FMDF fmdefrancesco at gmail.com
Thu Sep 23 03:22:24 EDT 2021

On Thu, 23 Sep 2021, 09:11 FMDF, <fmdefrancesco at gmail.com> wrote:

> On Wed, 22 Sep 2021, 08:22 Ruben Safir, <ruben at mrbrklyn.com> wrote:
>> What is this for?
>> efivarfs on /sys/firmware/efi/efivars type efivarfs
>> why would the OS need to know anything about the UEFI
>> boot loader once it is up and running?
> I think you are still making confusion: UEFI bootloaders and UEFI are two
> different entities.
> UEFI bootloaders (like Grub2) serve the purpose to locate, pass kernel
> options  and platform information to the kernel that themselves are going
> to boot.
> Instead the UEFI is an interface between the running OS and the platform
> firmware.
> UEFI defines two types of services: boot services and runtime services.
> After booting is done, via UEFI boot services and eventually UEFI
> bootloaders, the OS does not need anymore the bootloader and the UEFI boot
> services.
> Instead the OS needs UEFI runtime services to talk to the platform
> firmware. For example, if OS cannot talk to the platform via UEFI, it
> cannot even shutdown the system (obviously there is much more than simply
> shutting down). How can an OS know that you've attached a plug and play
> device if it cannot talk to the platform firmware?
> Fabio

For sake of completeness and for better understanding that OS need UEFI,
but not necessarily EFI bootloaders, please read the following document:


Linux can boot without bootloaders, but it still needs to use UEFI at


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