# Azure Platform Customization

Beyond the [platform-agnostic `install-config.yaml` properties](../customization.md#platform-customization), the installer supports additional, Azure-specific properties.

## Cluster-scoped properties

The following options are available when using Azure:

* `region` (required string): The Azure region where the cluster will be created.
* `baseDomainResourceGroupName` (required string): The resource group where the Azure DNS zone for the base domain is found.
* `defaultMachinePlatform` (optional object): Default [Azure-specific machine pool properties](#machine-pools) which applies to [machine pools](../customization.md#machine-pools) that do not define their own Azure-specific properties.
* `networkResourceGroupName` (optional string): The resource group where the Azure VNet is found.
* `virtualNetwork` (optional string): The name of an existing VNet where the cluster infrastructure should be provisioned.
* `controlPlaneSubnet` (optional string): An existing subnet which should be used for the cluster control plane.
* `computeSubnet` (optional string): An existing subnet which should be used by cluster nodes. 

## Machine pools

* `osDisk` (optional object):
    * `diskSizeGB` (optional integer): The size of the disk in gigabytes (GB).
* `type` (optional string): The Azure instance type.
* `zones` (optional string slice): List of Azure availability zones that can be used (for example, `["1", "2", "3"]`).

## Installing to Existing Networks & Subnetworks

The installer can use an existing VNet and subnets when provisioning an OpenShift cluster. If one of `networkResourceGroupName`, `virtualNetwork`, `controlPlaneSubnet`, or `computeSubnet`is specified, all must be specified [(see example below)](#existing-vnet). The installer will use these existing networks when creating infrastructure such as virtual machines, load balancers, and DNS zones.

### Cluster Isolation

When pre-existing subnets are provided, the installer will not create a network security group (NSG) or alter an existing one attached to the subnet. This restriction means that no security rules are created. If multiple clusters are installed to the same VNet and isolation is desired, it must be enforced through an administrative task after the cluster is installed.

## Examples

Some example `install-config.yaml` are shown below.
For examples of platform-agnostic configuration fragments, see [here](../customization.md#examples).

### Minimal

An example minimal Azure install config is:

```yaml
apiVersion: v1
baseDomain: example.com
metadata:
  name: test-cluster
platform:
  azure:
    region: centralus
    baseDomainResourceGroupName: os4-common
pullSecret: '{"auths": ...}'
sshKey: ssh-ed25519 AAAA...
```

### Custom machine pools

An example Azure install config with custom machine pools:

```yaml
apiVersion: v1
baseDomain: example.com
controlPlane:
  name: master
  platform:
    azure:
      type: Standard_DS4_v2
      osDisk:
        diskSizeGB: 512
  replicas: 3
compute:
- name: worker
  platform:
    azure:
      type: Standard_DS4_v2
      osDisk:
        diskSizeGB: 512
      zones:
      - "1"
      - "2"
      - "3"
  replicas: 5
metadata:
  name: test-cluster
platform:
  azure:
    region: centralus
    baseDomainResourceGroupName: os4-common
pullSecret: '{"auths": ...}'
sshKey: ssh-ed25519 AAAA...
```
### Existing VNet

An example Azure install config to use a pre-existing VNet and subnets:

```yaml
apiVersion: v1
baseDomain: example.com
metadata:
  name: test-cluster
platform:
  azure:
    region: centralus
    baseDomainResourceGroupName: os4-common
    networkResourceGroupName: example_vnet_rg
    virtualNetwork: example_vnet
    controlPlaneSubnet: example_master_subnet
    computeSubnet: example_worker_subnet
pullSecret: '{"auths": ...}'
sshKey: ssh-ed25519 AAAA...
```
