Here’s the way I execute rake command in OpenShift server in.
Environment
My OpenShift Server is using ruby 2.0.
Procedure
Login to your OpenShift server. I logged in with rhc ssh
(reference: OoenShift: ssh login).
Then, setup enviroments and execute your rake task.
Actually, I’m not sure that source ${OPENSHIFT_CARTRIDGE_SDK_BASH}
is really needed.