Introduction

I’ve recently tried UTM on my Apple Silicon MBP to test Windows 11. To install Windows 11, I needed a recent iso image. This blog post explains how to download the iso files for Windows 10 or 11.

Get Windows 11 Insider Preview

Go to UUP dump. This page lists all available UUP files from Windows Update servers.

Search for “feature update Windows 10” or “Windows 11 Insider Preview” and select a recent version for the required architecture (e.g. x64). Click on next.

Select a language and click next.

Select an edition, like “Windows Pro” and click next.

Select Download method “Download and convert to ISO”. Check “Include updates” and click on “Create download package”.

Extract the resulting file. You’ll see three scripts:

Windows: uup_download_windows.cmd
Linux: uup_download_linux.sh
macOS: uup_download_macos.sh

Make the uup_download_macos.sh executable by using “chmod +x uup_download_macos.sh” and try to execute it.

It will probably complain about missing files. But at the same time, it offers help on what you’ll need to install using homebrew, e.g.:

brew tap sidneys/homebrew
brew install aria2 cabextract wimlib cdrtools sidneys/homebrew/chntpw

Fix for Apple Silicon Macs

On my M1/Apple Silicon Mac, chntpw complained about a non working SSL. I’ve found this issue on Github, which has some easy installation recommendations:

curl -LO https://gist.github.com/minacle/e9dedb8c17025a23a453f8f30eced3da/raw/908b944b3fe2e9f348fbe8b8800daebd87b5966c/openssl@1.0.rb
curl -LO https://gist.github.com/minacle/e9dedb8c17025a23a453f8f30eced3da/raw/908b944b3fe2e9f348fbe8b8800daebd87b5966c/chntpw.rb
brew install --formula --build-from-source ./openssl@1.0.rb
brew install --formula --build-from-source ./chntpw.rb
rm ./openssl@1.0.rb ./chntpw.rb

Now try to execute the uup_download_macos.sh script again. It will now download the requested update files and will create automatically a nice ISO file, which can be used to install Windows.

Legal disclaimers

As we’re using the official Windows Server Update files, this method should be legal. There is a more detailed report available at win10.guru which explains, that most of the tool was developed by analyzing the network traffic of a Windows installation running updates. It’s also a good way to get the versions including the latest updates including the Insider builds. Of course there’s still the official download page from Microsoft.