If you want to install on OpenShift I found this to make it easier....
https://github.com/ahwayakchih/openshift-nodebb
...works great and even comes with instructions on updating and managing plugins, very helpful.
The redis cart it points to is out of date, so try this one...
https://github.com/transformatordesign/openshift-redis-cart
...that will get you 2.8.x. If you want 3.x your going to have to look around. That one pointed to by jarey is broken. Theres a pull request to fix it and I forked the fix to here....
https://github.com/PAEz/openshift-redis-cart
...so I can use it while I wait for the other to be fixed (hope he fixes it, its linked to all over the place concerning installing nodebb on openshift).