Chapter 12. Setting the RHCOS version in a cluster

Procedure

1. Confirm that your cluster has the RHCOS 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.

2. Update the nodes by using one of the following procedures:

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

     1. Edit the OSImageStream custom resource by running the following command:

        $ oc edit osimagestream cluster

     2. 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.

     Important

     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

1. After the nodes have returned to the READY state, examine the /etc/redhat-release file to see the current RHCOS 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)