Thanks for your clarification, and apologies for the confusion. I think there was a misunderstanding about what I am trying to achieve.
I am not trying to bypass FOG or do something outside of FOG — quite the contrary. I am actively using FOG to deploy images to a fleet of Raspberry Pi devices.
My previous confusion came from the fact that my test units kept landing in the interactive FOG debug mode (requiring pressing Enter to get a prompt), which led me down the wrong path thinking I needed a manual workaround. My ultimate goal is simply to have a standard, fully automated deployment task (non-debug) run seamlessly on the Raspberry Pis without requiring manual intervention at each boot.
I will look into standard deployment tasks and post-init scripts as you suggested. Thanks for pointing me in the right direction!