Citrix App Layering - OS Test

Citrix App Layering lets you package any Windows application as a virtual disk, layer and deliver it, installation-free, to pooled desktops and session hosts. With App Layering, you can:

  • Install and manage a single copy of your Windows operating system and a single copy of each of your applications in layers. A layer is simply a container for the file system objects and registry entries unique to that layer.
  • Select any combination of layers to create layered Images that are deployable as desktops or session hosts.
  • Deploy the layered images to virtual machine desktops and session hosts, making the applications available to users.

Citrix App Layering enables IT administrators to deliver applications that look, act and feel as if they are installed locally in the VM/Golden Image, but these applications are actually stored as separate manageable objects in their own virtual disks. With Citrix App Layering, any application can be separated from the Windows OS. As a result, IT administrators will only have a single OS Layer to manage regardless of the number of machine configurations (pools, silos, delivery groups). This simplifies the environment while reducing management time/complexity and the costs associated with OS and app management. Application layers can be attached to the virtual machine in one of two ways:

  1. App Layers can be combined with an OS Layer, in a process called image publishing, and pushed to existing provisioning systems such as Citrix Provisioning Services, Citrix Machine Creation Services, or VMware View Composer;
  2. App Layers can be attached to a VM at user login based on user AD group membership and app assignments. Each user can also receive a unique “Personalization Layer." This Personalization Layer will contain unique information for that user that will include things like local Windows profiles, application settings, files and folders created by the user and even user-installed applications.

The App Layers can be attached to persistent and non-persistent desktops in the VDI environment. A persistent virtual desktop, also known as a dedicated desktop, is a unique operating system image created for each user. The customized App Layers are attached to a user when he/she logs in to the persistent desktop at the very first time. These customized layers and specific settings will be available to the user until he/she reboots the desktop. On the other hand, a non-persistent desktop, also called stateless desktop, cannot be personalized for every user and can be shared among multiple users to the environment. The App Layering makes it possible to save user data and user-installed software even in non-persistent deployments. In non-persistent deployments, the App Layers are attached to every user based on their customization whenever he/she logs in. These layers and the corresponding settings will be available until he/she logs off from the session. Once the user logs out from the non-persistent desktop, the layers will be detached and the desktop will be ready for use by another user.

Regardless of the types of virtual desktops to which the App Layering is done, it is important that the App Layers should be fully attached without adding a significant delay to the logon process. If, for any reason, App Layering failed or takes more time during the logon process, then the logon process may fail or take longer time to complete. This in turn will impact the productivity of the users and overall user experience with the virtual server. Particularly, if the users experience frequent delays in the non-persistent environment, then the productivity and experience during every session initiated from the non-persistent desktop will be seriously impacted. Therefore, it is imperative that administrators keep track of the time taken for attaching the App Layers and the layers attached during every user's session. This can be easily tracked using the Citrix App Layering - OS test.

This test helps administrators to promptly find out if there is a delay during the App Layering process and enables them to take remedial measures before the delay causes serious impact on the productivity and user experience.


This test is applicable only for the App Layering enabled desktops that are hosted by the Citrix Hypervisor server.

Target of the test : A Citrix Hypervisor

Agent deploying the test : An internal agent

Outputs of the test : One set of results for each user connected to the Citrix hypervisor that is to be monitored.

Configurable parameters for the test
Parameter Description

Test period

How often should the test be executed.


The host for which the test is to be configured.


The port at which the specified host listens. By default, this is NULL.

Xen User, Xen Password and Confirm Password

To enable the eG agent to connect to the XenServer API for collecting statistics of interest, this test should login to the target hypervisor as a root user. Provide the name of the root user in the Xen User text box. Root user privileges are mandatory when monitoring a XenServer 5.5 (or below). However, if you are monitoring XenServer 5.6 (or above) and you prefer not to expose the credentials of the root user, then, you have the option of configuring a user with pool-admin privileges as the Xen User. If you do not want to expose the credentials of a root/pool-admin user, then you can configure the tests with the credentials of a Xen User with Read-only privileges to the XenServer. However, if this is done, then the Xen Uptime test will not run, and the Xen CPU and Xen Memory tests will not be able to report metrics for the control domain descriptor. To avoid such an outcome, do the following before attempting to configure the eG tests with a Xen User who has Read-only privileges to the Citrix Hypervisor:

  • Modify the target hypervisor's configuration in the eG Enterprise. For this, follow the Infrastructure -> Components -> Add/Modify menu sequence, pick Citrix Hypervisor as the Component type, and click the Modify button corresponding to the target hypervisor.
  • In the MODIFY COMPONENT DETAILS page that then appears, make sure that the os is set to Xen and the Mode is set to SSH.
  • Then, in the same page, proceed to provide the User and Password of a user who has the right to connect to the XenServer console via SSH.
  • Then, click the Update button to save the changes.

Once this is done, you can configure the eG tests with the credentials of a Xen User with Read-only privileges.

The password of the specified Xen User needs to be mentioned in the Xen Password text box.

Then, confirm the Xen Password by retyping it in the Confirm Password text box.


By default, the Citrix Hypervisor is not SSL-enabled. This indicates that by default, the eG agent communicates with the target hypervisor using HTTP. Accordingly, the SSL flag is set to No by default. If you configure the target hypervisor to use SSL, then make sure that the SSL flag is set to Yes, so that the eG agent communicates with the target hypervisor using HTTPS. Note that a default SSL certificate comes bundled with every Citrix Hypervisor installation. If you want the eG agent to use this default certificate for communicating with an SSL-enabled Citrix Hypervisor, then no additional configuration is required. However, if you do not want to use the default certificate, then you can generate a self-signed certificate for use by the target hypervisor. In such a case, you need to explicitly follow the broad steps given below to enable the eG agent to communicate with the target hypervisor via HTTPS:

  • Obtain the server-certificate for the Citrix Hypervisor
  • Import the server-certificate into the local certificate store of the eG agent

For a detailed discussion on each of these steps, refer to the Troubleshooting section of this document.

Inside View Using

By default, this test communicates with every VM remotely and extracts “inside view” metrics. Therefore, by default, the Inside View Using flag is set to Remote connection to VM (Windows).

Typically, to establish this remote connection with Windows VMs in particular, eG Enterprise requires that the eG agent be configured with domain administrator privileges. In high-security environments, where the IT staff might have reservations about exposing the credentials of their domain administrators, this approach to extracting “inside view” metrics might not be preferred. In such environments therefore, eG Enterprise provides administrators the option to deploy a piece of software called the eG VM Agent on every Windows VM; this VM agent allows the eG agent to collect “inside view” metrics from the Windows VMs without domain administrator rights. Refer to Configuring Windows Virtual Machines to Support the eG Agent’s Inside View Using the eG VM Agent for more details on the eG VM Agent. To ensure that the “inside view” of Windows VMs is obtained using the eG VM Agent, set the Inside View Using flag to eG VM Agent (Windows). Once this is done, you can set the Domain, Admin User, and Admin Password parameters to none.

Domain, Admin User, and Admin Password, and Confirm Password

By default, this test connects to each virtual guest remotely and attempts to collect “inside view” metrics. In order to obtain a remote connection, the test must be configured with user privileges that allow remote communication with the virtual guests. The first step towards this is to specify the DOMAIN within which the virtual guests reside. The ADMIN USER and ADMIN PASSWORD will change according to the DOMAIN specification. Discussed below are the different values that the DOMAIN parameter can take, and how they impact the ADMIN USER and ADMIN PASSWORD specifications:

  • If the VMs belong to a single domain : If the guests belong to a specific domain, then specify the name of that domain against the DOMAIN parameter. In this case, any administrative user in that domain will have remote access to all the virtual guests. Therefore, an administrator account in the given domain can be provided in the ADMIN USER field and the corresponding password in the ADMIN PASSWORD field. Confirm the password by retyping it in the CONFIRM PASSWORD text box.
  • If the guests do not belong to any domain (as in the case of Linux guests) : In this case, specify "none" in the DOMAIN field, and specify a local administrator account name in the ADMIN USER below.

    Prior to this, you need to ensure that the same local administrator account is available or is explicitly created on each of the virtual machines to be monitored. Then, proceed to provide the password of the ADMIN USER against ADMIN PASSWORD, and confirm the password by retyping it in the CONFIRM PASSWORD text box.

    If key-based authentication is implemented between the eG agent and the SSH daemon of a Linux guest, then, in the ADMIN USER text box, enter the name of the user whose <USER_HOME_DIR> (on that Linux guest) contains a .ssh directory with the public key file named authorized_keys. The ADMIN PASSWORD in this case will be the passphrase of the public key; the default public key file that is bundled with the eG agent takes the password eginnovations. Specify this as the ADMIN PASSWORD if you are using the default private/public key pair that is bundled with the eG agent to implement key-based authentication. On the other hand, if you are generating a new public/private key pair for this purpose, then use the passphrase that you provide while generating the pair. For the detailed procedure on Implementing Key-based Authentication refer to Troubleshooting the Failure of the eG Remote Agent to Connect to or Report Measures for Linux Guests.

  • If the guests belong to different domains - In this case, you might want to provide multiple domain names. If this is done, then, to access the guests in every configured domain, the test should be configured with the required user privileges; this implies that along with multiple DOMAIN names, multiple ADMIN USER names and ADMIN PASSWORDs would also have to be provided. To help administrators provide these user details quickly and easily, the eG administrative interface embeds a special configuration page.

    To access this page, simply click on the Click here hyperlink that appears just above the parameters of this test in the test configuration page. To know how to use the special page, refer to Configuring Users for VM Monitoring.

  • If the INSIDE VIEW USING flag is set to ‘eG VM Agent (Windows)’ - In this case, the inside view can be obtained without domain administrator privileges. Therefore, set the domain, admin user, and admin password parameters to none.

Ignore VMs Inside View

Administrators of some high security XenServer environments might not have permissions to internally monitor one/more VMs. The eG agent can be configured to not obtain the 'inside view' of such ‘inaccessible’ VMs using the IGNORE VMS INSIDE VIEW parameter. Against this parameter, you can provide a comma-separated list of VM names, or VM name patterns, for which the inside view need not be obtained. For instance, your IGNORE VMS INSIDE VIEW specification can be: *xp,*lin*,win*,vista. Here, the * (asterisk) is used to denote leading and trailing spaces (as the case may be). By default, this parameter is set to none indicating that the eG agent obtains the inside view of all VMs on a Citrix Hypervisor host by default.


While performing VM discovery, the eG agent will not discover the operating system of the VMs configured in the IGNORE VMS INSIDE VIEW text box.

Exclude VMs

Administrators of some virtualized environments may not want to monitor some of their less-critical VMs - for instance, VM templates - both from 'outside' and from 'inside'. The eG agent in this case can be configured to completely exclude such VMs from its monitoring purview. To achieve this, provide a comma-separated list of VMs to be excluded from monitoring in the EXCLUDE VMS text box. Instead of VMs, VM name patterns can also be provided here in a comma-separated list. For example, your EXCLUDE VMS specification can be: *xp,*lin*,win*,vista. Here, the * (asterisk) is used to denote leading and trailing spaces (as the case may be). By default, this parameter is set to none indicating that the eG agent obtains the inside and outside views of all VMs on a virtual host by default. By providing a comma-separated list of VMs/VM name patterns in the EXCLUDE VMS text box, you can make sure the eG agent stops collecting 'inside' and 'outside' view metrics for a configured set of VMs.

Ignore Winnt

By default, the eG agent does not support the inside view for VMs executing on Windows NT operating systems. Accordingly, the IGNORE WINNT flag is set to Yes by default.

Report by User

This flag is set to Yes by default. The value of this flag cannot be changed. This implies that the virtual machines in target VDI environments will always be identified using the login name of the user. In other words, in VDI environments, this test will, by default, report measures for every username_on_virtualmachinename. .

Report Powered OS

This flag becomes relevant only if the report by user flag is set to ‘Yes’.

If the report powered os flag is set to Yes (which is the default setting), then this test will report measures for even those VMs that do not have any users logged in currently. Such guests will be identified by their virtualmachine name and not by the username_on_virtualmachinename. On the other hand, if the report powered os flag is set to No, then this test will not report measures for those VMs to which no users are logged in currently.

DD Frequency

Refers to the frequency with which detailed diagnosis measures are to be generated for this test. The default is 1:1. This indicates that, by default, detailed measures will be generated every time this test runs, and also every time the test detects a problem. You can modify this frequency, if you so desire. Also, if you intend to disable the detailed diagnosis capability for this test, you can do so by specifying none against DD FREQUENCY.

Detailed Diagnosis

To make diagnosis more efficient and accurate, the eG suite embeds an optional detailed diagnostic capability. With this capability, the eG agents can be configured to run detailed, more elaborate tests as and when specific problems are detected. To enable the detailed diagnosis capability of this test for a particular server, choose the On option. To disable the capability, click on the Off option.

The option to selectively enable/disable the detailed diagnosis capability will be available only if the following conditions are fulfilled:

  • The eG manager license should allow the detailed diagnosis capability
  • Both the normal and abnormal frequencies configured for the detailed diagnosis measures should not be 0.
Measurements made by the test
Measurement Description Measurement Unit Interpretation

App Layering duration

Indicates the amount of time taken for attaching the App Layered disks for this user.


Ideally, the value of this should be very low. An increase in the value of this measure may indicate the logon delay for the users.

Have App Layered disks been attached successfully?

Indicates whether/not the App Layered disks have been attached to this user successfully.


The values that this measure can report and their corresponding numeric values are tabulated below:

Measure Value

Numeric value
No 0
Yes 1



By default, this measure reports the above-mentioned Measure Values listed in the table to indicate whether or not the App Layered disks have been attached to this user successfully. The graph of this measure however is represented using the numeric equivalents only.

Use the detailed diagnosis of this measure, to know the revision and name of the layered disks attached to the user sessions and the name of attached files.