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From a command line use the following:

Render -r rmanrenderman sceneFile

It is also possible to only generate RIB without subsequently rendering.

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A complete list of the options can also be seen by running:

Render -r rmanrenderman -h

If you get a warning like the following, you need to put rmanRenderer.xml and ribRenderer.xml from the RenderMan for Maya installation in a place where Maya can find it.

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There are some files in the directory that aren't RIB files.  What are those?

The RLF file contains user made RLF files (assigned for GPU archives) contain material and binding information.  Materials are injected into the RIB file by a RIF at render time.

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