Questo contenuto non è disponibile nella lingua selezionata.

Chapter 8. Image mode for OpenShift

You can extend the functionality of your base RHCOS image by layering additional images onto the base image. This layering does not modify the base RHCOS image. Instead, it creates a custom layered image that includes all RHCOS functionality and adds additional functionality to specific nodes in the cluster.

Image mode is a cloud-native approach to operating system management that treats your OS like a container image. You define your operating system configuration as code, build it as a unified image, and deploy it consistently across your entire fleet.

8.1. About image mode for OpenShift
Copia collegamento

Image mode for OpenShift allows you to customize the underlying node operating system on any of your cluster nodes. This helps keep everything up-to-date, including the node operating system and any added customizations such as specialized software.

You create a custom layered image by using a Containerfile and applying it to nodes by using a custom object. At any time, you can remove the custom layered image by deleting that custom object.

With image mode for OpenShift, you can install RPMs into your base image, and your custom content will be booted alongside RHCOS. The Machine Config Operator (MCO) can roll out these custom layered images and monitor these custom containers in the same way it does for the default RHCOS image. Image mode for OpenShift gives you greater flexibility in how you manage your RHCOS nodes.

Important

Installing realtime kernel and extensions RPMs as custom layered content is not recommended. This is because these RPMs can conflict with RPMs installed by using a machine config. If there is a conflict, the MCO enters a degraded state when it tries to install the machine config RPM. You need to remove the conflicting extension from your machine config before proceeding.

When you apply the custom layered image to your cluster, you assume the responsibility for the package you applied with the custom layered image and any issues that might arise with the package.

There are three methods for deploying a custom layered image onto your nodes:

On-cluster image mode: With on-cluster image mode, you create a MachineOSConfig object where you include the Containerfile and other parameters. The build is performed on your cluster and the resulting custom layered image is automatically pushed to your repository and applied to the machine config pool that you specified in the MachineOSConfig object. The entire process is performed completely within your cluster.
Out-of-cluster image mode: With out-of-cluster image mode, you create a Containerfile that references an OpenShift Container Platform image and the RPM that you want to apply, build the layered image in your own environment, and push the image to your repository. Then, in your cluster, create a MachineConfig object for the targeted node pool that points to the new image. The Machine Config Operator overrides the base RHCOS image, as specified by the osImageURL value in the associated machine config, and boots the new image.
During OpenShift Container Platform installation: You can apply a pre-built custom layered image to specific nodes during OpenShift Container Platform installation.

Important

For these methods, use the same base RHCOS image installed on the rest of your cluster. Use the oc adm release info --image-for rhel-coreos command to obtain the base image used in your cluster.

8.2. Example Containerfiles
Copia collegamento

Image mode for OpenShift allows you to use the following types of images to create custom layered images:

OpenShift Container Platform Hotfixes. You can work with Customer Experience and Engagement (CEE) to obtain and apply Hotfix packages on top of your RHCOS image. In some instances, you might want a bug fix or enhancement before it is included in an official OpenShift Container Platform release. Image mode for OpenShift allows you to easily add the Hotfix before it is officially released and remove the Hotfix when the underlying RHCOS image incorporates the fix.

Important

Some Hotfixes require a Red Hat Support Exception and are outside of the normal scope of OpenShift Container Platform support coverage or life cycle policies.

Hotfixes are provided to you based on Red Hat Hotfix policy. Apply it on top of the base image and test that new custom layered image in a non-production environment. When you are satisfied that the custom layered image is safe to use in production, you can roll it out on your own schedule to specific node pools. For any reason, you can easily roll back the custom layered image and return to using the default RHCOS.

Example on-cluster Containerfile to apply a Hotfix

containerfileArch: noarch
content: |-
  FROM configs AS final
  #Install hotfix package
  RUN dnf update -y https://example.com/files/systemd-252-46.el9_4.x86_64.rpm \
                    https://example.com/files/systemd-journal-remote-252-46.el9_4.x86_64.rpm \
                    https://example.com/files/systemd-libs-252-46.el9_4.x86_64.rpm  \
                    https://example.com/files/systemd-pam-252-46.el9_4.x86_64.rpm \
                    https://example.com/files/systemd-udev-252-46.el9_4.x86_64.rpm \
                    https://example.com/files/systemd-rpm-macros-252-46.el9_4.noarch.rpm && \
      dnf clean all && \
      bootc container lint

Example out-of-cluster Containerfile to apply a Hotfix

FROM quay.io/openshift-release-dev/ocp-v4.0-art-dev@sha256...
#Install hotfix package
RUN dnf update -y https://example.com/files/systemd-252-46.el9_4.x86_64.rpm \
                  https://example.com/files/systemd-journal-remote-252-46.el9_4.x86_64.rpm \
                  https://example.com/files/systemd-libs-252-46.el9_4.x86_64.rpm  \
                  https://example.com/files/systemd-pam-252-46.el9_4.x86_64.rpm \
                  https://example.com/files/systemd-udev-252-46.el9_4.x86_64.rpm \
                  https://example.com/files/systemd-rpm-macros-252-46.el9_4.noarch.rpm && \
    dnf clean all && \
    bootc container lint

RHEL packages. You can download Red Hat Enterprise Linux (RHEL) packages from the Red Hat Customer Portal, such as chrony, firewalld, and iputils.

Example out-of-cluster Containerfile to apply the rsyslog utility

# Using a 4.18.0 image
FROM quay.io/openshift-release-dev/ocp-v4.0-art-dev@sha256...
# Install rsyslog package
RUN dnf install -y rsyslog && \
    bootc container lint
# Copy your custom configuration in
ADD remote.conf /etc/rsyslog.d/remote.conf

Third-party packages. You can download and install RPMs from third-party organizations, such as the following types of packages:

Bleeding edge drivers and kernel enhancements to improve performance or add capabilities.
Forensic client tools to investigate possible and actual break-ins.
Security agents.
Inventory agents that provide a coherent view of the entire cluster.
SSH Key management packages.

Example on-cluster Containerfile to apply a third-party package from EPEL

FROM configs AS final

#Enable EPEL (more info at https://docs.fedoraproject.org/en-US/epel/ ) and install htop
RUN dnf install -y https://dl.fedoraproject.org/pub/epel/epel-release-latest-9.noarch.rpm && \
    dnf install -y htop && \
    dnf clean all && \
    bootc container lint

Example out-of-cluster Containerfile to apply a third-party package from EPEL

# Get RHCOS base image of target cluster `oc adm release info --image-for rhel-coreos`
FROM quay.io/openshift-release-dev/ocp-v4.0-art-dev@sha256...

#Enable EPEL (more info at https://docs.fedoraproject.org/en-US/epel/ ) and install htop
RUN dnf install -y https://dl.fedoraproject.org/pub/epel/epel-release-latest-9.noarch.rpm && \
    dnf install -y htop && \
    dnf clean all && \
    bootc container lint

This Containerfile installs the RHEL fish program. Because fish requires additional RHEL packages, the image must be built on an entitled RHEL host. For RHEL entitlements to work, you must copy the etc-pki-entitlement secret into the openshift-machine-config-operator namespace.

Example on-cluster Containerfile to apply a third-party package that has RHEL dependencies

FROM configs AS final

# RHEL entitled host is needed here to access RHEL packages
# Install fish as third party package from EPEL
RUN dnf install -y https://dl.fedoraproject.org/pub/epel/9/Everything/x86_64/Packages/f/fish-3.3.1-3.el9.x86_64.rpm && \
    dnf clean all && \
    bootc container lint

Example out-of-cluster Containerfile to apply a third-party package that has RHEL dependencies

# Get RHCOS base image of target cluster `oc adm release info --image-for rhel-coreos`
FROM quay.io/openshift-release-dev/ocp-v4.0-art-dev@sha256...

# RHEL entitled host is needed here to access RHEL packages
# Install fish as third party package from EPEL
RUN dnf install -y https://dl.fedoraproject.org/pub/epel/9/Everything/x86_64/Packages/f/fish-3.3.1-3.el9.x86_64.rpm && \
    dnf clean all && \
    bootc container lint

After you create the machine config, the Machine Config Operator (MCO) performs the following steps:

Renders a new machine config for the specified pool or pools.
Performs cordon and drain operations on the nodes in the pool or pools.
Writes the rest of the machine config parameters onto the nodes.
Applies the custom layered image to the node.
Reboots the node using the new image.

Important

It is strongly recommended that you test your images outside of your production environment before rolling out to your cluster.

8.3. About on-cluster image mode
Copia collegamento

You can use the image mode for OpenShift on-cluster build process to apply a custom layered image to your nodes by creating a MachineOSConfig custom resource (CR), as described in "Using On-cluster image mode to apply a custom layered image".

When you create the object, the Machine Config Operator (MCO) creates a MachineOSBuild object and a builder pod. The process also creates transient objects, such as config maps, which are cleaned up after the build is complete. The MachineOSBuild object and the associated builder-* pod use the same naming scheme, <MachineOSConfig_CR_name>-<hash>, for example:

Example MachineOSBuild object

NAME                                             PREPARED   BUILDING   SUCCEEDED   INTERRUPTED   FAILED
layered-image-c8765e26ebc87e1e17a7d6e0a78e8bae   False      False      True        False         False

Example builder pod

NAME                                                      READY   STATUS      RESTARTS        AGE
build-layered-image-c8765e26ebc87e1e17a7d6e0a78e8bae      2/2     Running     0               11m

You should not need to interact with these new objects or the machine-os-builder pod. However, you can use all of these resources for troubleshooting, if necessary.

When the build is complete, the MCO pushes the new custom layered image to your repository and rolls the image out to the nodes in the associated machine config pool. You can see the digested image pull spec for the new custom layered image in the MachineOSConfig object. This is now the active image pull spec for this MachineOSConfig.

Example digested image pull spec

apiVersion: machineconfiguration.openshift.io/v1
kind: MachineOSConfig
metadata:
  annotations:
    machineconfiguration.openshift.io/current-machine-os-build: layered-9a8f89455246fa0c42ecee6ff1fa1a45
  labels:
    machineconfiguration.openshift.io/createdByOnClusterBuildsHelper: ""
  name: layered-image
# ...
status:
  currentImagePullSpec: image-registry.openshift-image-registry.svc:5000/openshift-machine-config-operator/os-image@sha256:3c8fc667adcb432ce0c83581f16086afec08a961dd28fed69bb6bad6db0a0754

Tip

You can test a MachineOSBuild object to make sure it builds correctly without rolling out the custom layered image to active nodes by using a custom machine config pool that contains non-production nodes. Alternatively, you can use a custom machine config pool that has no nodes. The MachineOSBuild object builds even if there are no nodes for the MCO to deploy the custom layered image onto.

You can apply a custom layered image to any machine config pool in your cluster, including the control plane, worker, or custom pools.

Note

For single-node OpenShift clusters, you can apply a custom layered image to the control plane node only.

Making certain changes to a MachineOSConfig object triggers an automatic rebuild of the associated custom layered image. You can mitigate the effects of the rebuild by pausing the machine config pool where the custom layered image is applied as described in "Pausing the machine config pools". While the pools are paused, the MCO does not roll out the newly built image to the nodes after the build is complete. However, the build runs regardless of whether the pool is paused or not. For example, if you want to remove and replace a MachineOSCOnfig object, pausing the machine config pools before making the change prevents the MCO from reverting the associated nodes to the base image, reducing the number of reboots needed.

When a machine config pool is paused, the oc get machineconfigpools reports the following status:

Example output

NAME      CONFIG                                              UPDATED   UPDATING   DEGRADED   MACHINECOUNT   READYMACHINECOUNT   UPDATEDMACHINECOUNT   DEGRADEDMACHINECOUNT   AGE
master    rendered-master-a0b404d061a6183cc36d302363422aba    True      False      False      3              3                   3                     0                      4h14m
worker    rendered-worker-221507009cbcdec0eec8ab3ccd789d18    False     False      False      2              2                   2                     0                      4h14m

1: The worker machine config pool is paused, as indicated by the three False statuses and the READYMACHINECOUNT at 0.

After the changes have been rolled out, you can unpause the machine config pool.

In the case of a build failure, for example due to network issues or an invalid secret, the MCO retries the build three additional times before the job fails. The MCO creates a different build pod for each build attempt. Note that the MCO automatically removes these build pods after a short period of time. Also, the affected machine config pool reports a build failure through the ImageBuildDegraded status condition. You can use the build pod logs to troubleshoot any build failures.

Example failed MachineOSBuild object

NAME                                             PREPARED   BUILDING   SUCCEEDED   INTERRUPTED   FAILED   AGE
layered-image-c8765e26ebc87e1e17a7d6e0a78e8bae   False      False      False        False        True     12m

You can manually rebuild your custom layered image by either modifying your MachineOSConfig object or applying an annotation to the MachineOSConfig object. For more information, see "Rebuilding an on-cluster custom layered image".

If you used a custom machine config pool to apply an on-cluster layered image to a node, you can remove the custom layered image from the node and revert to the base image. For more information, see "Reverting an on-cluster layered node".

You can modify an on-custom layered image as needed, to install additional packages, remove existing packages, change repositories, update secrets, or other similar changes, by editing the MachineOSConfig object. For more information, see "Modifying a custom layered image".

8.3.1. On-cluster image mode known limitations
Copia collegamento

Note the following limitations when working with the on-cluster layering feature:

On-cluster image mode is not supported on multi-architecture compute machines.
Using multiple MachineOSConfig objects on the same machine config pool is not supported. You need a separate MachineOSConfig CR for each machine config pool where you want to use a distinct custom layered image.
If you scale up a machine set that uses a custom layered image, the nodes reboot two times. The first, when the node is initially created with the base image and a second time when the custom layered image is applied.
Node disruption policies are not supported on nodes with a custom layered image. However, the following machine configuration changes do not cause a new image build or the reboot of a node with an on-cluster custom layered image:
- Modifying the configuration files in the /var or /etc directory
- Adding or modifying a systemd service
- Changing SSH keys
- Removing mirroring rules from ICSP, ITMS, and IDMS objects
- Changing the trusted CA, by updating the user-ca-bundle configmap in the openshift-config namespace
The following machine configuration changes do cause a new image build and a node reboot:
- Changing the kernel arguments
- Changing the OSImageURL parameter
- Adding or removing extensions
The images used in creating custom layered images take up space in your push registry. Always be aware of the free space in your registry and prune the images as needed. You can automatically remove an on-cluster custom layered image from the repository by deleting the MachineOSBuild object that created the image. Note that the credentials provided by the registry push secret must also grant permission to delete an image from the registry. For more information, see "Removing an on-cluster custom layered image".

Additional resources

8.3.2. Using the on-cluster image mode to apply a custom layered image
Copia collegamento

To apply a custom layered image to your cluster by using the on-cluster build process, create a MachineOSConfig custom resource (CR) that specifies the following parameters:

the Containerfile to build
the machine config pool to associate the build
where the final image should be pushed and pulled from
the push and pull secrets to use

You can create only one MachineOSConfig CR for each machine config pool.

Prerequisites

You have the pull secret in the openshift-machine-config-operator namespace that the Machine Config Operator (MCO) needs in order to pull the base operating system image from your repository. By default, the MCO uses the cluster global pull secret, which it synchronizes into the openshift-machine-config-operator namespace. You can add your pull secret to the OpenShift Container Platform global pull secret or you can use a different pull secret. For information on modifying the global pull secret, see "Updating the global cluster pull secret".
You have the push secret of the registry that the MCO needs to push the new custom layered image to. The credentials provided by the secret must also grant permission to delete an image from the registry.
Note
In a disconnected environment, ensure that the disconnected cluster can access the registry where you want to push the image. Image mirroring applies only to pulling images.
You have the pull secret that your nodes need to pull the new custom layered image from your registry. This should be a different secret than the one used to push the image to the repository.
You are familiar with how to configure a Containerfile. Instructions on how to create a Containerfile are beyond the scope of this documentation.
Optional: You have a separate machine config pool for the nodes where you want to apply the custom layered image. One benefit to having a custom machine config pool for the nodes it that you can easily revert to the base image, if needed. For more information, see "Reverting an on-cluster layered node".

Procedure

Create a MachineOSconfig object:
1. Create a YAML file similar to the following:
  apiVersion: machineconfiguration.openshift.io/v1
  1
  kind: MachineOSConfig metadata: name: layered-image
  2
  spec: machineConfigPool: name: layered-image
  3
  containerFile:
  4
  - containerfileArch: NoArch
  5
  content: |- FROM configs AS final RUN dnf install -y cowsay && \ dnf clean all && \ bootc container lint imageBuilder:
  6
  imageBuilderType: Job baseImagePullSecret:
  7
  name: global-pull-secret-copy renderedImagePushSpec: image-registry.openshift-image-registry.svc:5000/openshift/os-image:latest
  8
  renderedImagePushSecret:
  9
  name: builder-dockercfg-mtcl23
  1
  Specifies the machineconfiguration.openshift.io/v1 API that is required for MachineConfig CRs.
  2
  Specifies a name for the MachineOSConfig object. The name must match the name of the associated machine config pool. This name is used with other on-cluster image mode resources. The examples in this documentation use the name layered-image.
  3
  Specifies the name of the machine config pool associated with the nodes where you want to deploy the custom layered image. The examples in this documentation use the layered-image machine config pool.
  4
  Specifies the Containerfile to configure the custom layered image.
  5
  Specifies the architecture this containerfile is to be built for: ARM64, AMD64, PPC64LE, S390X, or NoArch. The default is NoArch, which defines a Containerfile that can be applied to any architecture.
  6
  Specifies the name of the image builder to use. This must be Job, which is a reference to the job object that is managing the image build.
  7
  Optional: Specifies the name of the pull secret that the MCO needs to pull the base operating system image from the registry. By default, the global pull secret is used.
  8
  Specifies the image registry to push the newly-built custom layered image to. This can be any registry that your cluster has access to in the host[:port][/namespace]/name or svc_name.namespace.svc[:port]/repository/name:<tag> format. This example uses the internal OpenShift Container Platform registry. You can specify a mirror registry if you cluster is properly configured to use a mirror registry.
  9
  Specifies the name of the push secret that the MCO needs to push the newly-built custom layered image to that registry.
2. Create the MachineOSConfig object:
  $ oc create -f <filename>.yaml
If necessary, when the MachineOSBuild object has been created and is in the READY state, modify the node spec for the nodes where you want to use the new custom layered image:
1. Check that the MachineOSBuild object is ready, by running the following command:
  $ oc get machineosbuild
  When the SUCCEEDED value is True, the build is complete:
  Example output showing that the MachineOSBuild object is ready
  NAME PREPARED BUILDING SUCCEEDED INTERRUPTED FAILED AGE layered-image-ad5a3cad36303c363cf458ab0524e7c0-builder False False True False False 43s
2. Edit the nodes where you want to deploy the custom layered image by adding a label for the machine config pool you specified in the MachineOSConfig object:
  $ oc label node <node_name> 'node-role.kubernetes.io/<mcp_name>='
  where:
  node-role.kubernetes.io/<mcp_name>=
  Specifies a node selector that identifies the nodes to deploy the custom layered image.
  When you save the changes, the MCO drains, cordons, and reboots the nodes. After the reboot, the node uses the new custom layered image.

Verification

Verify that the new pods are ready by running the following command:

$ oc get pods -n openshift-machine-config-operator

Example output

NAME                                                                    READY   STATUS    RESTARTS   AGE
build-layered-image-ad5a3cad36303c363cf458ab0524e7c0-hxrws              2/2     Running   0          2m40s


# ...
machine-os-builder-6fb66cfb99-zcpvq                                     1/1     Running   0          2m42s

1: This is the build pod where the custom layered image is building, named in the build-<MachineOSConfig_CR_name>-<hash> format.
2: This pod can be used for troubleshooting.

Verify the custom layered image build by running a command similar to the following:

$ oc get machineconfigpool <mcp_name> -o yaml

Example output

apiVersion: machineconfiguration.openshift.io/v1
kind: MachineConfigPool
metadata:
  labels:
    machineconfiguration.openshift.io/mco-built-in: ""
    pools.operator.machineconfiguration.openshift.io/layered: ""
  name: layered
# ...
status:
# ...
  conditions
# ...
  - lastTransitionTime: "2025-09-09T13:43:35Z"
    message: 'Failed to build OS image for pool worker (MachineOSBuild: worker-2d03dc921ff0c242c5892a3ef1ed1608):
      Failed: Build Failed'
    reason: BuildFailed
    status: "True"


    type: ImageBuildDegraded

1: Indicates whether the custom layered image build failed. If False, the build succeeded. If True, the build failed. You can use the build pod logs to troubleshoot any build failures.

Verify the current stage of your layered build by running the following command:

$ oc get machineosbuilds

Example output

NAME                                             PREPARED   BUILDING   SUCCEEDED   INTERRUPTED   FAILED   AGE
layered-image-ad5a3cad36303c363cf458ab0524e7c0   False      True       False       False         False    12m

1: The MachineOSBuild is named in the <MachineOSConfig_CR_name>-<hash> format.

The build is complete when BUILDING is False and SUCCEEDED is True.

When the build is complete, verify that the image has been applied to the nodes in the affected pool by running a command similar to the following:

$ oc describe machineconfignode/<machine_config_node_name>

Example machine config node output

Name:         ip-10-0-14-86.us-west-1.compute.internal
API Version:  machineconfiguration.openshift.io/v1
Kind:         MachineConfigNode
# ...
Spec:
  Config Image:
    Desired Image:  image-registry.openshift-image-registry.svc:5000/openshift-machine-config-operator/ocb-image@sha256:b485378fd8f7963ed74f14ce64f4f1e511e1601d49302b3046b1b78a83f539e3


  Config Version:
    Desired:  rendered-worker-d63c7736923b60b8b82492ae9a1eef40
  Node:
    Name:  ip-10-0-14-86.us-west-1.compute.internal
  Pool:
    Name:  worker
# ...
Status:
  Conditions:
# ...
    Message:               Action during update to image-registry.openshift-image-registry.svc:5000/openshift-machine-config-operator/ocb-image@sha256:b485378fd8f7963ed74f14ce64f4f1e511e1601d49302b3046b1b78a83f539e3: Successfully pulled OS image image-registry.openshift-image-registry.svc:5000/openshift-machine-config-operator/ocb-image@sha256:b485378fd8f7963ed74f14ce64f4f1e511e1601d49302b3046b1b78a83f539e3 from registry
    Reason:                ImagePulledFromRegistry
    Status:                False
    Type:                  ImagePulledFromRegistry
# ...
  Config Image:
    Current Image:  image-registry.openshift-image-registry.svc:5000/openshift-machine-config-operator/ocb-image@sha256:b485378fd8f7963ed74f14ce64f4f1e511e1601d49302b3046b1b78a83f539e3
    Desired Image:  image-registry.openshift-image-registry.svc:5000/openshift-machine-config-operator/ocb-image@sha256:b485378fd8f7963ed74f14ce64f4f1e511e1601d49302b3046b1b78a83f539e3
# ...

1: Digested image pull spec for the new custom layered image.

Important

The ImagePulledFromRegistry condition 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.

Verify that the MachineOSConfig object contains a reference to the new custom layered image by running the following command:

$ oc describe machineosconfig <object_name>

Example digested image pull spec

apiVersion: machineconfiguration.openshift.io/v1
kind: MachineOSConfig
metadata:
  annotations:
    machineconfiguration.openshift.io/current-machine-os-build: layered-9a8f89455246fa0c42ecee6ff1fa1a45
  labels:
    machineconfiguration.openshift.io/createdByOnClusterBuildsHelper: ""
  name: layered-image
# ...
status:
  currentImagePullSpec: image-registry.openshift-image-registry.svc:5000/openshift-machine-config-operator/os-image@sha256:3c8fc667adcb432ce0c83581f16086afec08a961dd28fed69bb6bad6db0a0754

1: Digested image pull spec for the new custom layered image.

Verify that the appropriate nodes are using the new custom layered image:

Start a debug session as root for a control plane node by running the following command:
```
$ oc debug node/<node_name>
```
Set /host as the root directory within the debug shell:
```
sh-4.4# chroot /host
```

Run the rpm-ostree status command to view that the custom layered image is in use:

sh-5.1# rpm-ostree status

Example output

# ...
Deployments:
* ostree-unverified-registry:image-registry.openshift-image-registry.svc:5000/openshift-machine-config-operator/os-images@sha256:3c8fc667adcb432ce0c83581f16086afec08a961dd28fed69bb6bad6db0a0754
                   Digest: sha256:3c8fc667adcb432ce0c83581f16086afec08a961dd28fed69bb6bad6db0a0754


                  Version: 419.94.202502100215-0 (2025-02-12T19:20:44Z)

1: Digested image pull spec for the new custom layered image.

Additional resources

8.3.3. Modifying an on-cluster custom layered image
Copia collegamento

You can modify an on-cluster custom layered image, as needed. This allows you to install additional packages, remove existing packages, change the pull or push repositories, update secrets, or other similar changes. You can edit the MachineOSConfig object, apply changes to the YAML file that created the MachineOSConfig object, or create a new YAML file for that purpose.

If you modify and apply the MachineOSConfig object YAML or create a new YAML file, the YAML overwrites any changes you made directly to the MachineOSConfig object itself.

When a machine config pool is paused, the oc get machineconfigpools reports the following status:

Example output

NAME      CONFIG                                              UPDATED   UPDATING   DEGRADED   MACHINECOUNT   READYMACHINECOUNT   UPDATEDMACHINECOUNT   DEGRADEDMACHINECOUNT   AGE
master    rendered-master-a0b404d061a6183cc36d302363422aba    True      False      False      3              3                   3                     0                      4h14m
worker    rendered-worker-221507009cbcdec0eec8ab3ccd789d18    False     False      False      2              2                   2                     0                      4h14m

1: The worker machine config pool is paused, as indicated by the three False statuses and the READYMACHINECOUNT at 0.

After the changes have been rolled out, you can unpause the machine config pool.

Prerequisites

You have opted in to on-cluster image mode by creating a MachineOSConfig object.

Procedure

Modify an object to update the associated custom layered image:
1. Edit the MachineOSConfig object to modify the custom layered image. The following example adds the rngd daemon to nodes that already have the tree package that was installed using a custom layered image.
  apiVersion: machineconfiguration.openshift.io/v1 kind: MachineOSConfig metadata: name: layered-image spec: machineConfigPool: name: layered-image containerFile: - containerfileArch: noarch content: |-
  1
  FROM configs AS final RUN rpm-ostree install rng-tools && \ systemctl enable rngd && \ rpm-ostree cleanup -m && \ bootc container lint RUN rpm-ostree install tree && \ bootc container lint imageBuilder: imageBuilderType: PodImageBuilder baseImagePullSecret: name: global-pull-secret-copy
  2
  renderedImagePushspec: image-registry.openshift-image-registry.svc:5000/openshift-machine-config-operator/os-images:latest
  3
  renderedImagePushSecret:
  4
  name: new-secret-name
  1
  Optional: Modify the Containerfile, for example to add or remove packages.
  2
  Optional: Update the secret needed to pull the base operating system image from the registry.
  3
  Optional: Modify the image registry to push the newly built custom layered image to.
  4
  Optional: Update the secret needed to push the newly built custom layered image to the registry.
  When you save the changes, the MCO drains, cordons, and reboots the nodes. After the reboot, the node uses the cluster base Red Hat Enterprise Linux CoreOS (RHCOS) image. If your changes modify a secret only, no new build is triggered and no reboot is performed.

Verification

Verify that the new MachineOSBuild object was created by using the following command:

$ oc get machineosbuild

Example output

NAME                                             PREPARED   BUILDING   SUCCEEDED   INTERRUPTED   FAILED   AGE
layered-image-a5457b883f5239cdcb71b57e1a30b6ef   False      False      True        False         False    4d17h
layered-image-f91f0f5593dd337d89bf4d38c877590b   False      True       False       False         False    2m41s

1: The value True in the BUILDING column indicates that the MachineOSBuild object is building. When the SUCCEEDED column reports True, the build is complete.

You can watch as the new machine config is rolled out to the nodes by using the following command:

$ oc get machineconfigpools

Example output

NAME      CONFIG                                              UPDATED   UPDATING   DEGRADED   MACHINECOUNT   READYMACHINECOUNT   UPDATEDMACHINECOUNT   DEGRADEDMACHINECOUNT   AGE
master    rendered-master-a0b404d061a6183cc36d302363422aba    True      False      False      3              3                   3                     0                      3h38m
worker    rendered-worker-221507009cbcdec0eec8ab3ccd789d18    False     True       False      2              2                   2                     0                      3h38m

1: The value FALSE in the UPDATED column indicates that the MachineOSBuild object is building. When the UPDATED column reports FALSE, the new custom layered image has rolled out to the nodes.

When the node is back in the Ready state, check that the changes were applied:
1. Open an oc debug session to the node by running the following command:
  $ oc debug node/<node_name>
2. Set /host as the root directory within the debug shell by running the following command:
  sh-5.1# chroot /host
3. Use an appropriate command to verify that change was applied. The following examples shows that the rngd daemon was installed:
  sh-5.1# rpm -qa |grep rng-tools
  Example output
  rng-tools-6.17-3.fc41.x86_64
  sh-5.1# rngd -v
  Example output
  rngd 6.16

Additional resources

Pausing the machine config pools

8.3.4. Rebuilding an on-cluster custom layered image
Copia collegamento

In situations where you want to rebuild an on-cluster custom layered image, you can either modify your MachineOSConfig object or add an annotation to the MachineOSConfig object. Both of these actions trigger an automatic rebuild of the object. For example, you could perform a rebuild if the you change the Containerfile or need to update the osimageurl location in a machine config.

After you add the annotation, the Machine Config Operator (MCO) deletes the current MachineOSBuild object and creates a new one in its place. When the build process is complete, the MCO automatically removes the annotation.

Prerequisites

You have opted-in to on-cluster image mode by creating a MachineOSConfig object.

Procedure

Edit the MachineOSConfig object to add the machineconfiguration.openshift.io/rebuild annotation by using the following command:

$ oc edit MachineOSConfig <object_name>

Example MachineOSConfig object

apiVersion: machineconfiguration.openshift.io/v1
kind: MachineOSConfig
metadata:
  annotations:
    machineconfiguration.openshift.io/current-machine-os-build: layering-c26d4a003432df70ee66c83981144cfa
    machineconfiguration.openshift.io/rebuild: ""


# ...
  name: layered-image
# ...

1: Add this annotation to trigger a rebuild of the custom layered image.

Verification

Check that the MachineOSBuild object is building by using the following command:

$ oc get machineosbuild

Example output

NAME                                             PREPARED   BUILDING   SUCCEEDED   INTERRUPTED   FAILED   AGE
layered-image-d6b929a29c6dbfa8e4007c8069a2fd08   False      True       False       False         False    2m41s

1: The value True in the BUILDING column indicates that the MachineOSBuild object is building.

Edit the MachineOSConfig object to verify that the MCO removed the machineconfiguration.openshift.io/rebuild annotation by using the following command:

$ oc edit MachineOSConfig <object_name>

Example MachineOSConfig object

apiVersion: machineconfiguration.openshift.io/v1
kind: MachineOSConfig
metadata:
  annotations:
    machineconfiguration.openshift.io/current-machine-os-build: layering-c26d4a003432df70ee66c83981144cfa
# ...
  name: layered-image
# ...

8.3.5. Reverting an on-cluster custom layered image
Copia collegamento

If you applied an on-cluster layered image to a node in a custom machine config pool (MCP), you can remove the custom layered image from the node and revert to the base image.

To revert the node, remove the node from the custom MCP by removing the custom machine config pool label from the node. After you remove the label, the Machine Config Operator (MCO) reboots the node with the cluster base Red Hat Enterprise Linux CoreOS (RHCOS) image, overriding the custom layered image.

Important

Before you remove the label, make sure the node is associated with another MCP.

Prerequisites

You have opted-in to On-cluster image mode by creating a MachineOSConfig object.
You have applied a MachineOSConfig object to a node in a custom machine config pool.

Procedure

Remove the label from the node by using the following command:
```
$ oc label node/<node_name> node-role.kubernetes.io/<mcp_name>-
```
When you save the changes, the MCO drains, cordons, and reboots the nodes. After the reboot, the node uses the cluster base Red Hat Enterprise Linux CoreOS (RHCOS) image.

Verification

Verify that the custom layered image is removed by performing any of the following checks:

Check that the worker machine config pool is updating with the previous machine config:

$ oc get mcp

Sample output

NAME      CONFIG                                              UPDATED   UPDATING   DEGRADED   MACHINECOUNT   READYMACHINECOUNT   UPDATEDMACHINECOUNT   DEGRADEDMACHINECOUNT   AGE
layered   rendered-layered-e8c8bc1de69777325003e80bc0c04b82   True      False      False      0              0                   0                     0                      4h20m


master    rendered-master-50d7bc27ee8b9ca2250383f0647ade7f    True      False      False      3              3                   3                     0                      5h39m
worker    rendered-worker-e8c8bc1de69777325003e80bc0c04b82    True      False      False      3              3                   3                     0                      5h39m

1: The custom machine config pool no longer has any nodes.
2: When the UPDATING field is True, the machine config pool is updating with the previous machine config. When the field becomes False, the worker machine config pool has rolled out to the previous machine config.

Check the nodes to see that scheduling on the nodes is disabled. This indicates that the change is being applied:

$ oc get nodes

Example output

NAME                                         STATUS                     ROLES                  AGE   VERSION
ip-10-0-148-79.us-west-1.compute.internal    Ready                      worker                 32m   v1.34.2
ip-10-0-155-125.us-west-1.compute.internal   Ready,SchedulingDisabled   worker                 35m   v1.34.2
ip-10-0-170-47.us-west-1.compute.internal    Ready                      control-plane,master   42m   v1.34.2
ip-10-0-174-77.us-west-1.compute.internal    Ready                      control-plane,master   42m   v1.34.2
ip-10-0-211-49.us-west-1.compute.internal    Ready                      control-plane,master   42m   v1.34.2
ip-10-0-218-151.us-west-1.compute.internal   Ready                      worker                 31m   v1.34.2

When the node is back in the Ready state, check that the node is using the base image:

Open an oc debug session to the node. For example:

$ oc debug node/ip-10-0-155-125.us-west-1.compute.internal

Set /host as the root directory within the debug shell:
```
sh-4.4# chroot /host
```

Run the rpm-ostree status command to view that the base image is in use:

sh-4.4# rpm-ostree status

Example output

State: idle
Deployments:
* ostree-unverified-registry:registry.build05.ci.openshift.org/ci-ln-qd0hmqk/stable@sha256:a8bd32573f787f6d1c23e1d669abbefd1e31339826d06e750c0ca632ad6c414f
                   Digest: sha256:a8bd32573f787f6d1c23e1d669abbefd1e31339826d06e750c0ca632ad6c414f
                  Version: 419.96.202501202201-0 (2025-01-20T22:06:13Z)

8.3.6. Removing an on-cluster custom layered image
Copia collegamento

To prevent the custom layered images from taking up excessive space in your registry, you can automatically remove an on-cluster custom layered image from the repository by deleting the MachineOSBuild object that created the image.

The credentials provided by the registry push secret that you added to the MachineOSBuild object must grant the permission for deleting an image from the registry. If the delete permission is not provided, the image is not removed when you delete the MachineOSBuild object.

The custom layered image is not deleted if the image is either currently in use on a node or is desired by the nodes, as indicated by the machineconfiguration.openshift.io/currentImage or machineconfiguration.openshift.io/desiredImage annotations on the node, which are added to the node when you create the MachineOSConfig object.

8.4. Using Out-of-cluster image mode to apply a custom layered image
Copia collegamento

You can use the image mode for OpenShift out-of-cluster build process to apply a custom layered image to your nodes by creating a MachineOSConfig custom resource (CR).

When you create the object, the Machine Config Operator (MCO) reboots those nodes with the new custom layered image, overriding the base Red Hat Enterprise Linux CoreOS (RHCOS) image.

To apply a custom layered image to your cluster, you must have the custom layered image in a repository that your cluster can access. Then, create a MachineConfig object that points to the custom layered image. You need a separate MachineConfig object for each machine config pool that you want to configure.

Important

As soon as you apply an out-of-cluster custom image to your cluster, you effectively take ownership of your custom layered images and those nodes. OpenShift Container Platform no longer automatically updates any node that uses the custom layered image. You become responsible for maintaining and updating your nodes as appropriate. If you roll back the custom layer, OpenShift Container Platform resumes automatically updating the node. See the "Updating with a RHCOS custom layered image" for important information about updating nodes that use a custom layered image.

Prerequisites

You must create a custom layered image that is based on an OpenShift Container Platform image digest, not a tag.
Note
You should use the same base RHCOS image that is installed on the rest of your cluster. Use the oc adm release info --image-for rhel-coreos command to obtain the base image being used in your cluster.
For example, the following Containerfile creates a custom layered image from an OpenShift Container Platform 4.21 image and overrides the kernel package with one from CentOS 9 Stream:
Example Containerfile for a custom layer image
```
# Using a 4.21.0 image
FROM quay.io/openshift-release-dev/ocp-v4.0-art-dev@sha256... 
```
1
```
#Install hotfix rpm
RUN rpm-ostree override replace http://mirror.stream.centos.org/9-stream/BaseOS/x86_64/os/Packages/kernel-{,core-,modules-,modules-core-,modules-extra-}5.14.0-295.el9.x86_64.rpm && \ 
```
2
```
    rpm-ostree cleanup -m && \
    bootc container lint
```
1
Specifies the RHCOS base image of your cluster.
2
Replaces the kernel packages.
Note
Instructions on how to create a Containerfile are beyond the scope of this documentation.
Because the process for building a custom layered image is performed outside of the cluster, you must use the --authfile /path/to/pull-secret option with Podman or Buildah. Alternatively, to have the pull secret read by these tools automatically, you can add it to one of the default file locations: ~/.docker/config.json, $XDG_RUNTIME_DIR/containers/auth.json, ~/.docker/config.json, or ~/.dockercfg. Refer to the containers-auth.json man page for more information.
You must push the custom layered image to a repository that your cluster can access.

Procedure

Create a machine config file.
1. Create a YAML file similar to the following:
  apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfig metadata: labels: machineconfiguration.openshift.io/role: worker
  1
  name: os-layer-custom spec: osImageURL: quay.io/my-registry/custom-image@sha256...
  2
  1
  Specifies the machine config pool to deploy the custom layered image.
  2
  Specifies the path to the custom layered image in the repository.
2. Create the MachineConfig object:
  $ oc create -f <file_name>.yaml
  Important
  It is strongly recommended that you test your images outside of your production environment before rolling out to your cluster.

Verification

You can verify that the custom layered image is applied by performing any of the following checks:

Check that the worker machine config pool has rolled out with the new machine config:

Check that the new machine config is created:

$ oc get mc

Sample output

NAME                                               GENERATEDBYCONTROLLER                      IGNITIONVERSION   AGE
00-master                                          5bdb57489b720096ef912f738b46330a8f577803   3.5.0             95m
00-worker                                          5bdb57489b720096ef912f738b46330a8f577803   3.5.0             95m
01-master-container-runtime                        5bdb57489b720096ef912f738b46330a8f577803   3.5.0             95m
01-master-kubelet                                  5bdb57489b720096ef912f738b46330a8f577803   3.5.0             95m
01-worker-container-runtime                        5bdb57489b720096ef912f738b46330a8f577803   3.5.0             95m
01-worker-kubelet                                  5bdb57489b720096ef912f738b46330a8f577803   3.5.0             95m
99-master-generated-registries                     5bdb57489b720096ef912f738b46330a8f577803   3.5.0             95m
99-master-ssh                                                                                 3.2.0             98m
99-worker-generated-registries                     5bdb57489b720096ef912f738b46330a8f577803   3.5.0             95m
99-worker-ssh                                                                                 3.2.0             98m
os-layer-custom                                                                                                 10s


rendered-master-15961f1da260f7be141006404d17d39b   5bdb57489b720096ef912f738b46330a8f577803   3.5.0             95m
rendered-worker-5aff604cb1381a4fe07feaf1595a797e   5bdb57489b720096ef912f738b46330a8f577803   3.5.0             95m
rendered-worker-5de4837625b1cbc237de6b22bc0bc873   5bdb57489b720096ef912f738b46330a8f577803   3.5.0             4s

1: New machine config
2: New rendered machine config

Check that the osImageURL value in the new machine config points to the expected image:

$ oc describe mc rendered-worker-5de4837625b1cbc237de6b22bc0bc873

Example output

Name:         rendered-worker-5de4837625b1cbc237de6b22bc0bc873
Namespace:
Labels:       <none>
Annotations:  machineconfiguration.openshift.io/generated-by-controller-version: 5bdb57489b720096ef912f738b46330a8f577803
              machineconfiguration.openshift.io/release-image-version: 4.21.0-ec.3
API Version:  machineconfiguration.openshift.io/v1
Kind:         MachineConfig
...
  Os Image URL: quay.io/my-registry/custom-image@sha256...

Check that the associated machine config pool is updated with the new machine config:

$ oc get mcp

Sample output

NAME     CONFIG                                             UPDATED   UPDATING   DEGRADED   MACHINECOUNT   READYMACHINECOUNT   UPDATEDMACHINECOUNT   DEGRADEDMACHINECOUNT   AGE
master   rendered-master-15961f1da260f7be141006404d17d39b   True      False      False      3              3                   3                     0                      39m
worker   rendered-worker-5de4837625b1cbc237de6b22bc0bc873   True      False      False      3              0                   0                     0                      39m

1: When the UPDATING field is True, the machine config pool is updating with the new machine config. In this case, you will not see the new machine config listed in the output. When the field becomes False, the worker machine config pool has rolled out to the new machine config.

Check the nodes to see that scheduling on the nodes is disabled. This indicates that the change is being applied:

$ oc get nodes

Example output

NAME                                         STATUS                     ROLES                  AGE   VERSION
ip-10-0-148-79.us-west-1.compute.internal    Ready                      worker                 32m   v1.34.2
ip-10-0-155-125.us-west-1.compute.internal   Ready,SchedulingDisabled   worker                 35m   v1.34.2
ip-10-0-170-47.us-west-1.compute.internal    Ready                      control-plane,master   42m   v1.34.2
ip-10-0-174-77.us-west-1.compute.internal    Ready                      control-plane,master   42m   v1.34.2
ip-10-0-211-49.us-west-1.compute.internal    Ready                      control-plane,master   42m   v1.34.2
ip-10-0-218-151.us-west-1.compute.internal   Ready                      worker                 31m   v1.34.2

When the node is back in the Ready state, check that the node is using the custom layered image:
1. Open an oc debug session to the node. For example:
  $ oc debug node/ip-10-0-155-125.us-west-1.compute.internal
2. Set /host as the root directory within the debug shell:
  sh-4.4# chroot /host
3. Run the rpm-ostree status command to view that the custom layered image is in use:
  sh-4.4# sudo rpm-ostree status
  Example output
  State: idle Deployments: * ostree-unverified-registry:quay.io/my-registry/... Digest: sha256:...

Additional resources

Updating with a RHCOS custom layered image

8.4.1. Reverting an out-of-cluster node
Copia collegamento

You can revert an out-of-cluster custom layered image from the nodes in specific machine config pools. The Machine Config Operator (MCO) reboots those nodes with the cluster base Red Hat Enterprise Linux CoreOS (RHCOS) image, overriding the custom layered image.

To remove a Red Hat Enterprise Linux CoreOS (RHCOS) custom layered image from your cluster, you need to delete the machine config that applied the image.

Procedure

Delete the machine config that applied the custom layered image.
```
$ oc delete mc os-layer-custom
```
After deleting the machine config, the nodes reboot.

Verification

You can verify that the custom layered image is removed by performing any of the following checks:

Check that the worker machine config pool is updating with the previous machine config:

$ oc get mcp

Sample output

NAME     CONFIG                                             UPDATED   UPDATING   DEGRADED   MACHINECOUNT   READYMACHINECOUNT   UPDATEDMACHINECOUNT   DEGRADEDMACHINECOUNT   AGE
master   rendered-master-6faecdfa1b25c114a58cf178fbaa45e2   True      False      False      3              3                   3                     0                      39m
worker   rendered-worker-6b000dbc31aaee63c6a2d56d04cd4c1b   False     True       False      3              0                   0                     0                      39m

1: When the UPDATING field is True, the machine config pool is updating with the previous machine config. When the field becomes False, the worker machine config pool has rolled out to the previous machine config.

Check the nodes to see that scheduling on the nodes is disabled. This indicates that the change is being applied:

$ oc get nodes

Example output

NAME                                         STATUS                     ROLES                  AGE   VERSION
ip-10-0-148-79.us-west-1.compute.internal    Ready                      worker                 32m   v1.34.2
ip-10-0-155-125.us-west-1.compute.internal   Ready,SchedulingDisabled   worker                 35m   v1.34.2
ip-10-0-170-47.us-west-1.compute.internal    Ready                      control-plane,master   42m   v1.34.2
ip-10-0-174-77.us-west-1.compute.internal    Ready                      control-plane,master   42m   v1.34.2
ip-10-0-211-49.us-west-1.compute.internal    Ready                      control-plane,master   42m   v1.34.2
ip-10-0-218-151.us-west-1.compute.internal   Ready                      worker                 31m   v1.34.2

When the node is back in the Ready state, check that the node is using the base image:

Open an oc debug session to the node by running the following command:
```
$ oc debug node/<node_name>
```
Set /host as the root directory within the debug shell by running the following command:
```
sh-5.1# chroot /host
```

Run the rpm-ostree status command to view that the custom layered image is in use:

sh-5.1# sudo rpm-ostree status

Example output

State: idle
Deployments:
* ostree-unverified-registry:podman pull quay.io/openshift-release-dev/ocp-release@sha256:e2044c3cfebe0ff3a99fc207ac5efe6e07878ad59fd4ad5e41f88cb016dacd73
                   Digest: sha256:e2044c3cfebe0ff3a99fc207ac5efe6e07878ad59fd4ad5e41f88cb016dacd73

8.5. Applying a custom layered image during OpenShift Container Platform installation
Copia collegamento

You can use the standard OpenShift Container Platform installation process to apply a custom layered image to your nodes by adding a MachineOSConfig custom resource (CR) YAML and a push secret YAML to the <installation_directory>/manifests/ directory. This allows you to use image mode for OpenShift to apply additional functionality to specific nodes upon cluster installation.

After the installation, if you modify a machine config pool or update the OpenShift Container Platform version, the Machine Config Operator (MCO) builds and applies a new custom layered image, and pushes the updated image to your repository.

Prerequisites

You have a custom layered image in a repository that your cluster can access.

Example containerFile for a custom layered image

FROM quay.io/centos/centos:stream9 AS centos
RUN dnf install -y epel-release

FROM [rhel-coreos image] AS configs
COPY --from=centos /etc/yum.repos.d /etc/yum.repos.d
COPY --from=centos /etc/pki/rpm-gpg/RPM-GPG-KEY-* /etc/pki/rpm-gpg/
RUN sed -i 's/\$stream/9-stream/g' /etc/yum.repos.d/centos*.repo && \
    rpm-ostree install cowsay && \
    ostree container commit

You have a repository and any needed secret where the MCO can push any updated custom layered images.

Procedure

Create a YAML file for the MachineOSConfig object similar to the following:
```
apiVersion: machineconfiguration.openshift.io/v1
kind: MachineOSConfig
metadata:
  name: worker
  annotations:
    machineconfiguration.openshift.io/pre-built-image: "quay.io/myorg/custom-rhcos@sha256:abc123..."
spec:
  machineConfigPool:
    name: worker
  imageBuilder:
    imageBuilderType: Job
  renderedImagePushSpec: quay.io/your-registry/layered-rhcos:latest
  renderedImagePushSecret:
    name: push-secret
  containerFile:
  - containerfileArch: NoArch
    content: |
      FROM configs AS final
      RUN rpm-ostree install cowsay && \
        ostree container commit
```
where:
metadata.name
Specifies a name for the MachineOSConfig object. The name must match the name of the associated machine config pool.
metadata.annotations.machineconfiguration.openshift.io/pre-built-image
Specifies the digested image pull spec of your custom layered image.
spec.machineConfigPool
Specifies the name of the machine config pool associated with the nodes where you want to deploy the custom layered image.
spec.imageBuilder.imageBuilderType
Specifies the name of the image builder to use. This must be Job, which is a reference to the job object that is managing the image build.
spec.renderedImagePushSpec
Specifies an image registry to push any updated custom layered images to, if needed, after the installation process is complete. This can be any registry that your cluster has access to in the host[:port][/namespace]/name or svc_name.namespace.svc[:port]/repository/name:<tag> format. You can specify a mirror registry if you cluster is properly configured to use a mirror registry.
spec.renderedImagePushSecret.name
Specifies the name of the push secret needed by the MCO to push the updated custom layered image to that registry.
spec.containerFile
Specifies the containerFile that you used to create the custom layered image.

Create a YAML file for the push secret similar to the following:

apiVersion: v1
kind: Secret
metadata:
  name: push-secret
  namespace: openshift-machine-config-operator
data:
  .dockerconfigjson: secret
type: kubernetes.io/dockerconfigjson

When the manifests directory is available, add the MachineOSConfig YAML to the directory by using a command similar to the following:
```
$ cp <file-name>.yaml manifests/
```
where:
file-name
Specifies the YAML file for the MachineOSConfig object.
Add the push secret YAML to the manifests directory by using a command similar to the following:
```
$ cp <file-name>.yaml manifests/
```
where:
file-name
Specifies the YAML file for the push secret.
Continue with the installation process as usual.

Verification

After the installation is complete, check that the MachineOSConfig object displays the PreBuiltImageSeeded status as True and contains a reference to the custom layered image by using the following command:

$ oc get machineosconfigs.machineconfiguration.openshift.io -o yaml

Example output

apiVersion: v1
items:
- apiVersion: machineconfiguration.openshift.io/v1
  kind: MachineOSConfig
  metadata:
    annotations:
      machineconfiguration.openshift.io/current-machine-os-build: worker-4cedbc10da849ae7019288febc3a2d17
# ...
  status:
    conditions:
    - lastTransitionTime: "2025-11-19T13:32:17Z"
      message: MachineOSConfig seeded with pre-built image "quay.io/myorg/custom-rhcos@sha256:abc123..."
      reason: PreBuiltImageSeeded
      status: "True"
      type: Seeded
    currentImagePullSpec: image-registry.openshift-image-registry.svc:5000/openshift-machine-config-operator/layered-rhcos@sha256:3c8fc667adcb432ce0c83581f16086afec08a961dd28fed69bb6bad6db0a0754

where:

items.status.conditions.reason.PreBuiltImageSeeded.True: Specifies that the associated nodes were created using your custom layered image.
items.status.currentImagePullSpec: Specifies the digested image pull spec for the new custom layered image.

8.6. Updating with a RHCOS custom layered image
Copia collegamento

When you configure image mode for OpenShift, OpenShift Container Platform no longer automatically updates the node pool that uses the custom layered image. You become responsible to manually update your nodes as appropriate.

To update a node that uses a custom layered image, follow these general steps:

The cluster automatically upgrades to version x.y.z+1, except for the nodes that use the custom layered image.
You could then create a new Containerfile that references the updated OpenShift Container Platform image and the RPM that you had previously applied.
Create a new machine config that points to the updated custom layered image.

Updating a node with a custom layered image is not required. However, if that node gets too far behind the current OpenShift Container Platform version, you could experience unexpected results.

Questo contenuto non è disponibile nella lingua selezionata.

Chapter 8. Image mode for OpenShift

8.1. About image mode for OpenShift
Copia collegamento

8.2. Example Containerfiles
Copia collegamento

8.3. About on-cluster image mode
Copia collegamento

8.3.1. On-cluster image mode known limitations
Copia collegamento

8.3.2. Using the on-cluster image mode to apply a custom layered image
Copia collegamento

8.3.3. Modifying an on-cluster custom layered image
Copia collegamento

8.3.4. Rebuilding an on-cluster custom layered image
Copia collegamento

8.3.5. Reverting an on-cluster custom layered image
Copia collegamento

8.3.6. Removing an on-cluster custom layered image
Copia collegamento

8.4. Using Out-of-cluster image mode to apply a custom layered image
Copia collegamento

8.4.1. Reverting an out-of-cluster node
Copia collegamento

8.5. Applying a custom layered image during OpenShift Container Platform installation
Copia collegamento

8.6. Updating with a RHCOS custom layered image
Copia collegamento

Formazione

Prova, acquista e vendi

Community

Informazioni sulla documentazione di Red Hat

Rendiamo l’open source più inclusivo

Informazioni su Red Hat

Theme

Red Hat legal and privacy links

Red Hat legal and privacy links

Questo contenuto non è disponibile nella lingua selezionata.

Chapter 8. Image mode for OpenShift

8.1. About image mode for OpenShiftCopia collegamentoCollegamento copiato negli appunti!

8.2. Example ContainerfilesCopia collegamentoCollegamento copiato negli appunti!

8.3. About on-cluster image modeCopia collegamentoCollegamento copiato negli appunti!

8.3.1. On-cluster image mode known limitationsCopia collegamentoCollegamento copiato negli appunti!

8.3.2. Using the on-cluster image mode to apply a custom layered imageCopia collegamentoCollegamento copiato negli appunti!

8.3.3. Modifying an on-cluster custom layered imageCopia collegamentoCollegamento copiato negli appunti!

8.3.4. Rebuilding an on-cluster custom layered imageCopia collegamentoCollegamento copiato negli appunti!

8.3.5. Reverting an on-cluster custom layered imageCopia collegamentoCollegamento copiato negli appunti!

8.3.6. Removing an on-cluster custom layered imageCopia collegamentoCollegamento copiato negli appunti!

8.4. Using Out-of-cluster image mode to apply a custom layered imageCopia collegamentoCollegamento copiato negli appunti!

8.4.1. Reverting an out-of-cluster nodeCopia collegamentoCollegamento copiato negli appunti!

8.5. Applying a custom layered image during OpenShift Container Platform installationCopia collegamentoCollegamento copiato negli appunti!

8.6. Updating with a RHCOS custom layered imageCopia collegamentoCollegamento copiato negli appunti!

Formazione

Prova, acquista e vendi

Community

Informazioni sulla documentazione di Red Hat

Rendiamo l’open source più inclusivo

Informazioni su Red Hat

Theme

Red Hat legal and privacy links

Red Hat legal and privacy links

8.1. About image mode for OpenShift
Copia collegamento

8.2. Example Containerfiles
Copia collegamento

8.3. About on-cluster image mode
Copia collegamento

8.3.1. On-cluster image mode known limitations
Copia collegamento

8.3.2. Using the on-cluster image mode to apply a custom layered image
Copia collegamento

8.3.3. Modifying an on-cluster custom layered image
Copia collegamento

8.3.4. Rebuilding an on-cluster custom layered image
Copia collegamento

8.3.5. Reverting an on-cluster custom layered image
Copia collegamento

8.3.6. Removing an on-cluster custom layered image
Copia collegamento

8.4. Using Out-of-cluster image mode to apply a custom layered image
Copia collegamento

8.4.1. Reverting an out-of-cluster node
Copia collegamento

8.5. Applying a custom layered image during OpenShift Container Platform installation
Copia collegamento

8.6. Updating with a RHCOS custom layered image
Copia collegamento