An App Layer is a bootable software image (virtual disk) containing one or more applications that you can use in any number of Layered Images. When publishing a Layered Image, you can combine an App Layer with the OS Layer used to create it, other App Layers, and a Platform Layer.
To create an App Layer, you open the Create Layer wizard, deploy a Packaging Machine in your environment, then install the application(s). Once the application(s) are installed, you finalize the Layer.
A Packaging Machine is a VM where you install the application(s) that will be included in the Layer. The App Layering software creates the Packaging Machine in the location and using the credentials you supply by choosing the Platform Target (hypervisor) and selecting a Connector Configuration containing this information. If you don't yet have the Connector Configuration you need, you can add a new one, as described in the steps below.
To create an App Layer, you need:
Before you create an App Layer, you may also want to create resources that facilitate the application installation process. These resources are for temporary use during installation only, and will not be used to deliver the application.
If the application you install affects boot-level components, you'll need to restart the Packaging Machine as part of finalizing the layer or version.
Prerequisite Layers let you include existing App Layers on the Packaging Disk when creating or adding a version to an App Layer. Prerequisite Layers should only be used if they are required, since it is possible that the prerequisite applications will pull something into the Layer that is not required for the current application deployment, and which may cause conflict in the future.
Reasons to consider using Prerequisite Layers:
Note: Some of these issues can also be handled by putting the two applications in the same layer.
A Platform Layer is only required when creating App Layers on a hypervisor other than the one from which you imported your OS Layer.
If you are creating App Layers and Versions on a different hypervisor than the one you used to create your OS Layer, it is strongly recommended that you create a Platform Layer containing the hypervisor tools and hardware settings you need to seamlessly install and package applications in your environment.
You can include a Run Once script in an App Layer. This allows you to run a script the first time any Layered Image that includes the App Layer boots. If the App Layer is elastically layered, the Run Once script runs when the App Layer Disk is mounted. Run Once scripts are typically used for apps, such as MS Office, that require license activation on the first boot.
Select Layers > App Layers and select Create Layer in the Action bar. This opens the Create Layer wizard.
In the OS Layer tab, select the OS Layer you want to associate with this App Layer.
(Optional) In the Prerequisite Layers tab, if the application you are layering requires other App Layers to be present during installation, select the Include Prerequisite Layers check box, and pick the necessary App Layer(s).
In the Connector tab, choose a Connector Configuration that contains the credentials for the platform where you plan to build the Layer, along with the storage location. If the configuration you need isn't listed, add a New Connector Configuration and select it from this list.
Example: If you're using the Nutanix AHV environment to create the Layer, select the Nutanix AHV connector with the credentials and location required to access the location where you want to build the Layer.
In the Platform Layer tab you can select a Platform Layer containing the tools and hardware settings that you need to install and package an application during Layer creation. This selection is only used during layer creation. Once created, the Layer can be used in Layered Images published to any platform.
In the Packaging Disk tab, enter a file name for the Packaging Disk, and select the disk format. This disk will be used for the Packaging Machine (the VM) where you will install the application, as described in the next two sections.
In the Icon Assignment tab, select an icon to assign to the layer. This icon represents the layer in the Layers Module.
In the Confirm and Complete tab, review the details of the App Layer, enter a comment if required, and click Create Layer. Any comments you enter will appear in the Information view Audit History. Once the Packaging Disk has been created, the Task bar displays instructions to navigate to the Packaging Machine in Nutanix AHV.
Next, you can log into the Packaging Machine for your Layer, and install the software for the layer on it.
Back in the Management Console, expand the Tasks bar at the bottom of the UI, and double-click the Create App Layer task to see the full Task Description (example below).
When you've completed the Layer wizard, the App Layering software creates a Packaging Machine in your environment, in the location defined in the Connector Configuration. The Packaging Machine is a virtual machine where you install the software to be included in the layer.
Note: The Packaging Machine is a temporary VM that will be deleted once the new App Layer has been finalized.
Log into Nutanix Prism.
Back in the Management Console, expand the Tasks bar at the bottom of the UI, and double-click the Create App Layer task to see the full Task Description.
Use the instructions in the Task Description to navigate to the Packaging Machine in Nutanix Prism.
The Packaging Machine will be powered on.
When installing your application(s) on the Packaging Machine, leave each application as you want users to see it when they log in. The state of the applications when you finalize the layer is what users experience when they access the application. More guidance about this is included in the steps below.
Remote log in to the Packaging Machine in Nutanix AHV. Be sure to log in with the User account you used to create the OS in Nutanix AHV.
Install the applications, along with any drivers, boot-level applications, or files that the user will need with it.
If an application installation requires a system restart, restart it manually. The Packaging Machine does not restart automatically.
Make sure the Packaging Machine is in the state you want it to be for the user:
Once the application is installed on the Packaging Machine, it is important to verify that the Layer is ready to be finalized. To be ready for finalization, any required post-installation processing needs to be completed. For example, a reboot may be required, or a Microsoft NGen process may need to complete.
To verify that any outstanding processes are complete, you can run the Shutdown For Finalize tool (icon below), which appears on the Packaging Machine's desktop.
To use the Shutdown For Finalize tool:
The Layer is now ready to finalize.
Layer integrity messages let you know what queued tasks must be completed before a Layer is finalized.
A Microsoft NGen operation is in progress in the background.
Note: If a Microsoft NGen operation is in progress, you may be able to expedite it, as described in the next section.
NGen is the Microsoft Native Image Generator. It is part of the .NET system, and basically re-compiles .NET byte code into native images and constructs the registry entries to manage them. Windows will decide when to run NGen, based on what is being installed and what Windows detects in the configuration. When NGen is running, you must let it complete. An interrupted NGen operation can leave you with non-functioning .NET assemblies or other problems in the .NET system.
You have the choice of waiting for the NGen to complete in the background, or you can force the NGen to the foreground. You can also check the status of the NGen operation, as described below. However, every time you check the queue status, you are creating foreground activity, which might cause the background processing to temporarily pause.
Forcing the NGen to the foreground will allow you to view the progress and once the output has completed, you should be able to finalize the layer.
Force an NGen operation to the foreground.
Normally, NGen is a background operation and will pause if there is foreground activity. Bringing the task into the foreground can help the task to complete as quickly as possible. To do this:
Open a command prompt as Administrator.
Go to the Microsoft .NET Framework directory for the version currently in use:
Enter the NGen command to execute the queued items:
ngen update /force
This brings the NGen task to the foreground in the command prompt, and lists the assemblies being compiled.
Note: It’s okay if you see several compilation failed messages!
Check the status of an NGen operation
Open a command prompt as Administrator.
Check status by running this command:
ngen queue status
When you receive the following status, the NGen is complete, and you can finalize the Layer.
The .NET Runtime Optimization Service is stopped
Once the software has been installed and the Packaging Machine has been verified and shut down, you are ready to finalize the layer.
Note: When you finalize a Layer, the Packaging Machine may be deleted to minimize storage space used.
When the Layer has been verified and is ready to finalize:
Version - (Required) This can be the version of the application or a version you assign to the Layer. This value is displayed in the Details view of the Layer. Keep in mind that you'll add a new version to this layer whenever you update the app(s) included in it, and this is where the version will be described.