Setting the RHCOS version in a cluster | Machine configuration

Updating the nodes in an existing cluster from FCOS 9 to FCOS 10
Additional resources

You can create an OKD cluster that uses Fedora CoreOS (FCOS) 10.x or update an existing cluster to FCOS 10.x, which is available as a Technology Preview feature in OKD 4.21.2 and greater. By running Fedora CoreOS (FCOS) 10.x as a Technology Preview feature, you can test how the operating system works with your cluster and your hardware, anticipate changes, and report bugs to Red Hat.

By default, FCOS 9.x is installed on OKD clusters starting with 4.13.

At any time, you can revert the cluster back to FCOS 9.x, if needed.

Using FCOS 10.x in an OKD cluster is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

For more information about the support scope of Red Hat Technology Preview features, see Technology Preview Features Support Scope.

FCOS is a purpose-designed operating system for use with containers that is deployed by default on all OKD nodes. Each version of FCOS is based on a specific version of Fedora. For OKD 4.13 and greater, the FCOS version is based on RHEL 9.x.

Running a cluster with FCOS 10.x is for testing purposes only on test clusters, and should not be used on production clusters. For example, by testing your cluster with FCOS 10.x, you can ensure that any existing hardware operates as expected with the new operating system.

You can use one of the following methods to run the nodes in a cluster on FCOS 10.x:

Upgrading an existing 4.21.2 or later cluster to FCOS 10.x. For more information, see "Updating the nodes in an existing cluster from FCOS 9 to FCOS 10".
Deploying FCOS 10.x on a new OKD cluster. For more information, see "Installation configuration parameters".

Updating the nodes in an existing cluster from FCOS 9 to FCOS 10

For an existing OKD 4.21.2 or later cluster, you can move the nodes in your machine config pool to Fedora CoreOS (FCOS) 10.x. By running Fedora CoreOS (FCOS) 10.x as a Technology Preview feature, you can test how the operating system works with your cluster and your hardware, anticipate changes, and report bugs to Red Hat.

Use the following procedure for an OKD 4.22.x cluster. For an OKD 4.21.x cluster that is 4.21.2 or later, see the How to deploy a RHCOS 10 OKD cluster knowledgebase article.

Running a cluster with a mixture of RHCOS 9.x and 10.x nodes is not supported. You must move all of your nodes to RHCOS 10.x.

Prerequisites

You have updated the boot image in your cluster to at least FCOS 9.x. Note that the boot image on each node remains at FCOS 9.x after installing or upgrading to FCOS 10.x. After you configure FCOS 10.x in your cluster, new nodes boot using FCOS 9.x initially and automatically upgrade to FCOS 10.x. For more information, see "Manually updating the boot image".
You have enabled the TechPreviewNoUpgrade feature set in your cluster’s FeatureGate custom resource (CR). For more information, see "Enabling features using feature gates".

Procedure

Confirm that your cluster has the FCOS 10.x stream available by running the following command:
```
$ oc get osImageStreams/cluster -o yaml | grep rhel-10
```
Example output
```
  - name: rhel-10
```
It can take several minutes for the osImageStream object to become available after you enable the TechPreviewNoUpgrade feature set.

Update the nodes by using one of the following procedures:

Update all of the nodes in your cluster to RHCOS 10:

Edit the OSImageStream custom resource by running the following command:
```
$ oc edit osimagestream cluster
```

Add or edit the defaultStream parameter to specify rhel-10:

apiVersion: machineconfiguration.openshift.io/v1alpha1
kind: OSImageStream
metadata:
  annotations:
    machineconfiguration.openshift.io/release-image-version: c4a08067821f304642e731fdcca0c8c6a6b19484
  creationTimestamp: "2026-04-13T17:27:41Z"
  generation: 1
  name: cluster
  resourceVersion: "36503"
  uid: f2ef4c15-4c1b-4117-850e-ae6adf408c4f
spec:
  defaultStream: rhel-10
status:
  availableStreams:
  - name: rhel-10
    osExtensionsImage: quay.io/openshift-release-dev/ocp-v4.0-art-dev@sha256:34baf90f333d89690a2f99b3ab746f8a43fee99b1218a8a058f75231f7c7ab53
    osImage: quay.io/openshift-release-dev/ocp-v4.0-art-dev@sha256:b208f0f861d009008b43a103e64d087f6da59e480bb0292d401895e041095da7
  - name: rhel-9
    osExtensionsImage: quay.io/openshift-release-dev/ocp-v4.0-art-dev@sha256:4aa864da633b1ce0a3612992a75849ff2b7d289699fa9b9b400522371a77d3ea
    osImage: quay.io/openshift-release-dev/ocp-v4.0-art-dev@sha256:cb34964bd5d957a1226e9fb082a591b650eca339ebd4aad15343d02fc21130dd
  defaultStream: rhel-9

The spec.defaultStream: rhel-10 parameter directs the Machine Config Operator (MCO) to update the nodes to the image referenced in status.availableStreams.osImage value under name: rhel-10.

Update all machine config pools to RHCOS 10:
1. Update the worker machine config pool to RHCOS 10 by using the following command:
  
  $ oc patch mcp worker --type merge -p '{"spec":{"osImageStream":{"name":"rhel-10"}}}'
2. Update the control plane machine config pool to RHCOS 10 by using the following command:
  
  $ oc patch mcp master --type merge -p '{"spec":{"osImageStream":{"name":"rhel-10"}}}'
3. Update all custom machine config pools to RHCOS 10 by using the following command with the name of the machine config pool to update:
  
  $ oc patch mcp <mcp_name> --type merge -p '{"spec":{"osImageStream":{"name":"rhel-10"}}}'
  
  Replace <mcp_name> with the names of the custom machine config pools to update.
Running a cluster with a mixture of RHCOS 9.x and 10.x nodes is not supported. You must move all of your nodes to RHCOS 10.x.

Wait for the pools to finish rolling out the update.

Verification

After the nodes have returned to the READY state, examine the /etc/redhat-release file to see the current FCOS version on the nodes:
1. Log in to a node by using the following command:
  $ oc debug node/<node_name>
  Replace <node_name> with the name of the node.
2. Set /host as the root directory within the debug shell by using the following command:
  $ chroot /host
3. Look at the contents of the /etc/redhat-release file by using the following command:
  $ cat /etc/redhat-release
  The output should appear similar to the following example:
  Example output
  Red Hat Enterprise Linux release 10.2 (Coughlan)

Setting the FCOS version in a cluster

Updating the nodes in an existing cluster from FCOS 9 to FCOS 10

Additional resources