Assigning User Assigned Identity to Azure VMSS fails

Question

I have a VMSS resource linked to a Service Fabric cluster. I have modified the ARM templates to have user managed identity for VMSS.

"variables": {                      
"vmssApiVersion": "2017-03-30",
...
..
}
....
"resources": [
{
"type": "Microsoft.Compute/virtualMachineScaleSets",
"apiVersion": "[variables('vmssApiVersion')]",
"name": "[concat(variables('vmssNamePrefix'),
...
...
"identity": {​​​​​​
    "type": "UserAssigned",
    "identityIds": [
     "/subscriptions/xxxxxxxxxxxxxxxxxxxxxx/resourceGroups/<RG>/providers/Microsoft.ManagedIdentity/userAssignedIdentities/<usrasgid>"       
    ]                     
}​​​​​​
.....
.....
}
]

While deploying, it throws the error

{
    "status": "Failed",
    "error": {
        "code": "InvalidParameter",
        "target": "resourceIdentity.type",
        "message": "ResourceIdentity Type must be provided and set to \"SystemAssigned\"."
    }
}

Why does it ask me to set managed identity to SystemAssigned? How can I set it to user managed identity?

Answer 1

I tested the old versions and seems only SystemAssigned is allowed in API Version 2017-03-30. But , It was successful when I used 2018-06-01. So , as a Solution you can use the below to resolve the issue:

{
    "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
    "contentVersion": "1.0.0.0",
    "resources": [
        {
    "name": "ansumantestvmss",
    "type": "Microsoft.Compute/virtualMachineScaleSets",
    "apiVersion": "2018-06-01",
    "location": "[resourceGroup().location]",
    "identity": {
        "type": "userAssigned",
        "userAssignedIdentities": {
            "[resourceID('Microsoft.ManagedIdentity/userAssignedIdentities/','ansumanmdid')]" : {}
        }
    },
    "properties":{}
}    
]
}

Output: