Here are the key steps:
1. Kill any existing controllers running on the system
2. Clear out any existing Mininet topology using mn -c
3. Start the Ryu OpenFlow controller by running:
ryu-manager --verbose ./simple_switch_13.py
This starts the Ryu controller with the simple_switch_13.py application, which provides basic OpenFlow switch functionality. The --verbose flag prints debug information from the controller. We have now initialized the SDN environment with Ryu acting as the controller.