Azure ARM Template dependsOn: How to reference a VM extension?

Question

I have an Azure ARM Teamplate that should create a Linux VM with Docker. Docker is installed using Azure's DockerExtension. After Docker is installed, I need to run a custom script using Azure's CustomScriptForLinux. Therefore, the second script should depend on the Docker installation. Here is an example that shows how I tried to write that in an ARM template:

{
  ...,
  "variables": {
    "extensionName": "DockerExtension",
    "vmName": "Docker",
    ...
  },
  "resources": [
    ...,
    {
      "type": "Microsoft.Compute/virtualMachines/extensions",
      "name": "[concat(variables('vmName'), '/', variables('extensionName'))]",
      "tags": {
        "displayName": "DockerExtension"
      },
      "apiVersion": "2015-06-15",
      "location": "[resourceGroup().location]",
      "dependsOn": [
        "[concat('Microsoft.Compute/virtualMachines/', variables('vmName'))]"
      ],
      "properties": {
        "publisher": "Microsoft.Azure.Extensions",
        "type": "DockerExtension",
        "typeHandlerVersion": "1.1",
        "autoUpgradeMinorVersion": true,
        "settings": { }
      }
    },
    {
      "type": "Microsoft.Compute/virtualMachines/extensions",
      "name": "[concat(variables('vmName'), '/config')]",
      "apiVersion": "2015-06-15",
      "location": "[resourceGroup().location]",
      "dependsOn": [
        "[concat('Microsoft.Compute/virtualMachines/extensions/', variables('vmName'), '/', variables('extensionName'))]"
      ],
      "properties": {
        "publisher": "Microsoft.OSTCExtensions",
        "type": "CustomScriptForLinux",
        "typeHandlerVersion": "1.4",
        "settings": {
          "fileUris": [
            "..."
          ],
          "commandToExecute": "bash configure.sh"
        }
      }
    }
  ]
}

If I run this ARM template, I get the error The resource 'Microsoft.Compute/virtualMachines/extensions/Docker/DockerExtension' is not defined in the template. I don't understand why. This is the name of the Docker extension I have in my template, isn't it?

The template works if I run just one of the scripts. So there should not be a general error in the template.

Any help appreciated.

Regards, Rainer.

Answer 1

You could try to use the ARM template function resourceId() in your ARM template to reference the Docker extension resource as shown below.

  "type": "Microsoft.Compute/virtualMachines/extensions",
  "name": "[concat(variables('vmName'), '/config')]",
  "dependsOn": [
    "[resourceId('Microsoft.Compute/virtualMachines/extensions', variables('vmName'), variables('extensionName'))]"
  ],...

Reference: Azure Resource Manager template functions

https://azure.microsoft.com/en-gb/documentation/articles/resource-group-template-functions/#resourceid