[all variants] init, init.d, upstart.. trying to understand.

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http://ubuntuforums.org – I'm fairly new to Linux still, and I'm finding the subject of the history of how Linux managed, and now manages initialization. I've read all kinds of sources ,and I understand that the init system has moved from the older V system..to a few others and now is using upstart. But it's still a confusing mess in my head. Is this subject something critical to learn right away? And are there any older distros I can install into a VM to experiment with the older system which used init and the inittab file? I just feel like I need to go back to the roots and learn that first, before I can understand (Hardware)