Remotely Brick a System

I have another fun project. After some recent system performance analyses, one of my recommendations was to move appropriate systems to VMware’s Paravirtual SCSI controller. We don’t go the vCAC/vRA route yet, so I’m now tasked with integrating this into our fun little ASP.NET/C#, PowerShell, MDT, and SQL deployment Frankenstein. It may be ugly, but it was a fantastic learning experience, and works quite well.

When designing tooling, I usually step through what I want to do manually, and break each step up as needed, building re-usable tools where appropriate. Here’s the recipe, ignoring a paranoid level of error handling:

  • Check to see which of the guest’s disks are online (Why?  We’ll see…)
  • Power off the guest
  • Change all non-system drives to a new Paravirtual SCSI controller
  • Power on the guest
  • All your disks are gone!
  • Set your disks that are offline back to online. Each test case of mine resulted in all migrated disks coming up as offline.
  • See all those ‘Power’ tasks? All this will need to be performed from a remote system.

Most of this is vanilla PowerCLI. A few steps require something like DiskPart though. Yes, Windows 6.2 and later include Storage Cmdlets. Unfortunately, Microsoft cut off legacy systems, along with the many organizations out there who still rely on them, even if they can roll out 2012 R2 boxes for new projects. DiskPart it is!

Tangent: Whomever decided to include OS-specific-Cmdlets in certain DSC Resources made me sad. The whole OS-specific-Cmdlet idea has lead to a good deal of confusion, and relying on it in a technology that’s slated for inclusion in the Common Engineering Criteria (presumably as the standard for configuration management) might not help with adoption.

DiskPart on a remote computer

The blog title should make sense at this point; thankfully, no systems were harmed in the writing of this post. So, we have a set of DiskPart commands that need to run remotely. How do we do it?

A while back I wrote New-RemoteProcess. It was the second PowerShell function I published, definitely not my proudest work, but it does the trick; I have my remoting mechanism. Now I need to parse out online disks to know which offline disks should really be online. I sifted through the numerous PowerShell+DiskPart posts out there and didn’t find much on running it remotely. I did find Alan Conkle’s code for parsing disk, volume, and vdisk output. We tweaked New-RemoteProcess to give us Invoke-DiskPartScript, which we can use inside a few Get-DiskPart* functions that mash in Alan’s code.

The result? You can now remotely brick a system. Or check for offline disks and set them back to online after changing to a Paravirtual controller, your choice!

PSDiskPart

I packaged my functions up into PSDiskPart, and committed them to GitHub. If you need to run Diskpart against a remote system, and remoting + OS-specific-Storage-Cmdlets won’t work for you, give this a shot! If you have any suggestions or tips, pull requests would be appreciated.

Here are a few examples from my environment:

Get disk info for a few computers, pick out a few properties:Get-DiskPartDisk

Get volume information from the current computer:

Get-DiskPartVolume

Set a disk to offline… Don’t do this to a production system : )

Invoke-DiskPartScript-Offline

Bring a disk back online, and remove the readonly flag if it is set:

Invoke-DiskPartScript-Online

Invoke-DiskPartScript and Sleep

I did run into a small issue with the borrowed logic from New-RemoteProcess. Every so often, I simply wouldn’t get results back. Adding start-sleep resolved this, but seemed inefficient.

I wanted something where I could say ‘wait until you can see this file.’ This is simple enough to write, but one of the things I love about PowerShell is that it is task-based. I want to wait for a path to exist, export to a csv, create a VM, or perform some other specific task, not worry about the logic and error handling behind each of these tasks.

I didn’t see anything out there, so I drafted up Wait-Path, which returns more quickly than hard coding a start-sleep call.

Up next

My wife is out of town this week. This means I have more time to play and to wrap up a few posts I have planned. No promises, but the following are on my plate:

  • REST / Infoblox –  A follow-up walking through a few Infoblox functions, illustrating why it would be quite nice if vendors provided their own PowerShell modules.
  • Invoke-SqlCmd2 – Highlight some of this function’s features, with some practical examples. Pre-staging a computer and applications in MDT? Getting migrated objects from ADMT? Diving into OpsMgr? Too many choices…
  • Building an inventory database – Not everyone has a mature CMDB. Create a database that can track details on servers, SQL instances, SQL databases, scheduled tasks, and more.
  • Filling an inventory database – Now that we have an inventory database, collect the data! This boils down to the products and attributes you want to track, but we can start with some basics.

Cheers!

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s