Blog Post - PVS Automatic Updates

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					How to Automatically Update Provisioning Services vDisks
Provisioning Services (PVS) solves many of the existing problems of datacenters and desktop
administrators by reducing the number of unique images that need to managed. Rather than dealing
with application installs, conflicts, patches and errors on hundreds of different servers and desktops,
they can deal with a single streamed golden image that remains pristine regardless of the changes made
by users.

However, even though this new model solves many of the issues that have been plaguing IT
administrators for years, a new concern comes up that I’m asked by every single client wanting to
implement Provisioning Server: “If I have a pristine image, how do I deal with antivirus updates and
patching?”

I could send them to the admin guide and point them to page 109, which gives detailed instructions on
how to do exactly that. It goes, on a high level, something like this:

       Load a machine with a copy of the production vDisk in private mode
       Make your changes
       Shut it down and put it into standard mode
       Finally, increment the version number

This process is easy to do manually, and if you only have to add updates every once in a while, there’s no
problem. However, we all know Microsoft comes up with security updates on an almost weekly basis,
and new anti-virus definitions come out nightly. Most companies aren’t comfortable leaving machines
not protected for extended periods of time, and IT administrators don’t want to spend time doing a
manual, repetitive task on a daily basis. Add in a few different vDisks for different workloads, and this
can quickly become a time consuming process.

Enter Workflow Studio. Workflow Studio (WFS) is designed to reduce repetitive tasks into easy-to-
manage workflows that can be run either on-demand or on a scheduled basis. Using Workflow Studio
and PVS’s built-in CLI, we were able to create a script that automates the entire process of updating
vDisks, allowing for easy nightly or weekly scheduling with less chance for human error.

In order to be device/hypervisor agnostic, the script utilizes an always-on machine designated as an
“update” machine, which allows PVS to use its own functionally to restart the machine when necessary.
Updates can come in and automatically be implemented during the course of the day or week, and
applications can be added or removed by the vDisk admin. Then, at the scheduled point or manual call,
the script shuts down the server, makes a copy for future updates, and switches out the disks using the
Auto-Update feature. After the next reboot, desktops will switch to the newest disk, no additional
manual intervention required.

Additionally, the “update” machine can be given a “personality” that then executes scripts inside the
image that aren’t executed on other machines – such as perhaps automatically copying files from a
share, or enabling Microsoft’s Auto-Update, or any number of other actions. Finally, while Workflow
Studio is a component of making the script function appropriately, it has the added benefit of allowing
role-based access to the Workflow, as well as built-in scheduling. However, if Workflow Studio cannot
be deployed, then the components of the script can be broken apart and used solely with Windows
Scheduler.

Grab the script here (at the Citrix Developer Network). If you have questions, comments, or ideas for
improvement leave me a comment or ping me on Twitter @mikebogo.

				
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posted:3/31/2012
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