This guide is part 2 of a series.

Part 1 covers to installing Crossplane and connect your Kubernetes cluster to Azure.

This guide walks you through building and accessing a custom API with Crossplane.


  • Complete quickstart part 1 connecting Kubernetes to Azure.
  • an Azure account with permissions to create an Azure Virtual Machine, Resource Group and Virtual Networking.

  1. Add the Crossplane Helm repository and install Crossplane
1helm repo add \
3helm repo update
5helm install crossplane \
6crossplane-stable/crossplane \
7--namespace crossplane-system \
  1. When the Crossplane pods finish installing and are ready, apply the Azure Provider
1cat <<EOF | kubectl apply -f -
3kind: Provider
5  name: provider-azure-network
7  package:
  1. Use the Azure CLI to create a service principal and save the JSON output as azure-crednetials.json
1az ad sp create-for-rbac \
2--sdk-auth \
3--role Owner \
4--scopes /subscriptions/
  1. Create a Kubernetes secret from the Azure JSON file.
1kubectl create secret \
2generic azure-secret \
3-n crossplane-system \
  1. Create a ProviderConfig
 1cat <<EOF | kubectl apply -f -
 4  name: default
 5kind: ProviderConfig
 7  credentials:
 8    source: Secret
 9    secretRef:
10      namespace: crossplane-system
11      name: azure-secret
12      key: creds

Create a custom API

Crossplane allows you to build your own custom APIs for your users, abstracting away details about the cloud provider and their resources. You can make your API as complex or simple as you wish.

The custom API is a Kubernetes object.
Here is an example custom API.

2kind: VirtualMachine
4  name: my-vm
6  location: "US"

Like any Kubernetes object the API has a version, kind and spec.

Define a group and version

To create your own API start by defining an API group and version.

The group can be any value, but common convention is to map to a fully qualified domain name.

The version shows how mature or stable the API is and increments when changing, adding or removing fields in the API.

Crossplane doesn’t require specific versions or a specific version naming convention, but following Kubernetes API versioning guidelines is strongly recommended.

  • v1alpha1 - A new API that may change at any time.
  • v1beta1 - An existing API that’s considered stable. Breaking changes are strongly discouraged.
  • v1 - A stable API that doesn’t have breaking changes.

This guide uses the group

Because this is the first version of the API, this guide uses the version v1alpha1.


Define a kind

The API group is a logical collection of related APIs. In a group are individual kinds representing different resources.

For example a compute group may have a VirtualMachine and BareMetal kinds.

The kind can be anything, but it must be UpperCamelCased.

This API’s kind is VirtualMachine

2kind: VirtualMachine

Define a spec

The most important part of an API is the schema. The schema defines the inputs accepted from users.

This API allows users to provide a location of where to run their cloud resources.

All other resource settings can’t be configurable by the users. This allows Crossplane to enforce any policies and standards without worrying about user errors.

2kind: VirtualMachine
4  location: "US"

Apply the API

Crossplane uses Composite Resource Definitions (also called an XRD) to install your custom API in Kubernetes.

The XRD spec contains all the information about the API including the group, version, kind and schema.

The XRD’s name must be the combination of the plural and group.

The schema uses the OpenAPIv3 specification to define the API spec.

The API defines a location that must be oneOf either EU or US.

Apply this XRD to create the custom API in your Kubernetes cluster.

 1cat <<EOF | kubectl apply -f -
 3kind: CompositeResourceDefinition
 5  name:
 7  group:
 8  names:
 9    kind: VirtualMachine
10    plural: virtualmachines
11  versions:
12  - name: v1alpha1
13    schema:
14      openAPIV3Schema:
15        type: object
16        properties:
17          spec:
18            type: object
19            properties:
20              location:
21                type: string
22                oneOf:
23                  - pattern: '^EU$'
24                  - pattern: '^US$'
25            required:
26              - location
27    served: true
28    referenceable: true
29  claimNames:
30    kind: VirtualMachineClaim
31    plural: virtualmachineclaims

Adding the claimNames allows users to access this API either at the cluster level with the VirtualMachine endpoint or in a namespace with the VirtualMachineClaim endpoint.

The namespace scoped API is a Crossplane Claim.

For more details on the fields and options of Composite Resource Definitions read the XRD documentation.

View the installed XRD with kubectl get xrd.

1kubectl get xrd
2NAME                                  ESTABLISHED   OFFERED   AGE   True          True      43s

View the new custom API endpoints with kubectl api-resources | grep VirtualMachine

1kubectl api-resources | grep VirtualMachine
2virtualmachineclaims               true         VirtualMachineClaim
3virtualmachines                    false        VirtualMachine

Create a deployment template

When users access the custom API Crossplane takes their inputs and combines them with a template describing what infrastructure to deploy. Crossplane calls this template a Composition.

The Composition defines all the cloud resources to deploy. Each entry in the template is a full resource definitions, defining all the resource settings and metadata like labels and annotations.

This template creates an Azure LinuxVirtualMachine NetworkInterface, Subnet VirtualNetwork and ResourceGroup.

Crossplane uses patches to apply the user’s input to the resource template.
This Composition takes the user’s location input and uses it as the location used in the individual resource.

Apply this Composition to your cluster.

  1cat <<EOF | kubectl apply -f -
  3kind: Composition
  5  name: crossplane-quickstart-vm-with-network
  7  resources:
  8    - name: quickstart-vm
  9      base:
 10        apiVersion:
 11        kind: LinuxVirtualMachine
 12        spec:
 13          forProvider:
 14            adminUsername: adminuser
 15            adminSshKey:
 16              - publicKey: ssh-rsa
 17                  AAAAB3NzaC1yc2EAAAADAQABAAABAQC+wWK73dCr+jgQOAxNsHAnNNNMEMWOHYEccp6wJm2gotpr9katuF/ZAdou5AaW1C61slRkHRkpRRX9FA9CYBiitZgvCCz+3nWNN7l/Up54Zps/pHWGZLHNJZRYyAB6j5yVLMVHIHriY49d/GZTZVNB8GoJv9Gakwc/fuEZYYl4YDFiGMBP///TzlI4jhiJzjKnEvqPFki5p2ZRJqcbCiF4pJrxUQR/RXqVFQdbRLZgYfJ8xGB878RENq3yQ39d8dVOkq4edbkzwcUmwwwkYVPIoDGsYLaRHnG+To7FvMeyO7xDVQkMKzopTQV8AuKpyvpqu0a9pWOMaiCyDytO7GGN
 19                username: adminuser
 20            location: "Central US"
 21            osDisk:
 22              - caching: ReadWrite
 23                storageAccountType: Standard_LRS
 24            resourceGroupNameSelector:
 25              matchControllerRef: true
 26            size: Standard_B1ms
 27            sourceImageReference:
 28              - offer: debian-11
 29                publisher: Debian
 30                sku: 11-backports-gen2
 31                version: latest
 32            networkInterfaceIdsSelector:
 33              matchControllerRef: true
 34      patches:
 35        - type: FromCompositeFieldPath
 36          fromFieldPath: "spec.location"
 37          toFieldPath: "spec.forProvider.location"
 38          transforms:
 39            - type: map
 40              map: 
 41                EU: "Sweden Central"
 42                US: "Central US"
 43    - name: quickstart-nic
 44      base:
 45        apiVersion:
 46        kind: NetworkInterface
 47        spec:
 48          forProvider:
 49            ipConfiguration:
 50              - name: crossplane-quickstart-configuration
 51                privateIpAddressAllocation: Dynamic
 52                subnetIdSelector:
 53                  matchControllerRef: true
 54            location: "Central US"
 55            resourceGroupNameSelector:
 56              matchControllerRef: true
 57      patches:
 58        - type: FromCompositeFieldPath
 59          fromFieldPath: "spec.location"
 60          toFieldPath: "spec.forProvider.location"
 61          transforms:
 62            - type: map
 63              map: 
 64                EU: "Sweden Central"
 65                US: "Central US"            
 66    - name: quickstart-subnet
 67      base:
 68        apiVersion:
 69        kind: Subnet
 70        spec:
 71          forProvider:
 72            addressPrefixes:
 73              -
 74            virtualNetworkNameSelector:
 75              matchControllerRef: true
 76            resourceGroupNameSelector:
 77              matchControllerRef: true
 78      patches:
 79        - type: FromCompositeFieldPath
 80          fromFieldPath: "spec.location"
 81          toFieldPath: "spec.forProvider.location"
 82          transforms:
 83            - type: map
 84              map: 
 85                EU: "Sweden Central"
 86                US: "Central US"
 87    - name: quickstart-network
 88      base:
 89        apiVersion:
 90        kind: VirtualNetwork
 91        spec:
 92          forProvider:
 93            addressSpace:
 94              -
 95            location: "Central US"
 96            resourceGroupNameSelector:
 97              matchControllerRef: true
 98      patches:
 99        - type: FromCompositeFieldPath
100          fromFieldPath: "spec.location"
101          toFieldPath: "spec.forProvider.location"
102          transforms:
103            - type: map
104              map: 
105                EU: "Sweden Central"
106                US: "Central US"
107    - name: crossplane-resourcegroup
108      base:
109        apiVersion:
110        kind: ResourceGroup
111        spec:
112          forProvider:
113            location: Central US
114      patches:
115        - type: FromCompositeFieldPath
116          fromFieldPath: "spec.location"
117          toFieldPath: "spec.forProvider.location"
118          transforms:
119            - type: map
120              map: 
121                EU: "Sweden Central"
122                US: "Central US"
123  compositeTypeRef:
124    apiVersion:
125    kind: VirtualMachine

The compositeTypeRef defines which custom APIs can use this template to create resources.


Read the Composition documentation for more information on configuring Compositions and all the available options.

Read the Patch and Transform documentation for more information on how Crossplane uses patches to map user inputs to Composition resource templates.

View the Composition with kubectl get composition

1kubectl get composition
2NAME                                    XR-KIND           XR-APIVERSION                     AGE
3crossplane-quickstart-vm-with-network   XVirtualMachine   77s

Install the Azure virtual machine provider

Part 1 only installed the Azure Virtual Network Provider. To deploying virtual machines requires the Azure Compute provider as well.

Add the new Provider to the cluster.

1cat <<EOF | kubectl apply -f -
3kind: Provider
5  name: provider-azure-compute
7  package:

View the new Compute provider with kubectl get providers.

1kubectl get providers
2NAME                            INSTALLED   HEALTHY   PACKAGE                                                  AGE
3provider-azure-compute          True        True   25s
4provider-azure-network          True        True   3h
5upbound-provider-family-azure   True        True    3h

Access the custom API

With the custom API (XRD) installed and associated to a resource template (Composition) users can access the API to create resources.

Create a VirtualMachine object to create the cloud resources.

1cat <<EOF | kubectl apply -f -
3kind: VirtualMachine
5  name: my-vm
7  location: "EU"

View the resource with kubectl get VirtualMachine.

It may take up to five minutes for the resources to provision.
1kubectl get VirtualMachine
2NAME    SYNCED   READY   COMPOSITION                             AGE
3my-vm   True     True    crossplane-quickstart-vm-with-network   3m3s

This object is a Crossplane composite resource (also called an XR).
It’s a single object representing the collection of resources created from the Composition template.

View the individual resources with kubectl get managed

 1kubectl get managed
 2NAME                                         READY   SYNCED   EXTERNAL-NAME   AGE   True    True     my-vm-7jb4n     3m43s
 5NAME                                                       READY   SYNCED   EXTERNAL-NAME   AGE   True    True     my-vm-5h7p4     3m43s
 8NAME                                                    READY   SYNCED   EXTERNAL-NAME   AGE   True    True     my-vm-j7fpx     3m43s
11NAME                                          READY   SYNCED   EXTERNAL-NAME   AGE   True    True     my-vm-b2dqt     3m43s
14NAME                                                  READY   SYNCED   EXTERNAL-NAME   AGE   True    True     my-vm-pd2sw     3m43s

Accessing the API created all five resources defined in the template and linked them together.

Look at a specific resource to see it’s created in the location used in the API.

1kubectl describe linuxvirtualmachine | grep Location
2    Location:                         Sweden Central
3    Location:                         swedencentral

Delete the resources with kubectl delete VirtualMachine.

1kubectl delete VirtualMachine my-vm "my-vm" deleted

Verify Crossplane deleted the resources with kubectl get managed

It may take up to 5 minutes to delete the resources.
1kubectl get managed
2No resources found

Using the API with namespaces

Accessing the API VirtualMachine happens at the cluster scope.
Most organizations isolate their users into namespaces.

A Crossplane Claim is the custom API in a namespace.

Creating a Claim is just like accessing the custom API endpoint, but with the kind from the custom API’s claimNames.

Create a new namespace to test create a Claim in.

1kubectl create namespace crossplane-test

Then create a Claim in the crossplane-test namespace.

1cat <<EOF | kubectl apply -f -
3kind: VirtualMachineClaim
5  name: my-namespaced-vm
6  namespace: crossplane-test
8  location: "EU"

View the Claim with kubectl get claim -n crossplane-test.

1kubectl get claim -n crossplane-test
3my-namespaced-vm   True     True                        5m11s

The Claim automatically creates a composite resource, which creates the managed resources.

View the Crossplane created composite resource with kubectl get composite.

1kubectl get composite
2NAME                     SYNCED   READY   COMPOSITION                             AGE
3my-namespaced-vm-r7gdr   True     True    crossplane-quickstart-vm-with-network   5m33s

Again, view the managed resources with kubectl get managed.

 1NAME                                                          READY   SYNCED   EXTERNAL-NAME                  AGE   True    True     my-namespaced-vm-r7gdr-cvzw6   5m51s
 4NAME                                                                        READY   SYNCED   EXTERNAL-NAME                  AGE   True    True     my-namespaced-vm-r7gdr-vrbgb   5m51s
 7NAME                                                                     READY   SYNCED   EXTERNAL-NAME                  AGE   True    True     my-namespaced-vm-r7gdr-hwrb8   5m51s
10NAME                                                           READY   SYNCED   EXTERNAL-NAME                  AGE   True    True     my-namespaced-vm-r7gdr-gh468   5m51s
13NAME                                                                   READY   SYNCED   EXTERNAL-NAME                  AGE   True    True     my-namespaced-vm-r7gdr-5qhz7   5m51s

Deleting the Claim deletes all the Crossplane generated resources.

kubectl delete claim -n crossplane-test my-VirtualMachine-database

1kubectl delete claim -n crossplane-test my-namespaced-vm "my-namespaced-vm" deleted
It may take up to 5 minutes to delete the resources.

Verify Crossplane deleted the composite resource with kubectl get composite.

1kubectl get composite
2No resources found

Verify Crossplane deleted the managed resources with kubectl get managed.

1kubectl get managed
2No resources found

Next steps