[SOLVED] Booting the windows 11 installer ISO from GRUB

[summer heath]

I would like to add the windows 11 installer ISO to the grub boot menu on a portable NVME drive to use a multi-tool USB of sorts. (yes I know ventoy exists but it's unclear how to use it as a bootloader and I would like to get grub working since I know it's possible)

I have spent the last two days trying and this is what I've figured out:

1. I should boot GRUB in BIOS mode not UEFI mode to support the linux16 & initrd16 commands needed to load wimboot (currently not supported on mainline grub and I couldn't find any maintained forks). The NVME drive is less then 2TB so this works fine.

2. It's unclear if wimboot supports booting directly from the unmodified Win11_24H2_EnglishInternational_x64.iso so files may need to be provided + newc:<stuff> may need to be added in the grub boot option.

3. This my current boot script (see attached video for what happens when I try boot it)

menuentry "Windows 11 Install (BIOS)" {
    insmod part_gpt
    insmod fat
    insmod udf
    set isofile="/iso/Win11_24H2_EnglishInternational_x64.iso"
    loopback loop $isofile
    linux16 /wimboot/wimboot
    initrd16 \
    newc:bootmgr.exe:/wimboot/bootmgr.exe \
        newc:null.cfg:/wimboot/null.cfg \
        newc:winpeshl.ini:/wimboot/winpeshl.ini \
    newc:startup.bat.sdi:/wimboot/startup.bat \
        newc:boot.sdi:(loop)/boot/boot.sdi \
    newc:bcd:(loop)/boot/bcd \
        newc:boot.wim:(loop)/sources/boot.wim
    boot
}

4. I have also managed to get into the "windows boot manager" once with the error 0xc000000f, I cannot seem to reproduce this.
5. I have been testing with mainly with qemu but do test on bare metal too.
6. grub->iPXE is technically an option but I don't think I want to do that because it requires putting files on the efi partition (which I want to keep small).

I am very lost so any help or insight would be appreciated. I've attached some auxiliary scripts and stuff that is references in the grub boot entry (that I store under /etc/grub.d/40_custom)

[lapis bone]

this ca be achevieved with ventoy

[summer heath]

I had a brief look online and I can't seem to find any information on using ventoy to host a non immutable full operating system

[lapis bone]

from my understanding you want to boot windows iso to install it, right?

[summer heath]

Kinda, I want to create a drive that 1: has a full arch operating system for me to use, 2. utilities like the windows installer I need to install windows on a machine

[lapis bone]

then in that case, just add your iso to grub

grub can boot isos, it's what ventoy uses to work

that way you have arch on an external drive, yet you can boot iso files

I recall some guides telling how to

[summer heath]

This is what the post is about, it's not that simple please read above. ventoy uses an inhouse grub fork to allow booting wimboot to boot windows isos

[lapis bone]

it's also not overcomplicated. but at least I understand what you want to do. due to timezones, you may wait some time until other more skilled users can lend you a hand

[summer heath]

most guides are tailored towards linux ISOs which is a completely different process to getting the windows 11 installer to run. I have added other linux ISOs to grub before.

As for guides I found these two links:
https://rmprepusb.com/tutorials/145-install-windows-directly-from-an-iso-file-using-ipxe-wimboot-mbruefi-grub2grub4dos/
https://github.com/Thermionix/thermionix.github.com/blob/master/_posts/2014-08-14-grub2-wimboot-winpe.md
I have gotten as far as I have from those

[lapis bone]

yes, sorry for misreading your thread, kinda tired. but rest assured others may come to help.

[cloud fulcrum]

https://www.ventoy.net/en/doc_disk_layout.html#reserve_space

Ventoy + reserved space and then install linux in to that?

@summer heath

[summer heath]

How would one boot into linux from ventoy using that?

[cloud fulcrum]

Maybe copy the efi file grub makes with --removable on to the ventoy partition?

Maybe some configuration can be manually added in to the ventoy grub

I'm checking

@summer heath https://www.ventoy.net/en/plugin_grubmenu.html

Generate the grub config with grub-mkconfig, then copy the entries you want

[summer heath]

Ok thank you I'll check that out. You've been a lifesaver.

[native juniper]

hm7 received a thank you cookie!

[cloud fulcrum]

If you're not booted in to the system then mounting the linux partition on the ventoy usb could make mkconfig detect linux

if not then enable os-prober

[summer heath]

I should be able to figure it out, worst case I can manually add the entries

[summer heath]

I took the menu entries from grub-mkconfig and added it /ventoy/ventoy_grub.cfg and it seems to work (need to press f6 to bring it up but that's fine)

Once again thanks

[cloud fulcrum]

You're welcome

... solved

[cerulean narwhal]

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Thank you

[summer heath]

[Solved] Booting the windows 11 installer ISO from GRUB