All language subtitles for 1. Modify an ARM Template

Now, let's look at how we can modify an

ARM template from an existing resource.

Now, the level of understanding for ARM

templates will not be at the architect or

developer level, thank god. Our main focus

for the 104 exam is to be able to support,

manage or modify ARM templates, nothing

from scratch. You will need to be able to

recognize the code and what it's doing,

more or less. First, we need to get some

of the first principles out of the way as

it relates to ARM templates. Now, they are

in JSON format, JavaScript Object

Notation. Now an ARM template, simply put,

is a JSON object of key value pairs. Now,

we can create any resource in Azure with

an ARM template, then we can submit that

template to the Azure Resource Manager,

ARM, for the deployment, and it helps us

keep track of our deployments as well.

Here's the basic ARM template format. As

we see, we have a number of key value

pairs starting with the schema. Not all of

these pairs are required. In fact, only

schema, contentVersion, and resources are

required. Now, the schema defines the

location of the JSON file that describes

the version of the language. Note the date

in the path. I wouldn't worry too much

about content version. This is related to

the different iterations of this file.

What we're really going to look at is

resources. This is where we define the

resources within Azure we are going to

deploy or update. Yes, I said update. ARM

templates can be used against existing

resources, not just creating new. Note the

square brackets. This signifies this can

be an array of values, which makes sense.

Now the curly brackets are singular

values. In the next few slides, we'll

break down the sections of a template for

a network security group. In this first

slide, we see the schema. As stated, this

is the location of the template file.

Next, we see the parameters. Notice the

default value. This will come into play in

a few slides when we choose the Deploy

option. It will auto populate the name of

the network security group with web‑nsg,

which is the name of the existing security

group we're looking at. So we could modify

the existing group, or we can change the

name when we deploy to create a new

separate network security group. We also

have any variables. This is where we could

really streamline our deployments by

supplying variables rather than hard coded

properties. Again, probably something at a

higher scope than the AZ‑104 exam. Moving

along, we have the meat of the template,

the resources section. Our key value pair

of type has the value of Microsoft.Network

provider with the resource of

networkSecurityGroups. We can see it takes

the name from the parameters section we

identified earlier. We have the location

of this resource, as well as tags. Then we

see the properties of the security rule.

Here we could make any changes or

additions when we choose to deploy.

Perhaps we want to allow port 80, regular

web traffic, in the security rules under

properties. And then we have the

Microsoft.Network provider with the

securityRules resource and its

dependencies, which is the aforementioned

security group. So, as we learn, we can

modify a template in the portal. Now we

have a couple different options. We can go

to the existing resource and choose Export

template under the Automation section.

Then we would select Deploy, and then

choose to edit the template. We could also

download the template and make changes and

then copy/paste them back into that

template. Once the changes are made, we

would then save it and then select

Purchase, as we'll see in the next slide.

This is the screen we will see when we

choose to deploy. We can now edit this

template here, as well as the parameters.

If we're updating, we don't need to change

the name, but if we want a new network

security group, we can change the name

right here; otherwise, any changes will be

applied to the existing network security

group. And then we need to agree to the

terms and conditions and then click

Purchase. What we're agreeing to is that

we are acknowledging what we are deploying

may incur costs, like if you deploy to a

VM, which comes with storage and compute

costs, not so much with a network security

group, though. Then we would click Purchase.