh
This process will take some time.