How can I create a larger EFI partition during a fresh Windows 11 Pro install

StonyCreeker · Wednesday at 3:53 PM

When we receive new systems, we install a custom image over the preinstalled Windows. Unfortunately, our custom images are based on downloads from the VLSC (or whatever its replacement is called). This causes the standard 100 MB EFI partition to be created during installation. The OEM EFI partition is/was 260 MB and some of their BIOS updates require the larger EFI partition (or at least that's what their support told me when I couldn't get a BIOS install to work).

I know I can change the size of the EFI partition after installation using third party software but I'm wondering if there is a way to get Windows to create a larger partition during installation so I don't need to use third party tools.

Any ideas?

garlin · Wednesday at 4:27 PM

Regardless of which Windows image you use to install, you can define a custom disk layout in autounattend.xml.

There are two methods:
1. Use the old-style <DiskConfiguration> method, but this has a drawback of you can't place WinRE as the last partition as per current MS guidance on imaging.

2. Use diskpart commands in WinPE pass to create the disk layout. Because you're allowed to shrink partitions, you can carve out the last partition for WinRE and still allow Windows to take the remaining space.

Code:

<?xml version="1.0" encoding="utf-8"?>
<unattend xmlns="urn:schemas-microsoft-com:unattend">
    <settings pass="windowsPE">
        <component name="Microsoft-Windows-Setup" processorArchitecture="amd64" publicKeyToken="31bf3856ad364e35" language="neutral" versionScope="nonSxS" xmlns:wcm="http://schemas.microsoft.com/WMIConfig/2002/State" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
            <ImageInstall>
                <OSImage>
                    <InstallTo>
                        <DiskID>0</DiskID>
                        <PartitionID>3</PartitionID>
                    </InstallTo>
                </OSImage>
            </ImageInstall>
            <RunSynchronous>
                <RunSynchronousCommand wcm:action="add">
                    <Order>1</Order>
                    <Path>cmd /c (for %a in ("sel dis 0" "cle" "con gpt" "cre par efi size=260" "for quick fs=fat32" "cre par msr size=16" "cre par pri" "shr minimum=800" "for quick fs=ntfs") do @echo %~a) &gt; X:\UEFI.txt</Path>
                </RunSynchronousCommand>
                <RunSynchronousCommand wcm:action="add">
                    <Order>2</Order>
                    <Path>cmd /c (for %a in ("cre par pri" "for quick fs=ntfs" "set id=de94bba4-06d1-4d40-a16a-bfd50179d6ac" "gpt attributes=0x8000000000000001") do @echo %~a) &gt;&gt; X:\UEFI.txt &amp; diskpart /s X:\UEFI.txt</Path>
                </RunSynchronousCommand>
            </RunSynchronous>
            <UserData>
                <ProductKey>
                    <Key></Key>
                </ProductKey>
            </UserData>
        </component>
    </settings>
</unattend>

Equivalent to running diskpart with:

Code:

select disk 0
clean
convert gpt
create partition efi size=260
format quick fs=fat32
create partition msr size=16
create partition primary
shrink minimum=800
format quick fs=ntfs
create partition primary
format quick fs=ntfs
set id=de94bba4-06d1-4d40-a16a-bfd50179d6ac
gpt attributes=0x8000000000000001

Megahertz · Wednesday at 5:45 PM

StonyCreeker said:
When we receive new systems, we install a custom image over the preinstalled Windows. Unfortunately, our custom images are based on downloads from the VLSC (or whatever its replacement is called). This causes the standard 100 MB EFI partition to be created during installation. The OEM EFI partition is/was 260 MB and some of their BIOS updates require the larger EFI partition (or at least that's what their support told me when I couldn't get a BIOS install to work).

I know I can change the size of the EFI partition after installation using third party software but I'm wondering if there is a way to get Windows to create a larger partition during installation so I don't need to use third party tools.

Any ideas?

It doesn't make sense. I have a dual boot and my 100M EFI partition still has 70M free.
Even if it requires a Win OS environment to update BIOS, this should be done in Win RE (recovery). The EFI partition should only point to a boot able partition, not hold app or OS, so I don't know why you need a big EFI partition.

Anyway, one solution to have a big EFI as a template is to install the VLSC till the first boot. All partition will be created. Don't let it reboot. Shut down.
Install the drive on a computer with Win 10 or Win 11.
With a good disk manager like Minitool or DiskGenius enlarge the EFI partition.
Create a drive image with Macrium or another good image / clone software.
Apply the image on drives of the computers you want to have the VLSC.

When you boot the computer with the applied image it will restart the installation process (create user profile etc) but the EFI partition will be the size you set on the template drive.

garlin · Wednesday at 6:41 PM

When running Dell or HP management tools, it's possible to run out of EFI space because they hide firmware backups and other stuff there. Some OSD admins will encourage those users to assign even more space than 260 MB.

For a home user, 100 MB is typically enough.
For the enterprise, the current guideline is 260 MB.

Megahertz · Wednesday at 7:30 PM

garlin said:
When running Dell or HP management tools, it's possible to run out of EFI space because they hide firmware backups and other stuff there. Some OSD admins will encourage those users to assign even more space than 260 MB.

For a home user, 100 MB is typically enough.
For the enterprise, the current guideline is 260 MB.

Thanks for the explanation. I never had a new Dell or HP computer as I assemble my own computers.
I think I saw a Tools partition on a Dell or HP with the management tools on it.

hsehestedt · Wednesday at 8:03 PM

FYI, here is the technical reason for the 260 MB EFI partition...

Normally 100 MB is just fine, however, the EFI partition is formatted as FAT32 and on advanced format native 4k drives the minimum partition size for FAT32 is - you guessed correctly - 260 MB. So, by using a 260 MB EFI partition you guarantee compatibility with ALL systems.

In fact, in all my unattended answer files that partition the drive, I use 260 MB for my EFI partition just to guarantee compatibility with any system that I might encounter.

hsehestedt · Wednesday at 8:17 PM

garlin said:
you can define a custom disk layout in autounattend.xml.

When I started to read this post my attention was immediately drawn to the lines you used to do the partitioning. That looks so much cleaner than what I have been doing which looks like this:

XML:

            <RunSynchronous>
                <RunSynchronousCommand wcm:action="add">
                    <Order>1</Order>
                    <Path>reg add HKLM\System\Setup\LabConfig /v BypassTPMCheck /t reg_dword /d 0x00000001 /f</Path>
                </RunSynchronousCommand>
                <RunSynchronousCommand wcm:action="add">
                    <Order>2</Order>
                    <Path>reg add HKLM\System\Setup\LabConfig /v BypassSecureBootCheck /t reg_dword /d 0x00000001 /f</Path>
                </RunSynchronousCommand>
                <RunSynchronousCommand wcm:action="add">
                    <Order>3</Order>
                    <Path>reg add HKLM\System\Setup\LabConfig /v BypassRAMCheck /t reg_dword /d 0x00000001 /f</Path>
                </RunSynchronousCommand>
                <RunSynchronousCommand wcm:action="add">
                    <Order>4</Order>
                    <Path>cmd.exe /c echo select disk 0 &gt;&gt; X:\diskpartUEFI.txt</Path>
                </RunSynchronousCommand>
                <RunSynchronousCommand wcm:action="add">
                    <Order>5</Order>
                    <Path>cmd.exe /c echo clean &gt;&gt; X:\diskpartUEFI.txt</Path>
                </RunSynchronousCommand>
                <RunSynchronousCommand wcm:action="add">
                    <Order>6</Order>
                    <Path>cmd.exe /c echo convert gpt &gt;&gt; X:\diskpartUEFI.txt</Path>
                </RunSynchronousCommand>
                <RunSynchronousCommand wcm:action="add">
                    <Order>7</Order>
                    <Path>cmd.exe /c echo create partition efi size=260 &gt;&gt; X:\diskpartUEFI.txt</Path>
                </RunSynchronousCommand>
                <RunSynchronousCommand wcm:action="add">
                    <Order>8</Order>
                    <Path>cmd.exe /c echo format fs=fat32 quick label=&quot;System&quot; &gt;&gt; X:\diskpartUEFI.txt</Path>
                </RunSynchronousCommand>
                <RunSynchronousCommand wcm:action="add">
                    <Order>9</Order>
                    <Path>cmd.exe /c echo create partition msr size=128 &gt;&gt; X:\diskpartUEFI.txt</Path>
                </RunSynchronousCommand>
                <RunSynchronousCommand wcm:action="add">
                    <Order>10</Order>
                    <Path>cmd.exe /c echo create partition primary &gt;&gt; X:\diskpartUEFI.txt</Path>
                </RunSynchronousCommand>
                <RunSynchronousCommand wcm:action="add">
                    <Order>11</Order>
                    <Path>cmd.exe /c echo shrink desired=2048 minimum=2048  &gt;&gt; X:\diskpartUEFI.txt</Path>
                </RunSynchronousCommand>
                <RunSynchronousCommand wcm:action="add">
                    <Order>12</Order>
                    <Path>cmd.exe /c echo format fs=ntfs quick label=&quot;Windows&quot; &gt;&gt; X:\diskpartUEFI.txt</Path>
                </RunSynchronousCommand>
                <RunSynchronousCommand wcm:action="add">
                    <Order>13</Order>
                    <Path>cmd.exe /c echo assign letter=W &gt;&gt; X:\diskpartUEFI.txt</Path>
                </RunSynchronousCommand>
                <RunSynchronousCommand wcm:action="add">
                    <Order>14</Order>
                    <Path>cmd.exe /c echo create partition primary &gt;&gt; X:\diskpartUEFI.txt</Path>
                </RunSynchronousCommand>
                <RunSynchronousCommand wcm:action="add">
                    <Order>15</Order>
                    <Path>cmd.exe /c echo format fs=ntfs quick label=&quot;Recovery&quot; &gt;&gt; X:\diskpartUEFI.txt</Path>
                </RunSynchronousCommand>
                <RunSynchronousCommand wcm:action="add">
                    <Order>16</Order>
                    <Path>cmd.exe /c echo set id=&quot;de94bba4-06d1-4d40-a16a-bfd50179d6ac&quot; &gt;&gt; X:\diskpartUEFI.txt</Path>
                </RunSynchronousCommand>
                <RunSynchronousCommand wcm:action="add">
                    <Order>17</Order>
                    <Path>cmd.exe /c echo gpt attributes=0x8000000000000001 &gt;&gt; X:\diskpartUEFI.txt</Path>
                </RunSynchronousCommand>
                <RunSynchronousCommand wcm:action="add">
                    <Order>18</Order>
                    <Path>cmd.exe /c echo exit &gt;&gt; X:\diskpartUEFI.txt</Path>
                </RunSynchronousCommand>
                <RunSynchronousCommand wcm:action="add">
                    <Order>19</Order>
                    <Path>cmd.exe /c diskpart.exe /s X:\DiskPartUEFI.txt</Path>
                </RunSynchronousCommand>
            </RunSynchronous>

Thanks again for sharing. Just love reading your posts

and cannot wait to try this out.

My stuff works, and it works well, but I love when I discover better ways to do things.

garlin · Wednesday at 8:35 PM

One day it occurred to me that diskpart accepts abbreviations for most commands. So I had to figure out the shortest one for each line.
"exit" is never required as the last line when calling diskpart /s or from a pipe.

This script took me two weeks to squeeze out all the unnecessary characters. Unfortunately, VBScript is going away.

Code:

<RunSynchronousCommand wcm:action="add">
    <Order>1</Order>
    <Path>cmd /c echo A=Split(WScript.Arguments(0),","): For i=0 to UBound(A): B=B ^&amp; """" ^&amp; A(i) ^&amp; """ ": Next: C="cmd /c (for %a in (" ^&amp; B ^&amp; ") do @echo %~a) | diskpart": CreateObject("WScript.Shell").Run C,0,True &gt; HIDE.vbs</Path>
</RunSynchronousCommand>
<RunSynchronousCommand wcm:action="add">
    <Order>2</Order>
    <Path>wscript HIDE.vbs "sel dis 0,cle,con gpt,cre par efi size=100,for quick fs=fat32,cre par msr size=16,cre par pri,shr minimum=800,for quick fs=ntfs,cre par pri,for quick fs=ntfs,set id=de94bba4-06d1-4d40-a16a-bfd50179d6ac,gpt attributes=0x8000000000000001"</Path>
</RunSynchronousCommand>

StonyCreeker · Thursday at 2:45 PM

Wow! Such quick and informative replies. Thank you!

Unfortunately, I'm quite new to imaging and have never used, let alone created, an autounattended.xml. Does anyone have any suggestions of where I can quickly learn enough basics to implement the diskpart version in gerlin's reply, then subsequently teach myself the topic more fully? A quick search brought me to several Microsoft Learn pages, but much of it assumes knowledge I do not yet have.

I did find an ElevenForum post about a generator for creating autounattended.xml files. I hope it's sufficient to get me started immediately.

autounattend.xml generator

The generator has a section for specifying the size of the EFI partition. Does anyone have any experience using this or know of another generator that they prefer?
If you have used this, can you tell me if the default settings yield the same result as doing the install without an autounattended.xml? If not, are any of the changes "significant"?

I'll be giving it a try while I wait for any suggestions.

Thanks again

garlin · Thursday at 3:01 PM

There's a number of unattended file generators.
All you need to know (for now), is do you agree with this recommended disk layout?

Code:

select disk 0
clean
convert gpt    ==> GPT mode (not MBR)
create partition efi size=260    ==> System (EFI) = 260 MB (recommended minimum)
format quick fs=fat32
create partition msr size=16    ==> MSR = 16 MB (default)
create partition primary
shrink minimum=800   ==> take remaining space for Windows, but return 800MB for Recovery (consensus recommendation)
format quick fs=ntfs
create partition primary
format quick fs=ntfs
set id=de94bba4-06d1-4d40-a16a-bfd50179d6ac
gpt attributes=0x8000000000000001

Schneegan's site has a web box where you can copy the provided diskpart commands, and it'll crank it out (but in a less compact form).

Using this layout, EFI + MSR + Recovery will be fixed in size, but Windows will be whatever is left after subtracting the other 3 partitions. If you don't provide an unattended file, Setup will reuse any pre-existing partitions it finds, or create a new layout using default sizes for EFI and Recovery (which might be too small for your needs).

With an unattended file, you will always get what you want (if correctly laid out).

hsehestedt · Thursday at 3:37 PM

If you prefer to do this without an unattended install, and simply do a normal installation, you can do so like this without needing any special knowledge:

1) Copy the text in the box below to a text file. You can name that file anything you want, I use the name Partitioning.txt in my example below. This text file will serve as a script for diskpart to automatically partition the drive.

Code:

REM Last Updated on July 3, 2025

REM This script is intended for modern UEFI systems, not systems with Legacy BIOS.

REM Remove all partitions from disk 0 by performing a CLEAN, then initialize
REM the drive as GPT.

select disk 0
clean
convert gpt

REM Create an EFI partition. Note, the EFI partition only needs to be 100 MB
REM in size, but I always use 260 MB because on an advanced 4k format drive
REM the minimum size for a FAT32 partition is 260 MB. By using 260 MB we
REM guarantee this to work on all drives.

create partition efi size=260
format fs=fat32 quick

REM Create an MSR partition. Note that MSR partitions are not formatted.

create partition msr size=128

REM Create a partition for Windows using all remaining space on the disk.
REM After creating it, shrink it by 2 GB. This will give us 2 GB of free
REM space to create a Recovery Tools partition. Note that 2GB is larger
REM than the typical size. Try changing the "2048" below to "1024" if
REM you would prefer a 1GB option to save space.

create partition primary
shrink desired=2048
format fs=ntfs quick label="Windows"

REM Create the Recovery Tools partition. We don't specify a size because we
REM will allow it to occupy all remaining space on the drive (2 GB obtained
REM from shrinking the Windows partition using the "shrink" command above).

create partition primary
set id="de94bba4-06d1-4d40-a16a-bfd50179d6ac"
gpt attributes=0x8000000000000001
format fs=ntfs quick

2) Drop this file onto the root of your Windows installation media. If you use a dual partition installation media (a small FAT32 partition and a larger NTFS partition) you can drop the file onto either partition.

3) Start you Windows installation as usual by booting from the installation media.

4) When you reach the first static screen, press SHIFT + F10 to open a command prompt.

5) Now you need to figure out what drive letter your Windows install media has. From the command prompt, issue these 2 commands:

C:
dir

If you get an error after typing C: and pressing ENTER, move on to D:, then E:, etc. Likewise, if you run the dir command and do not see the file Partitioning.txt, then move on to the next drive letter. You want to repeat until you find the drive letter where you see the file named Partitioning.txt after you issue the dir command.

Once you find the correct drive letter, make a note of it.

6) You notice that in the script I reference disk 0. The disk to which you want to install Windows in NOT always disk 0! We want to determine the correct disk ID because running the script will wipe out and repartition the drive we specify, and you do not want to erase the wrong drive!

From that command prompt, run diskpart. Once diskpart has started run the command list disk. Hopefully, from the size, you can determine which disk you wish to install Windows on.

NOTE: If that is not enough to identify the correct disk, let me know. There are additional steps we can take.

Take note of the disk ID. If it is anything other than disk 0, reboot into Windows and change that disk number in the partitioning.txt file, then boot from your install media again and continue with step 7.

7) Exit from diskpart by issuing the command exit. That will drop you back to a standard command prompt.

8) Run these commands:

NOTE: In the below command, replace E: with the drive letter you determined earlier to be where Partitioning.txt is located.

diskpart /S E:\Partitioning.txt
exit

The drive specified in the script will be wiped and partitioned and the command prompt will be closed after you run exit.

9) Simply continue Windows installation as always now. When asked where to install Windows choose the partition that is labeled "Windows". Continue installation to completion.

I hope that this helps! If you have any questions, you know where to find me

Megahertz · Thursday at 7:52 PM

hsehestedt said:
5) Now you need to figure out what drive letter your Windows install media has. From the command prompt, issue these 2 commands:

C:
dir

Why not use diskpart >list vol to identify the installation volume?

Megahertz · Thursday at 7:56 PM

StonyCreeker said:
When we receive new systems, we install a custom image over the preinstalled Windows. Unfortunately, our custom images are based on downloads from the VLSC (or whatever its replacement is called). This causes the standard 100 MB EFI partition to be created during installation. The OEM EFI partition is/was 260 MB and some of their BIOS updates require the larger EFI partition (or at least that's what their support told me when I couldn't get a BIOS install to work).

I know I can change the size of the EFI partition after installation using third party software but I'm wondering if there is a way to get Windows to create a larger partition during installation so I don't need to use third party tools.

Any ideas?

Why not format the original Win partition and apply the Win VLSC image on the partition. This will keep the original EFI and the Tools partition that has the diagnostic and maintenance tools.

hsehestedt · Thursday at 7:58 PM

Megahertz said:
Why not use diskpart >list vol to identify the installation volume?

Because list vol does not give you the disk ID that we are after.

Megahertz · Thursday at 9:39 PM

hsehestedt said:
Because list vol does not give you the disk ID that we are after.

And dir does?

Megahertz · Thursday at 10:31 PM

I still think that creating a template drive and then applying the image to the other computers is the best solution.
On Audit mode you can install many applications, like MS Office, and some customization. When on the computer, it will continue installation and it will start at OOBE (create the user profile) so the installation is on last phase so it is very fast.

hsehestedt · Thursday at 11:12 PM

Megahertz said:
And dir does?

No - list disk does that.

The first words in my earlier post were "If you prefer to do this without an unattended install, and simply do a normal installation"...

This is because it was noted that some other methods like unattended setup would have a learning curve. I was trying to provide a very simple method that requires no specialized knowledge.

Megahertz · Thursday at 11:25 PM

hsehestedt said:
No - list disk does that.

The first words in my earlier post were "If you prefer to do this without an unattended install, and simply do a normal installation"...

This is because it was noted that some other methods like unattended setup would have a learning curve. I was trying to provide a very simple method that requires no specialized knowledge.

I understood all your code.
I only thought that instead trying dir c:, dir D: etc a list vol would list all volume so you could identify the one that has the diskpart script

hsehestedt · 2025-07-04T00:24:49-0400

Megahertz said:
I understood all your code.
I only thought that instead trying dir c:, dir D: etc a list vol would list all volume so you could identify the one that has the diskpart script

Ok, now I understand. Yeah, that might tell you but some people might not no for sure what to look for. Ultimately, issuing a DIR will tell you for sure, but your method may do well also.

zbook · 2025-07-04T04:35:36-0400

What is to be installed within the EFI partition?

Which error messages / codes were seen during attempted upgrades?

Please update the website "My Computers" section.

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