I need autoinstall guidance for Windows 11 Pro

Question

I have a semi-working autounattend.xml file. It's only semi because there is a hiccup.

Computer configuration:

1 500 GB SSD (For Linux Debian 12)

1 4 TB HD (For Windows 11 Pro)

I have 2 autoinstall isos, one for Debian and one for Windows and I have them on one bootable Drive. I start the computer and choose to boot from the UEFI USB because if I choose the non-UEFI option it won't get past the selection screen. At the time I'm doing this, both drives are clean with no partitions. If I install Debian first, it autoinstalls on sda and everything goes fine. I can boot into it afterwards and everything works. I then go to install Windows because I've heard that Windows will try to control how things boot so I figured it would be simpler to just install it last.

Scenario 1

When I try to install on sdb (configured within the autounattend.xml) I get an error that partition 4 can't be created but after leaving the installer and looking at that drive I see that it was properly partitioned.

<DiskConfiguration>

<Disk wcm:action="add">

<DiskID>1</DiskID>

<WillWipeDisk>true</WillWipeDisk>

<CreatePartitions>

<!-- Windows RE Tools partition -->

<CreatePartition wcm:action="add">

<Order>1</Order>

<Type>Primary</Type>

<Size>300</Size>

</CreatePartition>

<!-- System partition (ESP) -->

<CreatePartition wcm:action="add">

<Order>2</Order>

<Type>EFI</Type>

<Size>100</Size>

</CreatePartition>

<!-- Microsoft reserved partition (MSR) -->

<CreatePartition wcm:action="add">

<Order>3</Order>

<Type>MSR</Type>

<Size>128</Size>

</CreatePartition>

<!-- Windows partition -->

<CreatePartition wcm:action="add">

<Order>4</Order>

<Type>Primary</Type>

<Extend>true</Extend>

</CreatePartition>

</CreatePartitions>

<ModifyPartitions>

<!-- Windows RE Tools partition -->

<ModifyPartition wcm:action="add">

<Order>1</Order>

<PartitionID>1</PartitionID>

<Label>WINRE</Label>

<Format>NTFS</Format>

<TypeID>C</TypeID>

</ModifyPartition>

<!-- System partition (ESP) -->

<ModifyPartition wcm:action="add">

<Order>2</Order>

<PartitionID>2</PartitionID>

<Label>System</Label>

<Format>FAT32</Format>

</ModifyPartition>

<!-- MSR partition does not need to be modified -->

<ModifyPartition wcm:action="add">

<Order>3</Order>

<PartitionID>3</PartitionID>

</ModifyPartition>

<!-- Windows partition -->

<ModifyPartition wcm:action="add">

<Order>4</Order>

<PartitionID>4</PartitionID>

<Label>OS</Label>

<Letter>C</Letter>

<Format>NTFS</Format>

</ModifyPartition>

</ModifyPartitions>

</Disk>

</DiskConfiguration>

I have to do a manual install to complete the installation. If I were to then do an autoinstall on top of that install, the install completes just fine using the same partition scheme. If I set it to install on sda, everything is fine.

Answer 1

The Windows bootloader will override any Linux bootloaders (e.g. GRUB).

So I suggest you install Windows first and then Linux as the GRUB bootloader should detect Windows and add it correctly.

Also Windows Update or Upgrades may restore the original Windows bootloader again (e.g. override GRUB).