Convert Azure Windows virtual machine license to Hybrid Use Benefit

EDIT: This functionality is now directly in the portal. Just select the VM, click configuration and you should now see the ability to switch license type.

Microsoft has recently announced their hybrid use benefit for Windows virtual machines. They claim a 40% lower price on Windows VMs in Azure which is certainly a good thing.

If you license your on premises hosts with Windows Datacentre and also run some Azure Windows VMs then you can use the license for both - at the same time!

"Each two-processor licence or each set of 16-core licences are entitled to two instances of up to 8 cores, or one instance of up to 16 cores. The Azure Hybrid Use Benefit for Standard Edition licences can only be used once either on-premises or in Azure. Datacenter edition benefits allow for simultaneous usage both on-premises and in Azure."

The only issue with this offer is that you need to enable the hybrid use at deploy time on your VMs. This isn't a problem for ephemeral VMs, but if you have permanent VMs that you want to save some money on, then you need to re-provision them.

It is possible to delete your VMs and then recreate them using the original VHD, with the hybrid use benefit enabled. I've written a script which will do just this and published it on GitHub here.

As always, DO NOT use this in production and make sure you have backups of your machines before you use the script!

Be aware that this will only work on some VMs, I've not yet worked out the prerequisites. The script *should* detect if it hasn't worked and put your VM back with it's original license if the ARM platform throws an error. To put this in perspective, I've run the script on 8 VMs, 1 of which didn't work.

Update: Should now work with managed disk VMs