Pro edition. App Attach delivers an MSIX app to Azure Virtual Desktop or Windows 365 session hosts by mounting it from a disk image instead of installing it.
Step 1: MSIX Source #
Upload one of the following:
- a ready-made
.msixor.msixbundle, or - the application files. The wizard then builds and signs the MSIX for you.
Step 2: Image Format #
| Field | Description |
|---|---|
| MSIX package | Choose an uploaded .msix (picked automatically if there is only one). Leave it empty to build the MSIX from the uploaded application files. |
| Image format | VHDX (recommended for most hosts), VHD (legacy) or CIM (fastest mount on Windows 11 hosts) |
| Image size (MB) | Size of the VHDX or VHD (default 512 MB). It must be about 1.2 × the app size plus 50 MB. Not used for CIM. |
About CIM images:
- A CIM image consists of several files:
{name}.cimplusobjectid_*andregion_*files. Always copy all of them together. - The generated scripts need the
CimDiskImagePowerShell module on the session host. AVD’s built-in App Attach mounts CIM images without this module. - Use VHDX for Windows Server 2019 and 2022 hosts.
A ready-made .msix that you upload is checked before it is used:
- Unsigned packages are rejected.
- Packages whose publisher does not match their signature are rejected.
- If the signer is not trusted on this machine, you get a warning.
Step 3: Signing #
This step offers the same certificate and timestamp settings as the MSIX wizard. It applies when the wizard builds the MSIX itself. The public certificate (.cer) is saved next to the image, and the Stage script trusts it automatically on the session host.
Step 4: Lifecycle Scripts #
App Attach uses four scripts:
| Script | Runs as | When |
|---|---|---|
| Stage | Administrator | At host startup: mounts the image and stages the app |
| Register | User | At sign-in: registers the app for the user |
| Deregister | User | At sign-out |
| Destage | Administrator | At host shutdown: removes the app and dismounts the image |
Working default scripts are generated for you. To change one, click Customize:
- You can use Insert snippet… for logging or error handling.
- Reset to generated default undoes your changes.
For AVD host pools, Microsoft recommends the built-in App Attach feature in the Azure portal. In that case you only need the image.
Step 5: Metadata #
Enter the Display name (required) and the Version.
Step 6: Preview & Build #
The step shows the validation results and the image plan, and checks this machine:
- If the
msixmgrtool is missing, the build is blocked and the reason is explained. - Creating a disk image needs administrator rights. If the app is not running as administrator, the Request admin rights (UAC) switch appears (on by default). Windows shows an administrator prompt when the build starts. Choose Yes in that prompt.
Click Build App Attach Image.
Result:
- the image (
.vhdx,.vhd, or the.cimfile set) - the four lifecycle scripts
{name}.cer
App Attach images are built to disk and cannot be uploaded from the app. Copy them to your file share yourself.