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When searching the internet for UEFI, I found two types of articles: one type "explains" to me that UEFI is the modern alternative to MBR booting, that it's widely supported by now and that I should probably use it. The other type of articles offers step by step instructions to solve a very specific problem. I couldn't find an article though explaining the concepts of UEFI.

Some questions that come to mind:

So far I understand that there is a small EFI partition that plays a key role. But what does it actually contain and what does it do? Not necessarily down to the last file, but a general overview.

In the BIOS I can see UEFI boot entries. How does the BIOS know about them? Are these saved to the BIOS on installation? Or does the BIOS scan the EFI partition on boot?

In a multi OS environment it seems that there is a EFI partition on every disk with an operating system. Does every operating system need its own EFI partition, or can different OS's share the same EFI partition?

user1785730
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  • I'm gonna give this a +1 because it is a mind-numbingly confusing paradigm, most of which no consumer would ever need to know. Bear in mind though that any answer is only going to skirt the broadest sense, as your question is too global for real specifics, & contains some elements of misunderstanding. – Tetsujin Mar 03 '21 at 19:18
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    We have a lot of specific questions on this rather broad topic so it might be worth using the search tool and the "related questions" areas of individual questions: [How do the 'EFI system partition' and UEFI *.efi files relate?](https://superuser.com/questions/388584) and [How does EFI find bootloaders?](https://superuser.com/questions/731362) and [UEFI detection (ESPs)](https://superuser.com/questions/976770) and [What exactly is “UEFI with CSM” boot mode?](https://superuser.com/questions/1284392) and [Where is the UEFI boot order stored?](https://superuser.com/questions/955525) – Mokubai Mar 03 '21 at 20:06
  • I think I would've accepted a link to [this article](https://www.happyassassin.net/posts/2014/01/25/uefi-boot-how-does-that-actually-work-then/) as an answer. Found in one of the questions Mokubai linked. – user1785730 Mar 13 '21 at 20:24

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