ImagePullSecrets & Private Registries With Cluster API

Hey guys! Today, we're diving deep into a crucial aspect of Cluster API: how to effectively manage imagePullSecrets, private registries, and separate configuration secrets when you're juggling multiple infrastructure providers. For those of you who are operating Kubernetes clusters in production, this is definitely something you'll want to understand. Let's break it down in a way that's both informative and, dare I say, a little bit fun!

The User Story: Why This Matters

Let's start with the user story. Imagine you're an operator, and you want the ability to define imagePullSecrets and a private image registry for all your provider deployments. Why? Customization, control, and avoiding reliance on public image registries are key! This is about having the flexibility to tailor your deployments to your specific needs and security requirements. In essence, it's about taking charge of your infrastructure. Now, let’s explore how we can achieve this.

Defining ImagePullSecrets and Private Registries for Providers

By default, Cluster API provider manifests are often fetched from upstream repositories. This means that the deployments created typically pull images from public image registries. While this works in many scenarios, it’s not ideal for everyone. Some organizations require the use of private registries for security or compliance reasons. Others might want to use custom images. So, how do we make this happen?

The beauty of Cluster API is its extensibility. Several custom resources support the spec.deployment schema, allowing you to configure custom imageUrl and imagePullSecrets. These resources include:

• Bootstrap Providers
• Control Plane Providers
• Infrastructure Providers
• IPAM Providers

To get a sense of what's configurable, you can use kubectl explain. For example:

kubectl explain ipamprovider.spec.deployment.imagePullSecrets --api-version=operator.cluster.x-k8s.io/v1alpha2 --recursive
kubectl explain ipamprovider.spec.deployment.containers --api-version=operator.cluster.x-k8s.io/v1alpha2

These commands reveal the available configuration options, including imagePullSecrets and container image URLs. Armed with this knowledge, you can start customizing your provider deployments.

Implementing the Solution: Step-by-Step

To make these customizations easier, you can update your provider templates. Let’s walk through the specific changes for each provider type. We will cover kubeadm bootstrapprovider, kubeadm controlPlane provider, azure & nutanix infrastructure provider, cluster-api core provider, and in-cluster IPAM provider.

1. Kubeadm Bootstrap Provider

First up, the kubeadm bootstrap provider. Here's how you can modify the bootstrap.yaml and values to support custom images and imagePullSecrets:

• bootstrap.yaml:

  apiVersion: operator.cluster.x-k8s.io/v1alpha2
  kind: BootstrapProvider
  metadata:
    name: {{ $bootstrapName }}
    namespace: {{ $bootstrapNamespace }}
  spec:
  {{- if $bootstrap.deployment }}
    deployment: {{ toYaml $bootstrap.deployment | nindent 4 }}
  {{- end }}
  

• Values:

  bootstrap:
    kubeadm:
      deployment:
        imagePullSecrets:
        - name: <secret name>
        containers:
        - name: manager
          imageUrl: <private>/cluster-api/kubeadm-bootstrap-controller:v1.11.2
  

In this setup, we're adding a section to specify imagePullSecrets and a custom imageUrl for the manager container. This allows you to pull the kubeadm bootstrap controller image from your private registry. Remember to replace <secret name> and <private>/cluster-api/kubeadm-bootstrap-controller:v1.11.2 with your actual secret name and image URL.

2. Kubeadm Control Plane Provider

Next, let's tackle the kubeadm control plane provider. Similar to the bootstrap provider, you'll modify the bootstrap.yaml and values:

• bootstrap.yaml:

  apiVersion: operator.cluster.x-k8s.io/v1alpha2
  kind: ControlPlaneProvider
  metadata:
    name: {{ $controlPlaneName }}
    namespace: {{ $controlPlaneNamespace }}
  spec:
  {{- if $controlPlane.deployment }}
    deployment: {{ toYaml $controlPlane.deployment | nindent 4 }}
  {{- end }}
  

• Values:

  controlPlane:
    kubeadm:
      deployment:
        imagePullSecrets:
        - name: <secret name>
        containers:
        - name: manager
          imageUrl: <private>/cluster-api/kubeadm-control-plane-controller:v1.11.2
  

Again, we're injecting imagePullSecrets and a custom image URL. This ensures that the kubeadm control plane controller image is pulled from your private registry. It's all about consistency and control. Don't forget to update the placeholders with your specific values.

3. Azure & Nutanix Infrastructure Providers

Now, let's move on to infrastructure providers, specifically Azure and Nutanix. These providers often have additional deployments that need to be configured. Here’s how you can modify the infra.yaml and values:

• infra.yaml:

  apiVersion: operator.cluster.x-k8s.io/v1alpha2
  kind: InfrastructureProvider
  metadata:
    name: {{ $infrastructureName }}
    namespace: {{ $infrastructureNamespace }}
  spec:
  {{- if $infra.additionalDeployments }}
    additionalDeployments: {{ toYaml $infra.additionalDeployments | nindent 4 }}
  {{- end }}
  {{- if $infra.deployment }}
    deployment: {{ toYaml $infra.deployment | nindent 4 }}
  {{- end }}
  

• Values:

  infrastructure:
    azure:
      deployment:
        imagePullSecrets:
        - name: <secret name>
      containers:
      - name: manager
        imageUrl: <private>/cluster-api-azure/cluster-api-azure-controller:v1.21.1
      additionalDeployments:
        azureserviceoperator-controller-manager:
          deployment:
            imagePullSecrets:
            - name: <secret>
          containers:
          - imageUrl: <private>/k8s/azureserviceoperator:v2.11.0
            name: manager
    nutanix:
      deployment:
        imagePullSecrets:
        - name: <secret name>
      containers:
      - name: manager
        imageUrl: <private>/nutanix-cloud-native/cluster-api-provider-nutanix/controller:v1.7.2
  

Notice the additionalDeployments section. This is crucial for configuring deployments like the azureserviceoperator-controller-manager. By specifying imagePullSecrets and container image URLs for each deployment, you ensure that all images are pulled from your private registry. For Nutanix, the configuration is similar, focusing on the main deployment. Again, customize the placeholders with your actual values.

4. Cluster API Core Provider

The core provider is fundamental to Cluster API. Here’s how to configure it:

• core.yaml:

  apiVersion: operator.cluster.x-k8s.io/v1alpha2
  kind: CoreProvider
  metadata:
    name: {{ $coreName }}
    namespace: {{ $coreNamespace }}
  spec:
  {{- if $core.deployment }}
    deployment: {{ toYaml $core.deployment | nindent 4 }}
  {{- end }}
  

• Values:

  core:
    cluster-api:
      deployment:
        imagePullSecrets:
        - name: <secret>
      containers:
      - name: manager
        imageUrl: <private>/cluster-api/cluster-api-controller:v1.11.2
  

By modifying the core.yaml and providing the necessary values, you can ensure that the core Cluster API controller image is pulled from your private registry. Double-check your secret names and image URLs!

5. In-Cluster IPAM Provider

Last but not least, let's configure the in-cluster IPAM provider:

• ipam.yaml:

  apiVersion: operator.cluster.x-k8s.io/v1alpha2
  kind: IPAMProvider
  metadata:
    name: {{ $ipamName }}
    namespace: {{ $ipamNamespace }}
  spec:
  {{- if $ipam.deployment }}
    deployment: {{ toYaml $ipam.deployment | nindent 4 }}
  {{- end }}
  

• Values:

  ipam:
    in-cluster:
      deployment:
        imagePullSecrets:
        - name: <secret>
      containers:
      - name: manager
        imageUrl: <private>/capi-ipam-ic/cluster-api-ipam-in-cluster-controller:v1.0.3
  

With these changes, the IPAM controller image will also be pulled from your private registry. Consistency across all providers is key to a well-managed cluster.

Separating Config Secrets for Multiple Infrastructure Providers

Now, let's tackle another crucial aspect: managing configuration secrets when you have multiple infrastructure providers. Imagine you're using both Azure and Nutanix. The credentials for Azure have absolutely nothing to do with Nutanix, and vice versa. So, how do we keep things tidy and secure?

Why Separate Secrets?

Separating config secrets is a best practice for several reasons:

• Security: Limiting the scope of credentials reduces the potential impact of a breach. If one set of credentials is compromised, the damage is contained.
• Clarity: Separate secrets make it clear which credentials belong to which provider. This reduces confusion and the risk of misconfiguration.
• Maintainability: Managing separate secrets simplifies updates and rotations. You can update credentials for one provider without affecting others.

How to Implement Separate Secrets

The suggestion here is to update all provider templates to fetch additionalDeployments from specific provider values instead of a global $.Values.additionalDeployments. This means that the configuration for Azure deployments should be pulled from $.Values.infrastructure.azure.additionalDeployments, while Nutanix deployments should use $.Values.infrastructure.nutanix.additionalDeployments. This makes the configuration more modular and easier to manage.

It also makes sense to separate the configSecret itself. Instead of having a single secret that contains credentials for all providers, you should have separate secrets for each provider. This aligns with the principle of least privilege and enhances security.

Benefits of These Changes

Implementing these changes brings several benefits:

• Enhanced Security: By using private registries and separate secrets, you significantly improve the security posture of your cluster.
• Greater Control: You have more control over the images being deployed and the configurations being used.
• Improved Customization: You can tailor your deployments to your specific needs and requirements.
• Better Maintainability: Managing separate configurations simplifies updates and rotations.

Final Thoughts

So, there you have it! Managing imagePullSecrets, private registries, and separate configuration secrets in Cluster API is essential for production environments. By following these guidelines, you can ensure that your clusters are secure, well-managed, and tailored to your specific needs.

Remember, this is an ongoing discussion and a potential feature enhancement for Cluster API. If this sounds like something you'd like to see in the chart upstream, make your voice heard! Let's work together to make Cluster API even better.

If you found this helpful, give it a share and let's keep the conversation going! What are your thoughts on managing secrets and images in Cluster API? Let's chat in the comments!