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Follow this guide to have an auto-deployed cluster via rke2/k3s and managed by Rancher with the only help of an Elemental Teal iso


What is Elemental Teal ?

Elemental Teal is the combination of "SLE Micro for Rancher" with the Rancher Elemental stack

SLE Micro for Rancher is a containerized and "stripped to the bones" operating system layer. It only requires grub2, dracut, a kernel, and systemd.

Its sole purpose is to run Kubernetes (k3s or RKE2), with everything controlled through Rancher Manager.

Elemental Teal is built in the openSUSE Build Service and available through the openSUSE Registry

What is the Rancher Elemental Stack ?

The Elemental Stack consists of some packages on top of SLE Micro for Rancher

  • elemental-toolkit - includes a set of OS utilities to enable OS management via containers. Includes dracut modules, bootloader configuration, cloud-init style configuration services, etc.
  • elemental-operator - this connects to Rancher Manager and handles machineRegistration and machineInventory CRDs
  • elemental-register - this registers machines via machineRegistrations and installs them via elemental-cli
  • elemental-cli - this installs any elemental-toolkit based derivative. Basically an installer based on our A/B install and upgrade system
  • rancher-system-agent - runs on the installed system and gets instructions ("Plans") from Rancher Manager what to install and run on the system


  • A Rancher server (2.6.9) configured (server-url set)
    • To configure the Rancher server-url please check the Rancher docs
  • A machine (bare metal or virtualized) with TPM 2.0
    • Hint 1: Libvirt allows setting virtual TPMs for virtual machines example here
    • Hint 2: You can enable TPM emulation on bare metal machines missing the TPM 2.0 module example here
  • Helm Package Manager (
  • Docker (for iso manipulation)

Preparing the cluster

elemental-operator is the management endpoint, running the management cluster and taking care of creating inventories, registrations for machines and much more.

We will use the Helm package manager to install the elemental-operator chart into our cluster

helm upgrade --create-namespace -n cattle-elemental-system --install elemental-operator oci://

There is a few options that can be set in the chart install but that is out of scope for this document. You can see all the values on the chart values.yaml

Now after a few seconds you should see the operator pod appear on the cattle-elemental-system namespace.

kubectl get pods -n cattle-elemental-systemNAME                                  READY   STATUS    RESTARTS   AGEelemental-operator-64f88fc695-b8qhn   1/1     Running   0          16s

Prepare your kubernetes resources

Node deployment starts with a MachineRegistration, identifying a set of machines sharing the same configuration (disk drives, network, etc.)

Then it continues with having a Cluster resource that uses a MachineInventorySelectorTemplate to know which machines are for that cluster.

This selector is a simple matcher based on labels set in the MachineInventory, so if your selector is matching the cluster-id key with a value myId and your MachineInventory has that same key with that value, it will match and be bootstrapped as part of the cluster.

You will need to create the following files.

apiVersion: MachineInventorySelectorTemplatemetadata:  name: my-machine-selector  namespace: fleet-defaultspec:  template:    spec:      selector:        matchExpressions:          - key: location            operator: In            values: [ 'europe' ]

As you can see this is a very simple selector that checks the key node-location for the value europe

kind: ClusterapiVersion:  name: my-cluster  namespace: fleet-defaultspec:  rkeConfig:    machinePools:      - controlPlaneRole: true        etcdRole: true        machineConfigRef:          apiVersion:          kind: MachineInventorySelectorTemplate          name: my-machine-selector        name: pool1        quantity: 1        unhealthyNodeTimeout: 0s        workerRole: true  kubernetesVersion: v1.23.7+k3s1

As you can see we are setting that our machineConfigRef is of Kind MachineInventorySelectorTemplate with the name my-machine-selector, which matches the selector we created.

apiVersion: MachineRegistrationmetadata:  name: my-nodes  namespace: fleet-defaultspec:  config:    cloud-config:      users:        - name: root          passwd: root    elemental:      install:        reboot: true        device: /dev/sda        debug: true  machineName: my-machine  machineInventoryLabels:    location: "europe"    manufacturer: "${System Information/Manufacturer}"    productName: "${System Information/Product Name}"    serialNumber: "${System Information/Serial Number}"    machineUUID: "${System Information/UUID}"

This creates a MachineRegistration which will provide a unique URL which we will use with elemental-register to register the node during installation, so the operator can create a MachineInventory which will be using to bootstrap the node. See that we set the label that match our selector here already, although it can always be added later to the MachineInventory.


Make sure to modify the registration.yaml above to set the proper install device to point to a valid device based on your node configuration(i.e. /dev/sda, /dev/vda, /dev/nvme0, etc...)

Now that we have all the configuration to create the proper resources in Kubernetes just apply them

kubectl apply -f selector.yaml kubectl apply -f cluster.yaml kubectl apply -f registration.yaml

Preparing the iso

Now this is the last step, we need to prepare an Elemental Teal iso that includes the initial registration config, so it can be auto registered, installed and fully deployed as part of our cluster. The contents of the file are nothing more than the registration url that the node needs to register and the proper server certificate, so it can connect securely. This iso then can be used to provision an infinite number of machines

Now, our MachineRegistration provides the needed config in its resource as part of its Status.RegistrationURL, so we can use that url to obtain the proper yaml needed for the iso.

wget --no-check-certificate `kubectl get machineregistration -n fleet-default my-nodes -o jsonpath="{.status.registrationURL}"` -O initial-registration.yaml

This will download the proper yaml from the registration URL and store it on the current directory under the initial-registration.yaml name.

Now we can proceed to create the ISO

We provide a ISO build script for ease of use that can get the final ISO and inject the initial-registration.yaml:

wget -q && chmod +x elemental-iso-add-registration

Now that we have the script we can proceed to download the ISO and inject our configuration injected:

./elemental-iso-add-registration initial-registration.yaml

This will generate an ISO on the current directory with the name elemental-teal-<ARCH>.iso


The script uses the iso for the arch based on the system is being run from. If you want to cross build for another system, you can set the ARCH environment variable to the desired target system (x86_64, aarch64) and the iso will be built for that architecture.

wget -q && chmod +x elemental-iso-build

Now that we have the script we can proceed to build the ISO with our configuration injected:

./elemental-iso-build initial-registration.yaml

This will generate an ISO on the current directory with the name elemental-<timestamp>.iso

You can now boot your nodes with this ISO, and they will:

  • Boot from the ISO
  • Register with the registrationURL given and create a per-machine MachineInventory
  • Install Elemental Teal to the given device
  • Restart
  • Auto-deploy the cluster via k3s

After a few minutes your new cluster will be fully provisioned!!

How can I choose the kubernetes version and deployer for the cluster?

In your cluster.yaml file there is a key in the Spec called kubernetesVersion. That sets the version and deployer that will be used for the cluster, for example for rke v1.23.6 while for rke2 would be v1.23.6+rke2r1 and for k3s v1.23.6+k3s1

To see all compatible versions check the Rancher Support Matrix PDF for rke/rke2/k3s versions and their components.

You can also check our Version doc to know how to obtain those versions.

Check our Cluster Spec page for more info about the Cluster resource.

How can I follow what is going on behind the scenes?

You should be able to follow along what the machine is doing via:

  • During ISO boot:
    • ssh into the machine (user/pass: root/ros):
      • running journalctl -f -t elemental will show you the output of the elemental-register and the elemental install
  • Once the system is installed:
    • On the Rancher UI -> Cluster Management you should see your new cluster and be able to see the Provisioning Log in the cluster details
    • ssh into the machine (user/pass: Whatever your configured on the registration.yaml under
      • running journalctl -f -u elemental-system-agent will show the output of the initial elemental config and install of rancher-system-agent
      • running journalctl -f -u rancher-system-agent will show the output of the boostrap of cluster components like k3s
      • running journalctl -f -u k3s will show the logs of the k3s deployment