App Layering

Create the OS layer

An OS layer includes the software and settings for the operating system that you deploy in layered images. The OS layer is necessary for creating:

  • Platform layers
  • App layers
  • Layered images


In the new UI, the only way to create an OS layer is by importing it with the ImportOSLayer.ps1 utility. You can no longer create OS layers through the management console. For more details, contact your Citrix representative.

About importing the operating system for the layer

The only way to import the operating system is to run the OS import script, included in the OS Machine Tools download:


The advantages of using an import script include:

  • Better performance: The operating system import runs faster.

  • Unified Extensible Firmware Interface (UEFI) machine and Secure Boot support.


Before creating the OS layer, be sure to:

Considerations for your OS layer

  • To deploy Windows patches and updates, you can simply add a version to the layer. You can easily revert to the previous version of the layer, if necessary.
  • You can select any version of the layer to use in an image template, and therefore in the published images.
  • You can update the OS using Windows Update, Windows Server Update Services (WSUS), or offline standalone update packages. Do not use tools like SCCM.
  • Platform and app layers are tied to the specific OS layer that you use to create them, though not to a specific version of the layer. When you add versions to the OS layer, the dependent app and platform layers continue to work.
  • Windows updates must be applied to the OS layer before you update any other layers.

Import the OS using the ImportOSLayer.ps1 script

This procedure explains how to import the OS for your new OS layer using the ImportOsLayer.ps1 script.

If you have downloaded and expanded the App Layering OS Machine Tools onto your OS image, the ImportOsLayer.ps1 has been copied to c:\windows\setup\scripts.

Run the script

To import the OS:

  1. Run the ImportOsLayer.ps1 PoSH script as administrator:

    C:\Windows\Setup\scripts\ImportOsLayer.ps1 -ElmAddress <Ip Address> [-IgnoreCertErrors]
    C:\Windows\Setup\scripts\ImportOsLayer.ps1 -ElmAddress <FQDN> [-IgnoreCertErrors]


    • ElmAddress is the IP Address or FQDN of the App Layering appliance. It specifies where the new OS layer is created.
    • IgnoreCertErrors ignores certification errors when the script communicates with the App Layering appliance.
  2. The ImportOsLayer.ps1 script prompts you for the credentials to connect to the App Layering appliance (referred to as the ELM in the script). The script uses your credentials to create a session on the appliance.

  3. The script then prompts you for details about the new OS layer:

    • LayerName (required)
    • VersionName (required)
    • LayerSizeGib (required, but defaults to 60 GB)
    • LayerDescription (optional)
    • VersionDescription (optional)
    • Comment (optional)

    Once you’ve entered the required information, the script reboots the system into the compositing engine, imports the OS, and builds the layer. Monitor the progress of the job in the management console.

    When the compositing engine is finished (success or failure), it reboots back into the Windows OS image.

Create the OS layer