= How is power managed in a dedicated server in a data center. How is it turned on? =

We have apps running in the application server which runs in a container which runs in a VM which runs on a host system. Now I really think that a host system needs HDD and SSD, but I've seen that computer can boot using ethernet ( for example freshly build ). So is there still a quitesystem above the supervisor? Can it be used to start and stop a server using commands sent over ethernet? Can it be used to place a fresh Supervisor image onto a dedicated server?
Google search only reveals that you should not turn on all servers at once after a power outage. So maybe it is okay that this Bios-network stuff (routers) are all turned on at once (heat capacity of all copper wires suffice to sustain the inrush into the electrolyte capacitors .. so only turn on after a cooldown) and the real computers and HDDs and SSDs are turned on using ethernet?
Maybe the power switch on each rack as an ethernet address? Maybe on power on each server tries too boot from a preconfigured IP address? Only if not found, it boots from disk? Though I think it is difficult to arrange VMs and containers in such a way that a whole rack can be powered down. Probably, nobody does this anyway. Cloud is about sharing and there are always more task which wait for the price to drop

For example, Dell PowerEdge servers have iDrac which allows remote management of power on and off, as well as bios (even without an OS) so in a way you could say it’s “above” the hypervisor
These typically have a separate Ethernet port for management which doesn’t connect to the same network as the NIC passed into a VM, which may go on a different switch or network entirely. This is called out of band management

This is in the realm of physical hardware, networking etc. It's a fairly specialised job

You may get the answer you're looking for on r/datacenter
Thanks. Partly I wanted to discuss the big picture for a dev. Like in this sub web devs praise kubernetes: you don’t need physical access

Edit: Wouldn't it be cool if this was normal and in-band. Kubernetes finds out that you container saturates a whole physical server. Then it loads a linux image on the server without hypervisor and unpacks the Docker imagewhere now the content runs like it did before it was packed. The IP address and port are the real IP address and port.