MonthMarch 2013

Hyper-V Getting MAC Address using VM Name

As part of my automated provisioning (yes – System Center and Sysprep will probably be a better option, but hey whatever) script, I need to be able to automatically assign an IP address to a VM. At this point, the only way I can see this being a possibility is to mount the VHD before booting then copying a script that will set the correct IP address to an autostart location.

The ‘script’ is broken down into two parts. The first needs to run on the node, and create the second script inside the VHD. The second script then needs to identify what network adapter/s are present and assign the correct IP address to each.

The first challenge is finding out how to have the second script identify the correct adapter. I initially though about testing connectivity after the IP address was set, and upon a failure, revert the changes and try the next adapter present. Rather than doing this, I found you can get the MAC address for a VM from the Hyper-V node, and filter based on which Virtual Switch the interface is attached to:

The following example will get the MAC address for a VM based on the VM name, and the network it is attached to:

This returns a MAC address.

I believe I can then use this MAC address in the second part of the script to pull the network adapter name.

Something along the lines of this:

Once I have the correct adapter name, I can use this in an IP address setting script to set the correct IP / gateway etc essentially automating the networking side of provisioning.

At this point there are a few things I have yet to confirm that might make the above attempt futile. First, I do not know if I can run a powershell script on startup – I know there are issues with signed code etc, and this might mean a freshly provisioned system will not allow unsigned code to run – especially if it needs administrator permissions. Second – I don’t know how this will work with a sysprepped image. It is possible (probable?) that with a sysprep image, the network configuration information could be copied to the sysprep config eliminating the need for an autorun script.

You can see an example of a powershell script to assign IP addresses here:

Copy to mounted VHD with PowerShell for automated Hyper-V Provisioning – Part II

While I initially tried to get the Powershell Mount-VHD cmdlet working – I gave up as it didn’t seem to exist (despite obvious documentation:

I was using a Server 2012 DS for testing purposes, but as I was just working on the drive letter side of things – I had yet to install the Hyper-V role. Turns out that Mount-VHD is exactly what I need to get the driveletter of a VHD and requires Hyper-V to be installed. The last example on the Microsoft Site gives you all you need to know:

With a little modification we can ensure that the System Reserved partition does not get in the way:

This is what you will get after mounting using the above command:


You can then select the driveletter column to get what you need:

Much more simple than my previous attempt!


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