Updating and Writing XML Files with PowerShell

Manipulating XML files with PowerShell is something that we’re having to accomplish more and more internally. Microsoft App-V 5.0 and RES Workspace Manager utilise XML files extensively. Whilst we can manually tweak them, there’s nothing like automating things for consistency and speed!

I have seen a lot of “rip and replace” and “find and replace” script examples, but ensuring that the correct elements/nodes are added in the correct place can be troublesome. The only real option is to utilise the built-in .Net Framework XML objects. Hopefully this post will lay the basis for some more App-V 5.0 focused blogs in the future Open-mouthed smile.

There are lots of forum posts out there that detail snippets of information, but a lot of it is trial and error. As a starting point you might want to read up here first. Reading XML files is one thing, but as the previous article mentions, inserting (multiple) elements can be quite convoluted. Note: I’m using the XmlDocument .Net object here but it is possible to utilise other .Net classes, e.g. XPath and/or XDocument.

Here is the example we’ll use in this post. Apologies; the XML formatting is stripped by the plugin:

Creating XML Elements

If we wish to add a new employee record to the above document, we need to create a new XML element (or node). Firstly we need to load the XML document:

Now we can create our new element/node, append it to the parent reference and save it:

To shorten this we can just use this (see here for more information on the CreateElement method):

If we examine the resulting XML file we’ll find the following (note the new empty element):

 Adding XML Attributes

To add the ID attribute tag in the XML document, we need to create a new XmlDocument Attribute and then attach it to our newly created element. We can create an XmlDocument attribute on our element with the following code:

Now our resulting XML file looks like this:

Adding Nested XML Elements

Knowing how to add elements we can simply create our sub elements and attach them to our newly created parent reference:

The resulting XML file now looks like:

Adding XML Text Nodes

Unbeknownst to me, when you have text within an element tag, i.e. <name>Iain Brighton</name>, this is known as a text node (at least in XDocument speak). This is probably the bit that took longest to work out.

To add the text node we can use the following code:

Et voilà!

 Full PowerShell Code Snippet

Here is the full code listing:

PVS Image Management

There has been a bit of banter on the Twittersphere about how people manage and document their PVS images. It was suggested (by more than just me Smile) that RES Automation Manager could be utilised for this task. This post is not a best practice guide as to how to create, update or document your images, rather a use case on how and why we use/recommend RES Automation Manager. Heaven forbid, you might even decide to do away with Provisioning Services as a result. Either way RES Automation Manager will play very nicely with or without PVS but I couldn’t fit it into 140 characters!

Provisioning Services Private Image Management

Maintaining the gold or private mode PVS image can be a complex task for a number of reasons. Simplifying any of these potential hurdles can only be a good thing, right?

  1. A certain level of skill is required to both create and maintain images. There are numerous tasks that need to be completed and in some cases, performed in a particular order. As a result, this task is typically left or assigned to the senior administrators.
  2. Application upgrades can taint or stain the master image. Some applications require an uninstallation of the old version and installation of the new product MSI. I don’t need to tell you that uninstallers are not always reliable or clean everything out when run!
  3. How are changes to the gold image documented to ensure that they’re incorporated into all other PVS images? It is typical that there will be more than one image for deployment. For example, hardware differences will typically require separate images.
  4. Ad-hoc and emergency changes can wreak havoc with your PVS images. How quick and easy is it to push an update out to 100 XenApp servers streamed from a central image? If we make changes whilst the servers are running then they’ll be lost when the write cache is erased meaning we either have to reapply this change after every reboot or update our gold image pronto! This will get a lot more interesting if the servers are rebooted on a nightly basis and the write cache cleaned!

RES Automation Manager

If know me by now, you probably know that I’m going to say that RES Automation Manager is the answer to all your prayers! Now whilst it can certainly address the above “issues” (and I would recommend it in conjunction with Provisioning Services any day of the week) there are other processes and solutions that may address one or more of the above and deploying RES Automation Manager won’t automagically fix them. A good example of this is documentation. If your internal processes mandate that all changes are documented and you bypass this process, there is nothing to stop you bypassing this process even if Automation Manager is installed!

What RES Automation Manager Won’t Do

Thought I’d better get this bit out of the way before you get all the way to the end and are disappointed! RES Automation Manager is a Run Book Automation tool and not an imaging/deployment tool. This means that we cannot (directly) deploy an Operating System from RES Automation Manager. Fortunately for us there are many technologies out there that can, e.g. Windows Deployment Services/Microsoft Deployment Toolkit which BTW can by combined with RES Automation Manager – take a look at this White Paper. Why reinvent the wheel?!

What RES Automation Manager Will Do

So once we have our Operating System deployed and the RES Automation Manager agent installed (we can do this with WDS/MDT as mentioned earlier) what benefits will this give us? Well, at a simplistic level, RES Automation Manager can automate the entire server configuration and application deployment process. This process can also include installing XenApp and XenApp Prep as well as any other applications. This obviously takes some additional time but gives us a clean, repeatable process for deploying a XenApp server from scratch. It’s a strategic decision and not a tactical one!

Why is this important? Typically it comes down to issues #2 and #3 so let’s take them one at a time..

Issue #1

RES Automation Manager can reduce this complexity by removing Provisioning Services altogether. I’m not suggesting that you remove this from your infrastructure. Not even for one minute. However, if you don’t need to have a clean image after every reboot getting shot of PVS maybe an option? We have automated the complete server deployment and can typically provision a new server in a few hours from start to finish; Operating System, XenApp and applications. OK it’s a few hours of time, but there is no user interaction required. I’m guessing that it’s probably not that often that you need to add a new server within 30 minutes?

This benefits the typical IT department as these are now regular servers. They’re supported in the same way as other servers and they have a proper OS install etc. There are downsides too. Now we need to patch and maintain multiple OS instances and not just one master image. Isn’t this part of the reason you deployed Provisioning Services in the first place?

Issue #2

By having a repeatable process for building our XenApp server(s) from scratch we can avoid tainting our image. If we need to cut a new image then we can deploy a completely clean server and deploy the required applications as required. We don’t need to uninstall and reinstall or upgrade applications. I’m not advocating this as a best practice, but I know lots of admins that are a lot happier with this process. It doesn’t need to be performed for all updates, but you now have an option as to whether you update the master image or cut a new one. If you have not automated the entire deployment and configuration process, recreating a new image from scratch probably doesn’t make you feel warm and fluffy inside!

When you finally get run over by a bus (it’s going to happen one day as everyone keeps saying it) pretty much anyone with ounce of intelligence can deploy a new server or reverse engineer the Modules and Tasks in the Run Book to discover how things are tied together.

Issue #3

By virtue of automating the entire configuration and deployment process with RES Automation Manager, you have actually documented every step in the process. RES Automation Manager includes the ability to create an Instant Report of any or all Run Books, Projects and/or Modules. These reports are very detailed (small example here) and typically run to 1,000+ pages. For us consultants, this feature alone is worth its weight in gold. Did I mention that it’s available in RES Workspace Manager too? Winking smile

Issue #4

Finding out when and by whom the changes were made. Whether they be changes made to the gold image or Ad-Hoc emergency it doesn’t matter the audit trail of the changes is vitally important especially with change management processes. Well would be surprised to hear that RES Automation Manager has an in-built Audit Trail which allows you to view all actions performed in RES Automation Manager – how handy is that when a witch hunt is on (Oh that never happens now does it!?).

Issue #5

As usual I’ve saved the best until last and you didn’t see number 5 coming! The “pièce de résistance” if you like. This might get a bit confusing so strap yourselves in ready…

Emergency changes to running PVS instances are pain. Depending on your configuration after a reboot changes may be lost and depending on your requirements, you may reboot nightly or even weekly. If there is a configuration change that needs to be made then ultimately we need to update the master image. We can implement the change on the running instances, but it will be lost at some point when the write cache is cleared. Until the master image is updated we will need to implement the change, potentially after every reboot.

Because RES Automation Manager is a Run Book Automation tool we can implement this change across all running instances within minutes. “WAIT!”, I hear you cry, “These changes will be lost after a reboot!” Correct. But now we have achieved two things; documented the change and can automate the update to the master image at some point in the future.

Why did I say at “some point in the future?” Fortunately for us there is a hidden gem within RES Automation Manager called Snapshot Intelligence. With a name like that it better be good right!?

As the RES Automation Manager database has a record of all jobs that have executed on a given agent it can detect a snapshot. Whether this is a virtual snapshot or a backup restoration, it makes no odds. In our PVS world, if RES Automation Manager jobs have been run on a machine and the PVS instance is reset back to our master image state (write cache cleared), RES Automation Manager will detect this as a snapshot. You with me so far..?!

Once a snapshot is detected, RES Automation Manager can automatically reapply the job history (I’ll pause whilst you take this in and wait for the penny to drop!).

So if we automate all the emergency or ad-hoc updates with Automation Manager we can automatically reapply these after every reboot? Yes. No need to update the master image for every change? Yes.

In fact it gets better than that. When we update our master image we can run the exact same job history (automatically if you wish) to update the gold image. If you want to cut a new image from scratch we’ve got that covered too. Above all, if everything is automated with RES Automation Manager it’s automatically documented too. Needless to say, you get all the usual audit logging and change history.

Summary

So, in summary, using RES Automation Manager in combination with Citrix Provisioning Services has huge benefits, but there’s obviously a cost associated. Would I recommend it? Absolutely! For all of the above reasons. Is it worth it? Unfortunately, I can’t tell you that as only you know your environment.

Can RES Automation Manager replace Provisioning Services? Not entirely as you’ll still need WDS/MDT (or equivalent) to deploy the OS. It also depends on your reasons for deploying PVS in the first place. If it’s for near instant deployment, remove local disks, reduce the storage footprint or a clean image on every reboot, you’ll probably be using it for a long while yet. If your reasons are purely for “single image” management then you could potentially replace PVS in favour of a “traditional” deployment. Would I recommend this? It depends!

I know we’ve been focused on Provisioning Services in this article but RES Automation Manager will help you with the rest of your infrastructure automation. Desktops, laptops, servers; Exchange and Active Directory etc. You may have XenDesktop, Quest vWorkspace or VMware View for your virtual desktops. The same principal applies and you may even be using PVS in combination with these. Anyway, I don’t need to preach to the converted!

I will say that it should be a strategic decision to deploy RES Automation Manager. Don’t underestimate the amount of time it takes to automate and test. But I guess you already spend a lot of time testing your images?

You can find some video overviews/introductions on RES Automation Manager on Citrix TV and RES Tutorials. If you don’t want to take the time to download, install and configure RES Automation Manager but want to take a quick look, you can always request access to the RES Showcase. Some background and example videos on the Showcase platform can be also found here.

I’ll get off my soapbox now and crawl back to whence I came! Please feel free to comment and I’d love to hear your thoughts. Iain

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