More Fun with ARM Templates

All this time, all I’ve wanted to do with an Azure Resource Manager (ARM) template was create a bunch of identical computers.   The biggest roadblock I’ve faced is figuring out how to make the ARM template not one gigantic document with similarly-named resources in it.

Each VM requires a public IP address, a NIC, and a VM resource.   When I’ve put those into a template, if I named everything to make sense to me (like “Computer1” would have “Computer1-IP” and “Computer1-NIC” attached to it), the document gets really hard to follow.    I can copy and paste the definitions for these three objects, but eventually it gets ugly and confusing, and when something doesn’t work, it’s a pain to work around.

Enter the “count” parameter!   There’s a neat way that you can tell the ARM engine to iterate through a list of resources and create however many you want it to.   The engine breaks down the JSON file and duplicates the guts of it “n” times, assigning a suffix with the number on it at the end of the item names.

Below is my ARM template that creates as many VMs as you want, each with a public IP address and a NIC.

———————

{
“$schema”: “https://schema.management.azure.com/schemas/2015-01-01/deploymentTemplate.json#”,
“contentVersion”: “1.0.0.0”,
“parameters”: {
“userImageStorageAccountName”: {
“type”: “string”,
“metadata”: {
“description”: “This is the name of the your storage account”
}
},
“userImageStorageContainerName”: {
“type”: “string”,
“metadata”: {
“description”: “This is the name of the container in your storage account”
}
},
“userImageVhdName”: {
“type”: “string”,
“metadata”: {
“description”: “This is the name of the your customized VHD”
}
},
“adminUserName”: {
“type”: “string”,
“metadata”: {
“description”: “UserName for the Virtual Machine”
}
},
“adminPassword”: {
“type”: “securestring”,
“metadata”: {
“description”: “Password for the Virtual Machine”
}
},
“osType”: {
“type”: “string”,
“allowedValues”: [
“windows”,
“linux”
],
“metadata”: {
“description”: “This is the OS that your VM will be running”
}
},
“vmSize”: {
“type”: “string”,
“metadata”: {
“description”: “This is the size of your VM”
}
},
“vmNameBase”: {
“type”: “string”,
“metadata”: {
“description”: “This is the size of your VM”
}
},
“vmCount”:{
“type”: “int”,
“defaultValue”: 1,
“metadata”: {
“description”: “The number of VMs to build.”
}
}
},
“variables”: {
“location”: “[resourceGroup().location]”,
“virtualNetworkName”: “VNetName”,
“addressPrefix”: “10.6.0.0/16”,
“subnet1Name”: “default”,
“subnet1Prefix”: “10.6.0.0/24”,
“publicIPAddressType”: “Dynamic”,
“vnetID”: “[resourceId(‘Microsoft.Network/virtualNetworks’,variables(‘virtualNetworkName’))]”,
“subnet1Ref”: “[concat(variables(‘vnetID’),’/subnets/’,variables(‘subnet1Name’))]”,
“userImageName”: “[concat(‘http://’,parameters(‘userImageStorageAccountName’),’.blob.core.windows.net/’,parameters(‘userImageStorageContainerName’),’/’,parameters(‘userImageVhdName’))]”
},
“resources”: [
{
“apiVersion”: “2015-05-01-preview”,
“type”: “Microsoft.Network/publicIPAddresses”,
“name”: “[concat(parameters(‘vmNameBase’),copyIndex(),’-PublicIP’)]”,
“copy”: {
“name”: “publicIPAddressCopy”,
“count”: “[parameters(‘vmCount’)]”
},
“location”: “[variables(‘location’)]”,
“properties”: {
“publicIPAllocationMethod”: “[variables(‘publicIPAddressType’)]”,
“dnsSettings”: {
“domainNameLabel”: “[concat(parameters(‘vmNameBase’),copyIndex())]”
}
}
},
{
“apiVersion”: “2015-05-01-preview”,
“type”: “Microsoft.Network/networkInterfaces”,
“name”: “[concat(parameters(‘vmNameBase’),copyIndex(),’-NIC’)]”,
“location”: “[variables(‘location’)]”,
“copy”: {
“name”: “networkInterfacesCopy”,
“count”: “[parameters(‘vmCount’)]”
},
“dependsOn”: [
“[concat(‘Microsoft.Network/publicIPAddresses/’, parameters(‘vmNameBase’),copyIndex(),’-PublicIP’)]”
],
“properties”: {
“ipConfigurations”: [
{
“name”: “ipconfig1”,
“properties”: {
“privateIPAllocationMethod”: “Dynamic”,
“publicIPAddress”: {
“id”: “[resourceId(‘Microsoft.Network/publicIPAddresses/’,concat(parameters(‘vmNameBase’),copyIndex(),’-PublicIP’))]”
},
“subnet”: {
“id”: “[variables(‘subnet1Ref’)]”
}
}
}
]
}
},
{
“apiVersion”: “2015-06-15”,
“type”: “Microsoft.Compute/virtualMachines”,
“name”: “[concat(parameters(‘vmNameBase’),copyIndex())]”,
“copy”: {
“name”: “vmCopy”,
“count”: “[parameters(‘vmCount’)]”
},
“location”: “[variables(‘location’)]”,
“dependsOn”: [
“[concat(‘Microsoft.Network/networkInterfaces/’,parameters(‘vmNameBase’),copyIndex(),’-NIC’)]”,
“[concat(‘Microsoft.Network/publicIPAddresses/’, parameters(‘vmNameBase’),copyIndex(),’-PublicIP’)]”
],
“properties”: {
“hardwareProfile”: {
“vmSize”: “[parameters(‘vmSize’)]”
},
“osProfile”: {
“computername”: “[concat(parameters(‘vmNameBase’),copyIndex())]”,
“adminUsername”: “[parameters(‘adminUsername’)]”,
“adminPassword”: “[parameters(‘adminPassword’)]”
},
“storageProfile”: {
“osDisk”: {
“name”: “[concat(parameters(‘vmNameBase’),copyIndex(),’-osDisk’)]”,
“osType”: “[parameters(‘osType’)]”,
“caching”: “ReadWrite”,
“createOption”: “FromImage”,
“image”: {
“uri”: “[variables(‘userImageName’)]”
},
“vhd”: {
“uri”: “[concat(‘http://’,parameters(‘userImageStorageAccountName’),’.blob.core.windows.net/vhds/’,parameters(‘vmNameBase’), copyIndex(),’-osDisk.vhd’)]”
}
}
},
“networkProfile”: {
“name”: “[concat(parameters(‘vmNameBase’),copyIndex(),’-networkProfile’)]”,
“networkInterfaces”: [
{
“id”: “[resourceId(‘Microsoft.Network/networkInterfaces/’,concat(parameters(‘vmNameBase’),copyIndex(),’-NIC’))]”
}
]
},
“diagnosticsProfile”: {

“bootDiagnostics”: {
“enabled”: “true”,
“storageUri”: “[concat(‘http://’,parameters(‘userImageStorageAccountName’),’.blob.core.windows.net’)]”
}
}
}
}
]
}

——————————————————-

The “copyIndex()” command is what tells the ARM engine to use the value from the loop.   Using “DependsOn” with this, means that Computer1 will depend upong Computer1-NIC and Computer1-PublicIP, so nothing will be built if the other parts aren’t ready for it.

This template is setup to be used with a user image, something custom that I’ve put up there that’s already sysprepped and ready-to-go.  I haven’t yet made this add the resources for the extensions or gotten it to join the domain after being built, but at least I have the VMs running now.

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