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Embedded Cluster Config

This topic is a reference for the Replicated Embedded Cluster Config custom resource. For more information about Embedded Cluster, see Using Embedded Cluster.

note

Embedded Cluster is in beta. If you are instead looking for information about creating Kubernetes Installers with Replicated kURL, see the Replicated kURL section.

Overview​

To install your application with Embedded Cluster, an Embedded Cluster Config must be created in a release. Embedded Cluster installation artifacts are available only for releases that include an Embedded Cluster Config.

The Embedded Cluster Config lets you define several aspects of the Kubernetes cluster that will be created.

Limitations​

  • The Embedded Cluster Config does not support the use of Go template functions, including KOTS template functions.

For additional property-specific limitations, see the sections below.

Example​

apiVersion: embeddedcluster.replicated.com/v1beta1
kind: Config
spec:
  version: 1.19.0+k8s-1.30
  roles:
    controller:
      name: management
      labels:
        management: "true"
    custom:
    - name: app
      labels:
       app: "true"
  extensions:
    helm:
      repositories:
        - name: ingress-nginx
          url: https://kubernetes.github.io/ingress-nginx
      charts:
        - name: ingress-nginx
          chartname: ingress-nginx/ingress-nginx
          namespace: ingress-nginx
          version: "4.8.3"
          values: |
            controller:
              service:
                type: NodePort
                nodePorts:
                  http: "80"
                  https: "443"
              # Known issue: Only use image tags for multi-architecture images.
              # Set digest to empty string to ensure the air gap builder uses
              # single-architecture images.
              image:
                digest: ""
                digestChroot: ""
              admissionWebhooks:
                patch:
                  image:
                    digest: ""

version​

You must specify which version of Embedded Cluster to install. Each version of Embedded Cluster includes particular versions of components like KOTS (Admin Console) and OpenEBS.

For a full list of versions, see the Embedded Cluster releases page in GitHub. It's recommended to keep this version as up to date as possible because Embedded Cluster is changing rapidly.

roles​

You can optionally customize node roles in the Embedded Cluster Config using the roles key.

If the roles key is configured, users select one or more roles to assign to a node when it is joined to the cluster. A single node can be assigned:

  • The controller role, which designates nodes that run the Kubernetes control plane
  • One or more custom roles
  • Both the controller role and one or more custom roles

For more information about how to assign node roles in the Admin Console, see Managing Multi-Node Clusters with Embedded Cluster.

If the roles key is not configured, all nodes joined to the cluster are assigned the controller role. The controller role designates nodes that run the Kubernetes control plane. Controller nodes can also run other workloads, such as application or Replicated KOTS workloads.

For more information, see the sections below.

controller​

By default, all nodes joined to a cluster are assigned the controller role.

You can customize the controller role in the following ways:

  • Change the name that is assigned to controller nodes. By default, controller nodes are named “controller”. If you plan to create any custom roles, Replicated recommends that you change the default name for the controller role to a term that is easy to understand, such as "management". This is because, when you add custom roles, both the name of the controller role and the names of any custom roles are displayed to the user when they join a node.
  • Add one or more labels to be assigned to all controller nodes. See labels.

Example​

apiVersion: embeddedcluster.replicated.com/v1beta1
kind: Config
spec:
  roles:
    controller:
      name: management
      labels:
        management: "true" # Label applied to "management" nodes

custom​

You can add custom roles that users can assign to one or more nodes in the cluster. Each custom role that you add must have a name and can also have one or more labels. See labels.

Adding custom node roles is useful if you need to assign application workloads to specific nodes in multi-node clusters. For example, if your application has graphics processing unit (GPU) workloads, you could create a custom role that will add a gpu=true label to any node that is assigned the role. This allows you to then schedule GPU workloads on nodes labled gpu=true. Or, if your application includes any resource-intensive workloads (such as a database) that must be run on dedicated nodes, you could create a custom role that adds a db=true label to the node. This way, the database workload could be assigned to a certain node or nodes.

Example​

apiVersion: embeddedcluster.replicated.com/v1beta1
kind: Config
spec:
  roles:
    custom:
    - name: app
      labels:
        app: "true" # Label applied to "app" nodes

labels​

You can define Kubernetes labels for the default controller role and any custom roles that you add. When labels are defined, Embedded Cluster applies the label to any node in the cluster that is assigned the given role. Labels are useful for tasks like assigning workloads to nodes.

Example​

apiVersion: embeddedcluster.replicated.com/v1beta1
kind: Config
spec:
  roles:
    controller:
      name: management
      labels:
        management: "true" # Label applied to "management" nodes
    custom:
    - name: db
      labels:
        db: "true" # Label applied to "db" nodes
    - name: gpu
      labels:
        gpu: "true" # Label applied to "gpu" nodes

extensions​

If you need to install Helm charts before your application and as part of the Embedded Cluster itself, you can do this with Helm extensions. One situation where this is useful is if you want to ship an ingress controller, because Embedded Cluster does not yet include one.

Helm extensions are updated when new versions of your application are deployed from the Admin Console. So, for example, you can change the values for a Helm extension from one release to another, and those changes will be applied to the cluster when the new release is deployed.

The format for specifying Helm extensions uses the same k0s Helm extensions format from the k0s configuration. For more information about these fields, see the k0s documentation.

Limitation​

If a Helm extension is removed from the Embedded Cluster Config, the associated Helm chart is not removed from the cluster.

Requirements​

  • The version field is required. Failing to specify a chart version will cause problems for upgrades.

  • If you need to install multiple charts in a particular order, set the order field to a value greater than or equal to 10. Numbers below 10 are reserved for use by Embedded Cluster to deploy things like a storage provider and the Admin Console. If an order is not provided, Helm extensions are installed with order 10.

Example​

apiVersion: embeddedcluster.replicated.com/v1beta1
kind: Config
spec:
  extensions:
    helm:
      repositories:
        - name: ingress-nginx
          url: https://kubernetes.github.io/ingress-nginx
      charts:
        - name: ingress-nginx
          chartname: ingress-nginx/ingress-nginx
          namespace: ingress-nginx
          version: "4.8.3"
          values: |
            controller:
              service:
                type: NodePort
                nodePorts:
                  http: "80"
                  https: "443"
              # Known issue: Only use image tags for multi-architecture images.
              # Set digest to empty string to ensure the air gap builder uses
              # single-architecture images.
              image:
                digest: ""
                digestChroot: ""
              admissionWebhooks:
                patch:
                  image:
                    digest: ""

unsupportedOverrides​

important

This feature should be used with caution by advanced users who understand the risks and ramifications of changing the default configuration.

Unsupported overrides allow you to override Embedded Cluster's default configuration, including the k0s config and the Helm values for extensions like KOTS and OpenEBS. This should be used with caution because changes here are untested and can disrupt or break Embedded Clusters. Any issues that are caused by unsupported overrides are not supported.

While they should be used with caution, unsupported overrides are useful if you need to make changes that are not otherwise exposed by Embedded Cluster.

Override the k0s Config​

By default, Embedded Cluster uses a k0s config that is tested and known to work for Embedded Clusters. In some circumstances, you might want to change the k0s config.

For more information on the k0s config, see Configuration options in the k0s documentation.

For example, you can do the following to enable WireGuard-based encryption. Note that other configuration might be necessary. See spec.network.calico in the k0s documentation for more details.

apiVersion: embeddedcluster.replicated.com/v1beta1
kind: Config
spec:
  unsupportedOverrides:
    k0s: |
      config:
        spec:
          network:
            calico:
              wireguard: true

Limtiations​

  • The spec.api and spec.storage keys in the k0s config cannot be changed after installation. Whereas most keys in the k0s config apply to the whole cluster, these two keys are set for each node. Embedded Cluster cannot update these keys on each individual node during updates, so they cannot be changed after installation.

  • Overrides overwrite the corresponding fields in the k0s configuration. They are not merged into Embedded Cluster’s default configuration. When using overrides to override a list, for example, ensure that you include other elements in the list that Embedded Cluster includes by default.

Override the Helm Values for Built-In Extensions​

Embedded Cluster deploys built-in extensions like KOTS and OpenEBS to provide capabilities like storage and application management. These extensions are deployed with Helm, and the Helm values for each can be modified if necessary.

To modify these values, you can use the unsupportedOverrides.builtInExtensions key of the Embedded Cluster Config. Each chart you want to modify is an item in the array. The name key identifies the Helm chart that you want to modify, and the values key is a string where you specify your modified Helm values. Your modified values are merged into the values used by Embedded Cluster.

The following are the built-in extensions available for modification:

  • openebs
  • admin-console
  • velero
  • embedded-cluster-operator

Example​

apiVersion: embeddedcluster.replicated.com/v1beta1
kind: Config
spec:
  unsupportedOverrides:
    builtInExtensions:
    - name: openebs
      values: |
        key: value