This page is great https://maas.io/how-it-works
In the “life cycle” section, it was not immediately clear to me how MAAS transitions a server between states. I figured out that MAAS essentially intervenes during the boot process, and depending on the recorded state of the machine in it’s database, will take different actions. For example, for a machine to deploy, it will need to be rebooted if it is already running something else. To do that, MAAS will use e.g. IPMI to reboot the machine, and then intercept it while booting in order to deploy a new image.
Although it might be obvious to some, I think it is not to all - and it did take me a little while to figure out this was a central tenet as to how MAAS works. It would be great if we could add some words around this, perhaps even a small “day in the life” of a server transitioning between some of these states and what happens at each stage.