Testing CimFS (Composite File System) – Windows Virtual Desktop


On the 15th of October 2020, I was kindly invited to be interviewed and present on the WVD Community Podcast. For all those who watched, you will note that I spoke about MSIX App Attach and the proposed new file system CimFS. If you missed it, you can find it here.

As I discussed and announced on the podcast, the tool I wrote for mounting and unmounting CimFS files, this is now freely available to the community for testing.

This tool allows the community to carry out performance tests, provide feedback and get a basic understanding of CimFS in preparation for further Microsoft announcements. Feedback is welcome…

Announcements on the podcast:

AppCURE – The preview version released on the 16th of October, enables you to create Cim images ready for the potential release of the WVD MSIX portal preview/GA in November 2020. If you want to start packaging .cim images. get in touch https://www.appcure.io

CIMUTIL – The Community tool allows you to mount and dismount pre-packages .cim files including pinball, putty and notepad++. This is freely available to the community for personal use. To use the tool, you need to register for a community key here:


You can download the (.cim) files and the cimutil here: https://github.com/RMITBLOG/MSIX_APP_ATTACH

WVD Quickstart ebook – The recently published eBook by Microsoft “Quickstart guide to Windows Virtual Desktop” can be found here: https://azure.microsoft.com/en-us/resources/quickstart-guide-to-windows-virtual-desktop/

A Introduction to MSIX App Attach book – available to pre-order now on Amazon: https://www.amazon.co.uk/Introduction-MSIX-App-Attach-Windows-ebook/dp/B08L43M6KM/ref=sr_1_1?dchild=1&keywords=ryan+mangan&qid=1602843238&sr=8-1

I also announced the community page for the book where I will provide a resources page for the community for those who have created MSIX App Attach posts. If you would like to be included, you just need to message me with your details.

Getting Started with CimFS

Step one: you need to ensure the VM or WVD Session host, or desktop is on Build 2004.

Setup two: Install the CimUtil application. You will need to request a licence key from: https://ryanmangansitblog.com/cimutil-key-registration/

Step three: Download the Cim Application zip from GitHub (https://github.com/RMITBLOG/MSIX_APP_ATTACH) and extract to the root of the c: drive or other.

Tip: before trying to run the application, you need to make sure you download the test certificate and install in the local machine's trusted root. You can find the certificate here: https://github.com/RMITBLOG/MSIX_APP_ATTACH/tree/master/Test%20Cert 

Download the Cim PowerShell scripts from GitHub: https://github.com/RMITBLOG/MSIX_APP_ATTACH and ensure that you have signed the scripts or set the execution policy to bypass.

Step four: Open CMD as a admin, navigate to the console application and run the command

cimutil.exe m "c:\<filename>.cim

This will mount the (.cim) and present a volume Guid. You will need this guid for the scripts as well as dismounting the (.cim) after use.

Step five: Update the json config file with the application folder name and volumeguid. Once this is completed correctly, you will be able to stage, register , deregister and destage the application using cim fs.

Step six: if you want to remove the (.Cim) just take the volume guid and use the following cmd.

cimutil.exe d "volume guid"


I trust you will all find the podcast interesting as well as testing out the new composite file system and running (.Cim) with MSIX App Attach. I am interested to here feedback and performance results.

Enjoy playing with Cimfs….

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