Linode

This guide will show you how to provision (Create, Update, Delete) a Linode Instance using Kubeform.

Examples used in this guide can be found here.

At first, let’s look at the Terraform configuration for a Linode Instance below:

provider "linode" {
    token = "LINODE_API_TOKEN"
}

resource "linode_instance" "test1" {
    image = "linode/ubuntu18.04"

    label = "instance-test1"

    region = "us-east"

    root_pass = "[email protected]"
}

Now, if we apply terraform apply this config will create a Linode Instance. We’ll create the exact configuration using Kubeform. The steps are given below:

1. Before You Begin

At first, you need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. If you do not already have a cluster, you can create one by using kind.

Now, install Kubeform Linode provider operator in your cluster following the steps here. To get a FREE license, please visit here.

helm install kubeform-provider-linode appscode/kubeform-provider-linode \
  --namespace kubeform --create-namespace \
  --set-file kubeform-provider.license=/path/to/the/license.txt \
  --set crds.instance=true

To keep things isolated, this tutorial uses a separate namespace called demo throughout this tutorial.

$ kubectl create ns demo
namespace/demo created

2. Create Linode Provider Secret

Then create the secret which is necessary for provisioning the Instance in Linode.

apiVersion: v1
kind: Secret
metadata:
  name: linode-provider-secret
  namespace: demo
stringData:
  provider: |
    {
        "token": "LINODE_API_TOKEN"
    }    

Here we can see that, the provider field of the stringData of the secret is same as the field of the provider part in the terraform config file. The provider secret needs to be provided in json format, under the provider key. Save it in a file (eg. provider-secret.yaml) then apply it using kubectl command.

kubectl apply -f provider-secret.yaml

Note: Here, key of the provider field of the stringData (eg. "token") must be in snake case format (same as the tf configuration file)

3. Create Secrets for Sensitive Data

If we look at the terraform config, we can see that there is a field called root_pass. This is a sensitive field. So, we should not use these kinds of sensitive values directly in the yaml. We’ll create a secret to store the sensitive values like this:

apiVersion: v1
kind: Secret
metadata:
  name: linode-sensitive-secret
  namespace: demo
stringData:
  input: |
    {
        "root_pass": "[email protected]"
    }    

Here, sensitive secret needs to be provided in json format, under the input key. We’ll reference this secret from the Instance CRD. Save it in a file (eg. sensitive-secret.yaml) then apply it using kubectl command.

kubectl apply -f sensitive-secret.yaml

Note: Here, key of input field of the stringData (eg. "root_pass") must be in snake case format (same as the tf configuration file)

4. Create Instance

Now, we’ll create the Instance CRD. The yaml is given below:

apiVersion: instance.linode.kubeform.com/v1alpha1
kind: Instance
metadata:
  name: test1
  namespace: demo
spec:
  resource:
    region: us-east
    image: linode/ubuntu18.04
    label: instance-test1
  providerRef:
    name: linode-provider-secret
  secretRef:
    name: linode-sensitive-secret
  terminationPolicy: DoNotTerminate

Here, the resource field contains the Linode Instance spec. Also, we can see that the provider secret is referenced using a field called providerRef and the sensitive value secret is referenced using a field called secretRef.

We can see a field named terminationPolicy, this is a feature of Kubeform. This field can have two values, Delete or DoNotTerminate. When the value of this field is set to DoNotTerminate then the Instance won’t get deleted even though we apply kubectl delete operation, this field needs to be set to Delete to delete the Instance. It helps to avoid accidental deletion of the resource. We will see the use of this field in Delete Instance part later on this guide.

Save it in a file (eg. linode-instance.yaml) then apply it using kubectl.

kubectl apply -f linode-instance.yaml

After applying this command, the resource will be in InProgress phase until the cloud creates the resource. Once the cloud resource get created, the resource will be in Current phase which means we have successfully created the resource.

After successful creation of the resource, the resource state is available under spec.state section. This spec.state field maps the real world resource to the Kubeform resource. This field doesn’t contain any sensitive field. Sensitive fields are stored in the secret specified in the spec.secretRef section. If no secretRef is specified, Kubeform will create one.

5. Update Instance

Now, we’ll update the Instance CRD. For updating the Instance, we will modify the existing linode-instnace.yaml, we will use a different label (instance-test1-update). The modified yaml is given below:

apiVersion: instance.linode.kubeform.com/v1alpha1
kind: Instance
metadata:
  name: test1
  namespace: demo
spec:
  resource:
    region: us-east
    image: linode/ubuntu18.04
    label: instance-test1-update
  providerRef:
    name: linode-provider-secret
  secretRef:
    name: linode-sensitive-secret
  terminationPolicy: DoNotTerminate

Now, apply it using kubectl command.

kubectl apply -f linode-instance.yaml

After that, existing Linode Instance will be updated!

Note: Here, we have changed the label field which is mutable, means if we change a mutable field it will get updated/changed only. But, there are some fields which are immutable, means changing those fields, resource will first get deleted and then again recreated. So, be careful!

6. Delete Instance

To delete the Instance just run:

kubectl delete -f linode-instance.yaml

After applying this command we will get below error message, as we have set terminationPolicy: DoNotTerminate:

Error from server (instance "default/test1" can't be terminated. To delete, change spec.terminationPolicy to Delete): error when deleting "linode-instance.yaml": admission webhook "instance.instance.linode.kubeform.com" denied the request: instance "default/test1" can't be terminated. To delete, change spec.terminationPolicy to Delete

Let’s change the terminationPolicy to Delete by using kubectl patch command.

kubectl patch -n demo instance test1 -p '{"spec":{"terminationPolicy":"Delete"}}' --type="merge"

Now, we can delete the Instance.

kubectl delete -f linode-instance.yaml

After applying this command the resource will be in Terminating phase until the cloud resource get destroyed. Once the cloud resource get destroyed, the resource will get deleted successfully.