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Embedded Cluster overview (Beta)

This topic provides an introduction to Replicated Embedded Cluster.

Overview​

Replicated Embedded Cluster allows you to distribute a Kubernetes cluster and your application together as a single appliance, making it easy for enterprise users to install, update, and manage the application and the cluster in tandem. Embedded Cluster is based on the open source Kubernetes distribution k0s. For more information, see the k0s documentation.

Software vendors can configure the Embedded Cluster Config manifest to define characteristics of the cluster and the installation. For example, you can add optional Helm extensions to deploy components in the cluster before Embedded Cluster installs your application.

For enterprise users, Embedded Cluster provides a built-in UI that guides users through installation and upgrades. Additionally, Embedded Cluster automatically updates the cluster infrastructure at the same time as application updates, allowing users to more easily keep the cluster up-to-date without needing to use kubectl.

Limitations​

  • Embedded Cluster v3 is Beta. The limitations and features are subject to change.

  • Embedded Cluster v3 (Beta) does not support disaster recovery.

  • Some Replicated template functions are not implemented in Embedded Cluster v3 (Beta). Contact Replicated if a missing template function blocks your release.

  • Embedded Cluster v3 (Beta) does not support custom node roles. You can assign nodes the controller or worker role.

Built-in extensions​

The built-in extensions installed by Embedded Cluster include:

  • OpenEBS: Embedded Cluster uses OpenEBS to provide local PersistentVolume (PV) storage. For more information, see the OpenEBS documentation.

  • Image registry: Embedded Cluster installs an image registry where it pushes the images required to install and run the application.

Embedded Cluster installs each built-in extension in its own namespace.

About installing with Embedded Cluster​

Embedded Cluster supports installations in online (internet-connected) environments and air gap environments with no outbound internet access.

To install, users first download and extract the Embedded Cluster installation assets. Then, users can choose to follow a guided installation with the UI or a headless install with the CLI.

During installation, Embedded Cluster automatically runs preflight checks to verify that the installation environment meets the requirements. Users then configure the application and can optionally add nodes to the cluster before deploying.

For more information about how to install with Embedded Cluster, see:

Embedded Cluster host preflight checks​

During installation, Embedded Cluster automatically runs a default set of host preflight checks. The default host preflight checks verify that the installation environment meets the requirements for Embedded Cluster, such as:

  • The system has sufficient disk space
  • The system has at least 2G of memory and 2 CPU cores
  • The system clock syncs

If any of the Embedded Cluster host preflight checks fail, Embedded Cluster blocks installation and displays a message describing the failure.

For the full default host preflight spec for Embedded Cluster, see preflight/embedded in the ec repository in GitHub.

Limitations​

Embedded Cluster host preflight checks have the following limitations:

  • Vendors cannot modify the default host preflight checks for Embedded Cluster or provide their own custom host preflight spec for Embedded Cluster.
  • Host preflight checks do not verify that the application meets any application-specific requirements. For more information about defining preflight checks for your application, see Define Preflight Checks.

Multi-node installations​

Embedded Cluster supports installations in mutli-node clusters. Your end customers can add nodes to a cluster during or after installation from the UI.

Embedded Cluster automatically enables high availability (HA) when at least three controller nodes are present in the cluster.

For more information, see Manage Multi-Node Clusters with Embedded Cluster.

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