Question When and how to set up a sufficiently large EFI partition for dual Secure Boot?

Mar 29, 2021
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Let's assume you wish to install Debian stable „bullseye“ amd64 and Windows 11 for dual boot with Secure Boot on a modern computer. Lower bounds on the size of a EFI partition have been suggested. How do you best create this EFI partition:
  • before installing both operating systems and hoping that both will use it as it is,
  • during Debian installation and hoping that Windows 11 will use it, or
  • during Windows installation and hoping that Debian bullseye will use it?
In particular, you wish to avoid having two EFI partitions, and you wish to avoid resizing or moving an already created EFI partition afterwards.
So which actions exactly do you perform and in which order?
 

Ralston18

Titan
Moderator
Your question appears to be a homework question.

Forum rules prohibit doing or assistance with homework.

Even though the question may not be homework there is no way to for us to know the truth of the matter.

Instead, present your questions along with what you believe are the answers and include your supporting information.

Then request assistance and comment.
 
Best way is to create the uefi partition on a clean disk, if it is the first partition on the boot disk then the system will always boot from that, Windows will pick up on it and automatically add itself to the boot menu, for linux I'm not sure, it does ask you at some point where you want to install the boot loader, if you don't let linux install any bootloader you can add the linux OS to the boot menu by using either the recovery console of windows if you want to do it manually or by using easybcd from windows.

You also don't need a boot partition, windows can have the boot files on the same partition as windows, then you only need to create a partition for linux, don't let it install bootloader and add it with easybcd.

I'm sure you can do the same thing with grub or whatever linux uses for uefi, I'm just not familiar with that side of things.
 
Mar 29, 2021
101
18
85
0
Your question appears to be a homework question.

Forum rules prohibit doing or assistance with homework.

Even though the question may not be homework there is no way to for us to know the truth of the matter.

Instead, present your questions along with what you believe are the answers and include your supporting information.

Then request assistance and comment.
Are you serious? Homework for which course at which institution? For the course on operating systems (at least 2-3 courses that I am aware of) such a question would have been considered too technical, too low-level and probably undoable unless the teacher went for the extremely specific topic of dual booting. I know nobody who actually teaches dual booting, though folks sometimes teach virtual machines.
Anyway, I don't know the answers; asking questions is exactly what we do to get them. By definition.
 
Mar 29, 2021
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Best way is to create the uefi partition on a clean disk, if it is the first partition on the boot disk then the system will always boot from that, Windows will pick up on it and automatically add itself to the boot menu, for linux I'm not sure, it does ask you at some point where you want to install the boot loader, if you don't let linux install any bootloader you can add the linux OS to the boot menu by using either the recovery console of windows if you want to do it manually or by using easybcd from windows.

You also don't need a boot partition, windows can have the boot files on the same partition as windows, then you only need to create a partition for linux, don't let it install bootloader and add it with easybcd.

I'm sure you can do the same thing with grub or whatever linux uses for uefi, I'm just not familiar with that side of things.
Hm, not sure I understand you, but thanks anyway. When you speak about the boot menu, do you mean the boot menu produced by BIOS UEFI or the boot menu produced by the bootloader stored in the EFI system partition?
 
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Hm, not sure I understand you, but thanks anyway. When you speak about the boot menu, do you mean the boot menu produced by BIOS UEFI or the boot menu produced by the bootloader stored in the EFI system partition?
I am talking about the bcdstore (boot configuration data) that windows uses to boot into the OS, you can use that to add linux, iso images, os images on .vhd, floppies, anything that is bootable can be added to it.
 

Ralston18

Titan
Moderator
Yes. I am serious. Again there is no way to really know the situation.

There are all sorts of institutions and classes all over the world and we regularly see questions such as you asked.

And other questions at all different levels.

Fully agree that it is important to ask questions.

However, in many environments, it will serve you well to ask a question but also provide and support what you believe to be the answer. Or at provide some underlying work to show a good faith effort to find the answer.

For example, if I am following in all correctly then (per @TerryLaze ) then following links may prove helpful.

https://docs.microsoft.com/en-us/previous-versions/windows/desktop/bcd/bcdstore

or maybe

https://www.lifewire.com/how-to-rebuild-the-bcd-in-windows-2624508

[Note if I am off track the error is mine not @TerryLaze .]

Show us what you are working on, what you have done (or attempted to do), the results thereof, and what you believe to be the problem and/or answer.

By definition: "Teach a person to fish....."
 
Why do you assume that my drive has any partition at all, in fact, any data at all in its current state?
Why do you assume that I assume that?
You asked about efi partitions so we talk about efi partitions, nobdy said that you have anything on your drive.
The EFI partition is one of two things, either a windows system partition or a generic efi system partition both of these two are doing the same thing, they hold the files needed to boot the different OS on the disk.
If you ask random people 99 out of 100 will tell you about windows system partition and bcd.
 
Mar 29, 2021
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Why do you assume that I assume that?
I don't understand you I'm afraid. You wrote: “the boot partition that has the bcd store of windows.” This boot partition you mentioned (the one with the BCD store of Windows) resides on the drive in your opinion, right? I.e., on the SSD or HDD of your computer (assuming there is just one storage), right? Or does it reside is some other nonvolatile memory, say, on the motherboard?
 
I don't understand you I'm afraid. You wrote: “the boot partition that has the bcd store of windows.” This boot partition you mentioned (the one with the BCD store of Windows) resides on the drive in your opinion, right? I.e., on the SSD or HDD of your computer (assuming there is just one storage), right? Or does it reside is some other nonvolatile memory, say, on the motherboard?
Yes, but I'm not saying that it exists on your harddrive, I'm saying in general that that is the efi partition of windows and that that is what almost all people understand under efi partition.
 

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