ARM Templates

6 min readFeb 1, 2020

In this section, we will be discussing automation for the deployment of virtual machines. Within MS Azure, automation is usually done using ARM template aka Azure Resource Manager model which is the modern way of deploying resources into azure. The opposite of ARM is ASM aka classic deployment model, which we don’t use any more.

Let’s start this process for the deployment of Virtual Machine. Normally, whenever we deploy any VM, its deployment page appear like this

On the left hand side, you can see you have template section.
When we click on this, it will present the below UI. It consists two files: 1) Templates and 2) Parameter file.

Earlier it used to be CLI, Powershell, .Net, Ruby scripts also. But now only scripts section which look like

Now, I can go ahead and download the template from the download button.
In the downloaded template, I got parameters and template like

Parameters JSON file looks like this.
And template goes like

templates.json file starts with schema as appeared at the top of the file. Then, it also has various parameters in it. This we will eventually use to modify the same.

Variables are similar to parameters; only thing is that these are computed fields.
Key section here is the resources section. This is where all the resources are within this deployment gets defined.
Last section is the output. This ARM template is going to return admin user name as its output.
In case, of parameters, there is going to be one parameter for each of the parameter defined by the template.
The template has one location parameter which is string and in the parameters file, the location is being sent to EastUS.
The way these got these values, how we initially created VM from UI. So, it has grabbed all the values as part of template.

Now, let’s take an example of Network Interface card and explain the same in detail.

It starts with type Microsoft.Network/networkInterfaces. So, this is the network interface resource.
It takes the name of the card from the parameters section.
It has some pretty static code for API version.
The location is the same as we pass in the parameters.
Similarly, we have applied tags.
Network interface card has this IP address which is being setup in the next property under ipconfig.
Down, its giving network security group and nsgId.

And the last thing which I wanted to discuss here is the dependency. It depends on

networkSecurityGroupName
virtualNetworkName
publicIpAddressName

Hence, above listed dependencies need to be created first. Here is the list dependencies

Creating a VM with ARM template is complex task.
In that case, network interface card, its dependencies and then others has to be created first.
So, let’s start with bare minimum changes to start with. Therefore, I will start with network interface card.
I will give it a new name say “rahulnic123″
I am going to keep the same network security group and we will launch in the same virtual network.
However, its going to need the new public ip address, hence say it “azvmdemo2-ip”.
Change the name of VM to “azvmdemo2″.
Leave the other settings as same. So currently, I have modified the parameters file.
Here, azure will consider this template as baseline template as we haven’t changed anything in template and then it can deploy the same template again and again with changed parameters value. This is known as Desired state configuration aka DSC.
Hence, we can take these files, have it in our source control and then we can just do versioning on top of it.
This is also known as Infrastructure as a service.