Installing Ubuntu Server 18.04, I see the networking config in /etc/netplan has a .yml file that talks about CloudInit and networking configuration not persisting across instances.
I have read https://help.ubuntu.com/community/CloudInit but am unsure what the exact use case for CloudInit would be, and why it would be on by default. My server is not on AWS nor any cloud platform.
So I've disabled this with /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg as per the comment at the start of the config file, and assigned a simple static IP and that works fine.
To be clear: I am not asking how to disable it (I have done that, and am happy with the result). I just don't understand the reason for its existence, nor can I make that out from the documentation for it. Is it intended to replace DHCP in some way?