How to check if resource already exists in the ARM template

Question

I would like to automate the process of ARM deployment in which resource should not get deployed if it already exists.

Trying to implement the below code but getting an error

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "storageAccountName": {
      "type": "string"
    },
    "location": {
      "type": "string",
      "defaultValue": "[resourceGroup().location]"
    },
    "newOrExisting": {
      "type": "string",
      "defaultValue": "new",
      "allowedValues": [
        "new",
        "existing"
      ]
    }
  },
  "resources": {
    "saNew": {
      "condition": "[equals(parameters('newOrExisting'), 'new')]",
      "type": "Microsoft.Storage/storageAccounts",
      "apiVersion": "2022-09-01",
      "name": "[parameters('storageAccountName')]",
      "location": "[parameters('location')]",
      "sku": {
        "name": "Standard_LRS"
      },
      "kind": "StorageV2"
    },
    "saExisting": {
      "condition": "[equals(parameters('newOrExisting'), 'existing')]",
      "existing": true,
      "type": "Microsoft.Storage/storageAccounts",
      "apiVersion": "2022-09-01",
      "name": "[parameters('storageAccountName')]"
    }
  },
  "outputs": {
    "storageAccountId": {
      "type": "string",
      "value": "[if(equals(parameters('newOrExisting'), 'new'), resourceId('Microsoft.Storage/storageAccounts', parameters('storageAccountName')), resourceId('Microsoft.Storage/storageAccounts', parameters('storageAccountName')))]"
    }
  }
}

https://learn.microsoft.com/en-us/azure/azure-resource-manager/templates/conditional-resource-deployment

Answer 1

Hello

I understand that you want to validate whether a resource exists already before deploying an ARM template within the JSON.

ARM Templates cannot do that. You have to find a new method

For the provide code :

In the following ARM template, if the 'newOrExisting' parameter is set to 'new', then the storage account will be created. If it is set to 'existing', the storage account will not be created.

json
{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "storageAccountName": {
      "type": "string"
    },
    "location": {
      "type": "string",
      "defaultValue": "[resourceGroup().location]"
    },
    "newOrExisting": {
      "type": "string",
      "defaultValue": "new",
      "allowedValues": [
        "new",
        "existing"
      ]
    }
  },
  "resources": [
    {
      "condition": "[equals(parameters('newOrExisting'), 'new')]",
      "type": "Microsoft.Storage/storageAccounts",
      "apiVersion": "2022-09-01",
      "name": "[parameters('storageAccountName')]",
      "location": "[parameters('location')]",
      "sku": {
        "name": "Standard_LRS"
      },
      "kind": "StorageV2"
    }
  ],
  "outputs": {
    "storageAccountId": {
      "type": "string",
      "value": "[resourceId('Microsoft.Storage/storageAccounts', parameters('storageAccountName'))]"
    }
  }
}

I hope this helps!

Kindly mark the answer as Accepted and Upvote in case it helped!

Regards