App Layering


XenServer is a highly optimized hypervisor platform for Citrix Virtual Apps and Desktops, enabling Windows and Linux Virtual Apps and Desktops delivery to any device and hundreds of employees in just minutes.

Before you start

You can use your XenServer environment to create Layers and publish layered images. Each Connector Configuration accesses a specific storage location in your XenServer environment. You might need more than one XenServer Connector Configuration to access the correct location for each purpose. Further, you can publish each layered image to a location convenient to the system you provision with the published image. For more information about Connectors and Connector Configurations, see Connector configurations.

With the XenServer architecture, you can interact with individual servers or a cluster of servers instead of a central management server. You can manage XenServer by using command-line access or management software, such as XenCenter. You can install XenCenter on your desktop and connect individually to each host or a cluster of hosts.

If this is your first time using App Layering

If you want to create App Layers by using a XenServer virtual machine, you need a XenServer Connector within App Layering. When you publish layered images to XenServer, you also need a Connector Configuration for each of your publishing locations.

Creating a layer and publishing a layered image prompts you to select a connector configuration. If you don’t yet have the right connector configuration for the task, you can create one by clicking Add Connector Configuration on the Connectors page.

Required information for XenServer Connector Configuration settings Configuring a connector for XenServer lets you browse for the XenCenter Server, Data Store, and Host to use for a new configuration.


The fields are case-sensitive. Any values that you enter manually must match the case of the object in XenServer, or the validation fails.

  • XenServer Configuration Name: A useful name to help identify and keep track of this connector configuration.
  • XenServer Address: The name of the XenServer host with which the appliance integrates.
  • User Name and Password: The credentials for the account that the appliance uses to connect to the XenServer.
  • Use Secured Communications: SSL encryption for the API connection traffic between the App Layering Connector and XenServer. This field is selected by default.
  • Virtual Machine Template: The virtual machine template for cloning. The list of choices contains custom virtual machine templates only, rather than actual virtual machines or any of the built-in templates. The selected template must not have any disks attached and must have at least one network card attached. If it does not, you see an error when trying to validate or save the configuration.
  • Storage Repository: The storage repository for the disk that uploads. The list is filtered to show only repositories that can contain virtual hard disks (ISO repositories are filtered out).
  • Layer Disk Cache Size in GB (optional): Specifies the size of the cache allowed for the layer. By default, the allowed cache size is 250 GB.
  • Use HTTPS for File Transfers: Encrypts the image file transfers. HTTPS is selected by default for more secure uploads and downloads but can be cleared for increased performance. This does not apply when you enable Offload Compositing.
  • Offload Compositing (recommended): Enables the layer packaging or image publishing process to run on the specified Hypervisor server. This feature increases performance and it allows you to use VMDK disk format and either BIOS or UEFI virtual machines. With UEFI, you can also use Secure Boot if it’s enabled on the Hypervisor.
  • ISO Storage Repository: Repository for the disks that Offload Compositing uploads. The list is filtered to show only ISO repositories. SMB and NFS are supported.
  • ISO Share Path: Automatically populates for selected ISO storage repository by the ISO share path configured. For display only.
  • ISO Share Username: User name for the selected ISO Share. Only valid for SMB ISO Share. NFS ISO Share does not support a user name or password.
  • ISO Share Password: Password for the select ISO share. Only valid for SMB ISO Share. NFS ISO Share does not support a user name or password.

When Offload Compositing is selected:

  • If you provide a template configured for BIOS or UEFI, the resulting virtual machine is the type that you chose.
  • If you provide a template with UEFI-Secure Boot enabled and selected, the resulting virtual machine is the UEFI-Secure Boot.

When Offload Compositing isn’t selected:

  • If you provide a template configured for BIOS, the resulting virtual machine is BIOS.
  • If you provide a template configured for UEFI and when you attempt to save the connector configuration, an error is displayed.

Virtual Machine folder Virtual machines created by the XenServer connector, whether packaging machines or layered images, can use either folders or tags to organize the virtual machines. XenServer allows you to organize virtual machines by folder or by tag. These organizational tools are optional when creating and managing virtual machines through XenCenter or other tools. Although XenServer connector configurations do not allow you to specify folders or tags, the virtual machines created by the XenServer connector, both packaging machines and published layered images, can use both organizational tools.

Caching tags If the template specified in the XenServer connector configuration has any tags, then those tags are carried over to any virtual machine cloned from that template. All packaging virtual machines or published layered images are tagged with the same tags that the template has. Also, the XenServer connector adds three tags.

  • App Layering - All virtual machines created by the XenServer connector can be found by this tag regardless of their purpose or image.
  • Purpose Tag - All packaging machines are tagged with App Layering Packaging Machine while all published layered image virtual machines are tagged with App Layering Published Images.
  • Image or Layer Name - All packaging machines are tagged with the layer name for the layer for which they are generated, while all published layered images are tagged with the template image name. If you are using XenCenter, you can view your virtual machines by tag by selecting Organization Views and then selecting By Tag.

Folder By default, virtual machines created by the XenServer Connector are not placed in a folder. However, if the template specified in the XenServer Connector Configuration resides in a folder, then any virtual machine that the Connector creates from that template also resides in the same folder. All packaging VMs and published layered images are placed in that same folder. There are no separate subfolders for packaging VMs or published layered images.

Machine network connectivity The virtual network settings of the source template specified in the XenServer Connector Configuration are carried over when creating any VMs through the XenServer Connector. There is no option in the Connector Configuration UI to override the network settings.

XenServer Clusters The XenServer Connector does not yet work correctly with XenServer clusters. If the host specified in the configuration is part of a cluster, then it must be the master host in the cluster for the connector to work. However, this means that anytime the master XenServer host goes down and a new master is elected, the XenServer configuration must be updated.

Create a Connector Configuration

To enter the values:

  • Enter the first three Connector fields manually. After validating the credentials in those fields, you can select values for the remaining fields from the drop-down menus.
  • To enter values manually, click to put the cursor in the field and type the value, making sure that the case matches the value in XenServer.
  • To select a value from a drop-down list, do the following:
    • Click once to put the cursor in the field.
    • Click a second time to display the list of possible values.

To add a Connector Configuration

  1. Click the Connectors page.
  2. Click Add Connector Configuration. A dialog box opens.
  3. Select the Connector Type for the platform and location where you are creating the layer or publishing the image.
  4. Click New to open the Connector Configuration page.
  5. Type the configuration Name, XenServer address, user name, password, and setting for the Use Secured Communications check box. For more information, see the above field definitions.
  6. Click CONNECT below the XenServer Configuration fields. The Virtual Machine Clone Settings fields are then enabled if the user name and password are correct.


    If there is a certificate error, the following error message is displayed: One or more problems with the service certificate were found. You can enable them to be ignored, or you must update the certificate on the server. You can click Ignore Certificate Errors and Continue.

  7. Select the required Virtual Machine Template.
  8. Select the Storage Repository.
  9. Ensure Packaging Cache Size in GB is set to the desired value (or use default). Setting the value to 0 results in no caching.
  10. Select the setting for Use HTTPS for File Transfers.
  11. Select the setting for Use Offload Compositing.
  12. If Use Offload Compositing is selected, select ISO Storage Repository. The ISO Share Path is auto-populated.
  13. If an SMB ISO share is selected, enter the SMB ISO share user name and password.
  14. Click CONFIRM AND COMPLETE. A configuration summary is displayed.
  15. Click Save. If no errors are displayed, the new connector configuration is saved and displayed on the Connector page.