Use existing VHD for AzureRM VM

Q. How do I use an existing VHD when creating a VM using AzureRM?

A. Normally when creating a new VM you have code to set a credential, set an OS type and select a base image. For example:

$osDiskName = $vmname+'_osDisk'
$osDiskCaching = 'ReadWrite'
$osDiskVhdUri = "https://$stoname.blob.core.windows.net/vhds/"+$vmname+"_os.vhd"

# Setup OS & Image
$user = "localadmin"
$password = 'Pa55word5'
$securePassword = ConvertTo-SecureString $password -AsPlainText -Force
$cred = New-Object System.Management.Automation.PSCredential ($user, $securePassword) 
$vm = Set-AzureRmVMOperatingSystem -VM $vm -Windows -ComputerName $vmname -Credential $cred
$vm = Set-AzureRmVMSourceImage -VM $vm -PublisherName $AzureImage.PublisherName -Offer $AzureImage.Offer `
    -Skus $AzureImage.Skus -Version $AzureImage.Version
$vm = Set-AzureRmVMOSDisk -VM $vm -VhdUri $osDiskVhdUri -name $osDiskName -CreateOption fromImage -Caching $osDiskCaching

To use an existing disk replace all of the above with:

$osDiskName = $vmname+'_osDisk'
$osDiskCaching = 'ReadWrite'
$osDiskVhdUri = "https://$stoname.blob.core.windows.net/vhds/"+$vmname+"_os.vhd"

$vm = Set-AzureRmVMOSDisk -VM $vm -VhdUri $osDiskVhdUri -name $osDiskName -CreateOption attach -Windows -Caching $osDiskCaching

Note you still set variables for the disk name, caching and location but the attach create option is used instead of fromImage.