When working on automated bare-metal provisioning of Kubernetes clusters (the main purpose of the repo https://github.com/kinvolk/racker) it's quite time consuming to test on actual hardware. Also, the hardware may be in use at the moment, or you don't even have access to a free full rack. It was nice to see that there is IPMI support for QEMU and that ipmi_sim integrates well, but it was quite hard to set up. Especially the requirement that the BMCs should get their IP address via DHCP on the internal network is a bit more complicated/hacky. If you need to test IPMI commands or develop your own IPMI automation, have a look at this, otherwise it may serve as a demo on how to do Immutable Infra with your on-prem servers.