Provisioning a VM from a Snapshot

There are two ways to provision a VM. One is to attach an existing VHD. The other, and more likely approach, is to copy a VM image. Below is a step by step guide to the second approach using The azure-armrest gem.

require 'azure-armest' # This library
require 'securerandom' # In the Ruby stdlib

First, you must know where the image is that you want to copy. The StorageAccountService class may help you here for dynamic lookup.

src_uri = "https://somestorage123.blob.core.windows.net/system/Microsoft.Compute/Images/some-container/dan-img-osDisk.714a9ffb-55c8-4e31-951f-d26307b5afa4.vhd"

Second, you must provide a target location. This is a storage account URI, followed by a container name, followed by the name of the image you want to create. We follow MS practices here and add a GUID to the image name to ensure uniqueness.

We also recommend that you use a common, easily recognizable container name for storing all of your custom provisioning.

vhd_uri = "http://somestorage123.blob.core.windows.net/your_company/testprov1_" + SecureRandom.uuid + ".vhd"

One thing you must have first is a NIC that you will attach to the VM. You can either create a new one or use an existing one. For this example, we'll just use an existing one. While we're at it, we'll also need a VirtualMachineService instance.

vms = Azure::Armrest::VirtualMachineService.new(conf)
nis = Azure::Armrest::Network::NetworkInterfaceService.new(conf)

nic = nis.get('some_nic', 'your_group')

With that set, we need to set our options. For all available options, please see the online REST documentation for Azure. Here we provide enough to at least give you a general idea how things should work.

options = 
{
  :name => 'testprov1',
  :location => 'centralus',
  :properties => {
    :hardwareProfile => { :vmSize => 'Standard_A0' },
    :osProfile => {
      :adminUserName => 'your_username',
      :adminPassword => 'your_password',
      :computerName  => 'whatever_you_want'
    },
    :storageProfile => {
      :osDisk => {
        :createOption => 'FromImage',
        :caching      => 'ReadWrite',
        :name         => 'whatever_' + SecureRandom.uuid + '.vhd',
        :osType       => 'Windows',
        :image        => { :uri => src_uri }, # source
        :vhd          => { :uri => vhd_uri }  # target
      }
    },
    :networkProfile => {
      :networkInterfaces => [{:id => nic.id}]
    }
  }
}

vm.create('testprov1', 'your_group', options)

The name and location are mandatory, as is the information under :osProfile, and the :networkProfile. Here we used the NIC that we retrieved earlier. As a best practice, the :name should match the first part of the target VHD name so that it's easy to identify which VM is associated with which VHD.

The possibilities for the :vmSize option under :hardwareProfile can be found using the VirtualMachineService#series method. Or, you can just lookup the information online to find out what is currently available from MS. Here we use 'Standard_A0', which is the smallest configuration possible.

Under the :osDisk parameter, the :createOption of "FromImage" let's Azure know that you're creating a VM from an image. If you were attaching an existing VHD to a VM, you would use "Attach" here instead (and other options would be different). The :image option is the source image, and the :vhd option is the target image that will be generated.

Note that, at the time of this writing, the :osType can only be "Windows" or "Linux". Hopefully you know the OS type in advance, but if you don't, it can be determined dynamically. See below.

Dynamically Determine the OS Type of an Image

blob_properties.x_ms_meta_microsoftazurecompute_ostype