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Novell ZENworks Application Virtualization
4.2 Snapshotting applications
Most commercial applications require complex combinations of filesystem and registry entries in order to function
properly. In order to facilitate virtualization of these applications, ZENworks Application Virtualization can
snapshot application installations and automatically configure itself based on modifications made to the host
system during application setup.
Snapshotting
Snapshotting uses "before and after" images of the host machine to determine the virtual application
configuration:
1. Prior to installing the application, a "before" snapshot is taken. This captures the state of the host device
without the target application installed.
2. After installing the application, an "after" snapshot is taken. This captures all changes to the host device
during application installation. ZENworks Application Virtualization then computes the changes, or delta,
between the before and after snapshots, and inserts these changes into the configuration.
To use the snapshot feature:
1. Prepare the host device by either removing the target application and all dependencies, or copying ZENworks
Application Virtualization onto a "clean" machine.
2. Click on the Virtual Application tab on the ribbon bar and click Capture Before. This captures the
"before" snapshot image. Snapshotting iterates through the filesystem and registry, and therefore may take
several minutes to complete.
3. (Optional) We recommend you save the "before" snapshot before continuing. This allows you to skip this step
when snapshotting subsequent applications from the same clean machine image. To save the snapshot, click
on the down arrow underneath the Capture Before button and select Save Snapshot. Note that, while
ZENworks Application Virtualization automatically saves the last "before" snapshot that was captured, this
snapshot is reset once the Capture and Diff process is complete.
4. Install your application along with other files or settings you wish to be included in the virtual application. If
the application setup requests a reboot, be sure to save the "before" snapshot and then proceed with
the reboot.
5. On the Virtual Application tab on the ribbon bar, click Capture and Diff. This captures the "after"
snapshot, computes the delta between the two snapshots, and populates the virtual application with the delta
entries.
6. (Optional) Review the filesystem and registry entries, and remove any files or settings which are not required
for proper execution of your virtual application. Removing unused entries reduces virtual application size.
However, accidental removal of a required resource may cause your virtual application to no longer function
properly.
Saving snapshots
In many cases, the desired "before" snapshot remains fixed while many "after" snapshots are taken. ZENworks
Application Virtualization allows you to save the "before" snapshot image so that the snapshot does not need to be
re-captured each time. Because snapshotting may take several minutes, this significantly reduces the time
required to build virtual applications in this scenario.
To save the "before" snapshot, click on the down arrow underneath the Capture Before button on the Virtual
Application ribbon bar and select Save Snapshot. Select an appropriate filename and location and press
Save. Similarly, to load a saved snapshot, select the Load Snapshot menu item and navigate to the saved
snapshot file.
To clear the current "before" snapshot image, select the Clear Snapshot menu item.
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