Archive for the 'Powershell' Category

Suspend Hyper-V VMs with PowerShell

I have one Hyper-V R2 server that fights with me on occasion. The VMs are responsive and I can RDP into them. The server itself is sometimes responsive, and I can RDP into it, but it fails to connect to Hyper-V manager. A reboot usually clears up the problem, but I hate to reboot the host machine with VMs still running.

I have noticed, however, that I can still access Hyper-V through the PowerShell API. As the VMs on this machine aren’t critical, I can suspend the VMs using the API. Then I can reboot the host machine, and start the VMs back up again using Hyper-V manager.

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Disable / Enable NICs via Powershell

A client I was working with was having an issue with their Virtual Machine (VM) running on Hyper-V. It was an odd one that I have never seen before. The VM was running Server 2008 R2 and had a single synthetic Virtual NIC attached with a static IP. The problem was that when the VM was restored from a saved state, occasionally, the network would not work. This obviously caused issues for users that needed to connect to the VM via RDP. Luckily, this VM did not completely rely on the Internet, so minor downtime when the VM was restored from a saved state wasn’t a major issue. Disconnecting and reconnecting the NIC in Hyper-V did not fix the issue, and ipconfig /renew wouldn’t fix anything since the IP address was static. The only thing the admin was able to do to temporarily fix the issue (until the next saved state restore) was to log into the VM via Hyper-V console and disable and then enable the NIC that was having issues. Unfortunately, time was a factor in finding a solution, and I was unable to physically see the hardware or VM in action. This made it very difficult to figure out what was causing the issue in the first place. A workaround seemed to be a much better use of time than spending hours trying to deduce the problem via E-mail.

The restore action for the saved state was done by via script. So it would be very easy to tie in another script to essentially disable and enable the NIC after the VM was restored. From what I can tell, this can’t be done using the Hyper-V Powershell APIs from the host. Also, since the network was the problem, I couldn’t run a remote script from the host to fix the NIC. Anything that could be done would have to be done within the VM. Granted this is not a solution to the original problem, but a workaround, and given more time we would have looked into what the actual cause was. So, here is the workaround to the problem.

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Full Sound Through RDP From a Hyper-V Windows 7 VM

Windows 7 is a nice operating system and it has some pretty cool features. One of which, and one of my favorites, is that it comes with the newest version of Remote Desktop (RDP). This version is capable of letting you watch HD video through it (assuming your network connection is fast enough…). RDPing from one physical computer to another physical computer is easy and sound between the two works just fine. This is because both machines (most likely) have physical sound cards.

Sometime during my travels, I loaded Windows 7 onto a Virtual Machine (VM) running on Hyper-V Server 2008 R2. Virtual Machines in Hyper-V don’t have physical or even virtual sound cards like VPC. When RDPing to a Windows 7 VM the sound card is listed as Remote Audio. This is fine and will actually push through a decent amount of sound. While testing, it seemed to work fine for WMV files and a few other formats. For some reason, I was unable to get it to work with AVI files, and flash websites like I wanted full sound capabilities. So here is what I was able to get working.

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Creating and Executing Powershell Scripts

Writing your first PowerShell script can be pretty easy. Just open notepad and paste in:

Write-Host "Hello World!"

Save that as a .ps1 file and you’re are all set. That line will just print out Hello World! to the console.

Now, how do you run that script?

First, you open up Windows PowerShell. Browse to the location where you script is, and type the name of the script.

If this is your first time running a PowerShell script, chances are you will see an error message like this:

PS C:\Users\user\Desktop> .\HelloWorld.ps1
File C:\Users\user\Desktop\HelloWorld.ps1 cannot be loaded because the execution of scripts is disabled on this system. Please see “get-help about_signing” for more details.
At line:1 char:17
+ .\HelloWorld.ps1 <<<<
+ CategoryInfo : NotSpecified: (:) [], PSSecurityException
+ FullyQualifiedErrorId : RuntimeException

This is because PowerShell is pretty locked down to prevent unauthorized scripts from running.

Chances are you will be fine with:

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