Launching VMs from images and capturing images from VMs with the Azure REST API (C#)

Windows Azure's REST API is a web service which you can use to interact with your Azure subscription.

To use it, you first need to create and a certificate to access your subscription with the API. Microsoft describe the process quite well here: http://msdn.microsoft.com/en-us/library/windowsazure/gg551722.aspx

Once you have created your certificate and uploaded it on the Azure portal, you can use the code provided by Microsoft to use your new certificate in your C# project: http://msdn.microsoft.com/en-us/library/windowsazure/ee460782.aspx

A general method to call REST API XML

All requests can be generated through this code. You pass through the XML, the request URL, and request type. This request object stores a request ID which can be used to check the request status.

Creating a cloud service

Before launching a VM from an image, you need to create a cloud service for it. You need to have a cloud service for each image created.

Request URL: https://management.core.windows.net/[subscription-id]/services/hostedservices
Request type: POST
Return the XML required with the following method:

Launching a VM from an image

Once you have manually created an image on the Azure portal, you can launch it from the REST API as follows:

Request URL: https://management.core.windows.net/[subscription-id]/services/hostedservices/[service-name]/deployments
You need to use the service name of the service you just created.
Request type: POST
Return the XML with the following method:

Capturing an image from a VM

When you have finished working on the VM, it is important that the VM runs Sysprep.exe and shuts itself down. This can be done in a batch file with the following command:

When the VM is shut down, you can call the following code to capture an image: (Note that you can't overwrite images - you need to delete the old one first if you want the image to have the same name)

Request URL: https://management.core.windows.net/[subscription-id]/services/hostedservices/[service-name]/deployments/[deployment-name]/roleinstances/[vm-name]/operations

You need to use the service name, deployment name and machine name configured earlier.

Request type: POST
Return the XML with the following method:

Deleting and discarding your VM

Request URL: https://management.core.windows.net/[subscription-id]/services/hostedservices/[service-name]/deployments/[vm-name]

You need to use the names of the service and virtual machines created earlier.
Request type: DELETE
No request XML required.

Deleting your cloud service

Request URL: https://management.core.windows.net/[subscription-id]/services/hostedservices/[service-name]

You need to use the service name of the service you just created.
Request type: DELETE
No request XML required.

Checking the result of a REST API call

The REST API provides a way to check the result of your call. The first block of code described in this post includes a method MakeStatusRequest, which returns a 0 if a "successful" result is returned by Azure. Provide it with the URL https://management.core.windows.net/[subscription-id]/operations/[request-id]  (where request-id is the requestID of the request you passed earlier)

It is useful to put this in a loop which checks for a successful result, and returns failure upon timeout. I call it as such: