Chapter 5. Enabling Windows container workloads
Chapter 5. Enabling Windows container workloads Before adding Windows workloads to your cluster, you must install the Windows Machine Config Operator (WMCO), which is available in the OpenShift Container Platform OperatorHub. The WMCO orchestrates the process of deploying and managing Windows workloads on a cluster. Note Dual NIC is not supported on WMCO-managed Windows instances. Prerequisites You have access to an OpenShift Container Platform cluster using an account with cluster-admin permissions. You have installed the OpenShift CLI ( oc ). You have installed your cluster using installer-provisioned infrastructure, or using user-provisioned infrastructure with the platform: none field set in your install-config.yaml file. You have configured hybrid networking with OVN-Kubernetes for your cluster. For more information, see Configuring hybrid networking . You are running an OpenShift Container Platform cluster version 4.6.8 or later. Note Windows instances deployed by the WMCO are configured with the containerd container runtime. Because WMCO installs and manages the runtime, it is recommended that you do not manually install containerd on nodes. Additional resources For the comprehensive prerequisites for the Windows Machine Config Operator, see Windows Machine Config Operator prerequisites . 5.1. Installing the Windows Machine Config Operator You can install the Windows Machine Config Operator using either the web console or OpenShift CLI ( oc ). Note Due to a limitation within the Windows operating system, clusterNetwork CIDR addresses of class E, such as 240.0.0.0 , are not compatible with Windows nodes. 5.1.1. Installing the Windows Machine Config Operator using the web console You can use the OpenShift Container Platform web console to install the Windows Machine Config Operator (WMCO). Note Dual NIC is not supported on WMCO-managed Windows instances. Procedure From the Administrator perspective in the OpenShift Container Platform web console, navigate to the Operators OperatorHub page. Use the Filter by keyword box to search for Windows Machine Config Operator in the catalog. Click the Windows Machine Config Operator tile. Review the information about the Operator and click Install . On the Install Operator page: Select the stable channel as the Update Channel . The stable channel enables the latest stable release of the WMCO to be installed. The Installation Mode is preconfigured because the WMCO must be available in a single namespace only. Choose the Installed Namespace for the WMCO. The default Operator recommended namespace is openshift-windows-machine-config-operator . Click the Enable Operator recommended cluster monitoring on the Namespace checkbox to enable cluster monitoring for the WMCO. Select an Approval Strategy . The Automatic strategy allows Operator Lifecycle Manager (OLM) to automatically update the Operator when a new version is available. The Manual strategy requires a user with appropriate credentials to approve the Operator update. Click Install . The WMCO is now listed on the Installed Operators page. Note The WMCO is installed automatically into the namespace you defined, like openshift-windows-machine-config-operator . Verify that the Status shows Succeeded to confirm successful installation of the WMCO. 5.1.2. Installing the Windows Machine Config Operator using the CLI You can use the OpenShift CLI ( oc ) to install the Windows Machine Config Operator (WMCO). Note Dual NIC is not supported on WMCO-managed Windows instances. Procedure Create a namespace for the WMCO. Create a Namespace object YAML file for the WMCO. For example, wmco-namespace.yaml : apiVersion: v1 kind: Namespace metadata: name: openshift-windows-machine-config-operator 1 labels: openshift.io/cluster-monitoring: "true" 2 1 It is recommended to deploy the WMCO in the openshift-windows-machine-config-operator namespace. 2 This label is required for enabling cluster monitoring for the WMCO. Create the namespace: USD oc create -f <file-name>.yaml For example: USD oc create -f wmco-namespace.yaml Create the Operator group for the WMCO. Create an OperatorGroup object YAML file. For example, wmco-og.yaml : apiVersion: operators.coreos.com/v1 kind: OperatorGroup metadata: name: windows-machine-config-operator namespace: openshift-windows-machine-config-operator spec: targetNamespaces: - openshift-windows-machine-config-operator Create the Operator group: USD oc create -f <file-name>.yaml For example: USD oc create -f wmco-og.yaml Subscribe the namespace to the WMCO. Create a Subscription object YAML file. For example, wmco-sub.yaml : apiVersion: operators.coreos.com/v1alpha1 kind: Subscription metadata: name: windows-machine-config-operator namespace: openshift-windows-machine-config-operator spec: channel: "stable" 1 installPlanApproval: "Automatic" 2 name: "windows-machine-config-operator" source: "redhat-operators" 3 sourceNamespace: "openshift-marketplace" 4 1 Specify stable as the channel. 2 Set an approval strategy. You can set Automatic or Manual . 3 Specify the redhat-operators catalog source, which contains the windows-machine-config-operator package manifests. If your OpenShift Container Platform is installed on a restricted network, also known as a disconnected cluster, specify the name of the CatalogSource object you created when you configured the Operator LifeCycle Manager (OLM). 4 Namespace of the catalog source. Use openshift-marketplace for the default OperatorHub catalog sources. Create the subscription: USD oc create -f <file-name>.yaml For example: USD oc create -f wmco-sub.yaml The WMCO is now installed to the openshift-windows-machine-config-operator . Verify the WMCO installation: USD oc get csv -n openshift-windows-machine-config-operator Example output NAME DISPLAY VERSION REPLACES PHASE windows-machine-config-operator.2.0.0 Windows Machine Config Operator 2.0.0 Succeeded 5.2. Configuring a secret for the Windows Machine Config Operator To run the Windows Machine Config Operator (WMCO), you must create a secret in the WMCO namespace containing a private key. This is required to allow the WMCO to communicate with the Windows virtual machine (VM). Prerequisites You installed the Windows Machine Config Operator (WMCO) using Operator Lifecycle Manager (OLM). You created a PEM-encoded file containing an RSA key. Procedure Define the secret required to access the Windows VMs: USD oc create secret generic cloud-private-key --from-file=private-key.pem=USD{HOME}/.ssh/<key> \ -n openshift-windows-machine-config-operator 1 1 You must create the private key in the WMCO namespace, like openshift-windows-machine-config-operator . It is recommended to use a different private key than the one used when installing the cluster. 5.3. Using Windows containers in a proxy-enabled cluster The Windows Machine Config Operator (WMCO) can consume and use a cluster-wide egress proxy configuration when making external requests outside the cluster's internal network. This allows you to add Windows nodes and run workloads in a proxy-enabled cluster, allowing your Windows nodes to pull images from registries that are secured behind your proxy server or to make requests to off-cluster services and services that use a custom public key infrastructure. Note The cluster-wide proxy affects system components only, not user workloads. In proxy-enabled clusters, the WMCO is aware of the NO_PROXY , HTTP_PROXY , and HTTPS_PROXY values that are set for the cluster. The WMCO periodically checks whether the proxy environment variables have changed. If there is a discrepancy, the WMCO reconciles and updates the proxy environment variables on the Windows instances. Windows workloads created on Windows nodes in proxy-enabled clusters do not inherit proxy settings from the node by default, the same as with Linux nodes. Also, by default PowerShell sessions do not inherit proxy settings on Windows nodes in proxy-enabled clusters. Additional resources Configuring the cluster-wide proxy . 5.4. Using Windows containers with a mirror registry The Windows Machine Config Operator (WMCO) can pull images from a registry mirror rather than from a public registry by using an ImageDigestMirrorSet (IDMS) or ImageTagMirrorSet (ITMS) object to configure your cluster to pull images from the mirror registry. A mirror registry has the following benefits: Avoids public registry outages Speeds up node and pod creation Pulls images from behind your organization's firewall A mirror registry can also be used with a OpenShift Container Platform cluster in a disconnected, or air-gapped, network. A disconnected network is a restricted network without direct internet connectivity. Because the cluster does not have access to the internet, any external container images cannot be referenced. Using a mirror registry requires the following general steps: Create the mirror registry, using a tool such as Red Hat Quay. Create a container image registry credentials file. Copy the images from your online image repository to your mirror registry. For information about these steps, see "About disconnected installation mirroring." After creating the mirror registry and mirroring the images, you can use an ImageDigestMirrorSet (IDMS) or ImageTagMirrorSet (ITMS) object to configure your cluster to pull images from the mirror registry without needing to update each of your pod specs. The IDMS and ITMS objects redirect requests to pull images from a repository on a source image registry and have it resolved by the mirror repository instead. If changes are made to the IDMS or ITMS object, the WMCO automatically updates the appropriate hosts.toml file on your Windows nodes with the new information. Note that the WMCO sequentially updates each Windows node when mirror settings are changed. As such, the time required for these updates increases with the number of Windows nodes in the cluster. Also, because Windows nodes configured by the WMCO rely on containerd container runtime, the WMCO ensures that the containerd config files are up-to-date with the registry settings. For new nodes, these files are copied to the instances upon creation. For existing nodes, after activating the mirror registry, the registry controller uses SSH to access each node and copy the generated config files, replacing any existing files. You can use a mirror registry with machine set or Bring-Your-Own-Host (BYOH) Windows nodes. Additional resources About disconnected installation mirroring 5.4.1. Understanding image registry repository mirroring Setting up container registry repository mirroring enables you to perform the following tasks: Configure your OpenShift Container Platform cluster to redirect requests to pull images from a repository on a source image registry and have it resolved by a repository on a mirrored image registry. Identify multiple mirrored repositories for each target repository, to make sure that if one mirror is down, another can be used. Repository mirroring in OpenShift Container Platform includes the following attributes: Image pulls are resilient to registry downtimes. Clusters in disconnected environments can pull images from critical locations, such as quay.io, and have registries behind a company firewall provide the requested images. A particular order of registries is tried when an image pull request is made, with the permanent registry typically being the last one tried. The mirror information you enter is added to the appropriate hosts.toml containerd configuration file(s) on every Windows node in the OpenShift Container Platform cluster. When a node makes a request for an image from the source repository, it tries each mirrored repository in turn until it finds the requested content. If all mirrors fail, the cluster tries the source repository. If successful, the image is pulled to the node. Setting up repository mirroring can be done in the following ways: At OpenShift Container Platform installation: By pulling container images needed by OpenShift Container Platform and then bringing those images behind your company's firewall, you can install OpenShift Container Platform into a data center that is in a disconnected environment. After OpenShift Container Platform installation: If you did not configure mirroring during OpenShift Container Platform installation, you can do so postinstallation by using any of the following custom resource (CR) objects: ImageDigestMirrorSet (IDMS). This object allows you to pull images from a mirrored registry by using digest specifications. The IDMS CR enables you to set a fall back policy that allows or stops continued attempts to pull from the source registry if the image pull fails. ImageTagMirrorSet (ITMS). This object allows you to pull images from a mirrored registry by using image tags. The ITMS CR enables you to set a fall back policy that allows or stops continued attempts to pull from the source registry if the image pull fails. Each of these custom resource objects identify the following information: The source of the container image repository you want to mirror. A separate entry for each mirror repository you want to offer the content requested from the source repository. The Windows Machine Config Operator (WMCO) watches for changes to the IDMS and ITMS resources and generates a set of hosts.toml containerd configuration files, one file for each source registry, with those changes. The WMCO then updates any existing Windows nodes to use the new registry configuration. Note The IDMS and ITMS objects must be created before you can add Windows nodes using a mirrored registry. 5.4.2. Configuring image registry repository mirroring You can create postinstallation mirror configuration custom resources (CR) to redirect image pull requests from a source image registry to a mirrored image registry. Important Windows images mirrored through ImageDigestMirrorSet and ImageTagMirrorSet objects have specific naming requirements. The final portion of the namespace and the image name of the mirror image must match the image being mirrored. For example, when mirroring the mcr.microsoft.com/oss/kubernetes/pause:3.9 image, the mirror image must have the <mirror_registry>/<optional_namespaces>/oss/kubernetes/pause:3.9 format. The optional_namespaces can be any number of leading repository namespaces. Prerequisites Access to the cluster as a user with the cluster-admin role. Procedure Configure mirrored repositories, by either: Setting up a mirrored repository with Red Hat Quay, as described in Red Hat Quay Repository Mirroring . Using Red Hat Quay allows you to copy images from one repository to another and also automatically sync those repositories repeatedly over time. Using a tool such as skopeo to copy images manually from the source repository to the mirrored repository. For example, after installing the skopeo RPM package on a Red Hat Enterprise Linux (RHEL) 7 or RHEL 8 system, use the skopeo command as shown in this example: USD skopeo copy --all \ docker://registry.access.redhat.com/ubi9/ubi-minimal:latest@sha256:5cf... \ docker://example.io/example/ubi-minimal In this example, you have a container image registry that is named example.io with an image repository named example to which you want to copy the ubi9/ubi-minimal image from registry.access.redhat.com . After you create the mirrored registry, you can configure your OpenShift Container Platform cluster to redirect requests made of the source repository to the mirrored repository. Important You must mirror the mcr.microsoft.com/oss/kubernetes/pause:3.9 image. For example, you could use the following skopeo command to mirror the image: USD skopeo copy \ docker://mcr.microsoft.com/oss/kubernetes/pause:3.9\ docker://example.io/oss/kubernetes/pause:3.9 Log in to your OpenShift Container Platform cluster. Create an ImageDigestMirrorSet or ImageTagMirrorSet CR, as needed, replacing the source and mirrors with your own registry and repository pairs and images: apiVersion: config.openshift.io/v1 1 kind: ImageDigestMirrorSet 2 metadata: name: ubi9repo spec: imageDigestMirrors: 3 - mirrors: - example.io/example/ubi-minimal 4 - example.com/example2/ubi-minimal 5 source: registry.access.redhat.com/ubi9/ubi-minimal 6 mirrorSourcePolicy: AllowContactingSource 7 - mirrors: - mirror.example.com source: registry.redhat.io mirrorSourcePolicy: NeverContactSource - mirrors: - docker.io source: docker-mirror.internal mirrorSourcePolicy: AllowContactingSource 1 Indicates the API to use with this CR. This must be config.openshift.io/v1 . 2 Indicates the kind of object according to the pull type: ImageDigestMirrorSet : Pulls a digest reference image. ImageTagMirrorSet : Pulls a tag reference image. 3 Indicates the type of image pull method, either: imageDigestMirrors : Use for an ImageDigestMirrorSet CR. imageTagMirrors : Use for an ImageTagMirrorSet CR. 4 Indicates the name of the mirrored image registry and repository. 5 Optional: Indicates a secondary mirror repository for each target repository. If one mirror is down, the target repository can use another mirror. 6 Indicates the registry and repository source, which is the repository that is referred to in image pull specifications. 7 Optional: Indicates the fallback policy if the image pull fails: AllowContactingSource : Allows continued attempts to pull the image from the source repository. This is the default. NeverContactSource : Prevents continued attempts to pull the image from the source repository. Create the new object: USD oc create -f registryrepomirror.yaml To check that the mirrored configuration settings are applied, do the following on one of the nodes. List your nodes: USD oc get node Example output NAME STATUS ROLES AGE VERSION ip-10-0-137-44.ec2.internal Ready worker 7m v1.29.4 ip-10-0-138-148.ec2.internal Ready master 11m v1.29.4 ip-10-0-139-122.ec2.internal Ready master 11m v1.29.4 ip-10-0-147-35.ec2.internal Ready worker 7m v1.29.4 ip-10-0-153-12.ec2.internal Ready worker 7m v1.29.4 ip-10-0-154-10.ec2.internal Ready master 11m v1.29.4 Start the debugging process to access the node: USD oc debug node/ip-10-0-147-35.ec2.internal Example output Starting pod/ip-10-0-147-35ec2internal-debug ... To use host binaries, run `chroot /host` Change your root directory to /host : sh-4.2# chroot /host Check that the WMCO generated a hosts.toml file for each registry on each Windows instance. For the example IDMS object, there should be three files in the following file structure: USD tree USDconfig_path Example output C:/k/containerd/registries/ |── registry.access.redhat.com | └── hosts.toml |── mirror.example.com | └── hosts.toml └── docker.io └── hosts.toml: The following output represents a hosts.toml containerd configuration file where the example IDMS object was applied. Example host.toml files USD cat "USDconfig_path"/registry.access.redhat.com/host.toml server = "https://registry.access.redhat.com" # default fallback server since "AllowContactingSource" mirrorSourcePolicy is set [host."https://example.io/example/ubi-minimal"] capabilities = ["pull"] [host."https://example.com/example2/ubi-minimal"] # secondary mirror capabilities = ["pull"] USD cat "USDconfig_path"/registry.redhat.io/host.toml # "server" omitted since "NeverContactSource" mirrorSourcePolicy is set [host."https://mirror.example.com"] capabilities = ["pull"] USD cat "USDconfig_path"/docker.io/host.toml server = "https://docker.io" [host."https://docker-mirror.internal"] capabilities = ["pull", "resolve"] # resolve tags Pull an image to the node from the source and check if it is resolved by the mirror. sh-4.2# podman pull --log-level=debug registry.access.redhat.com/ubi9/ubi-minimal@sha256:5cf... Troubleshooting repository mirroring If the repository mirroring procedure does not work as described, use the following information about how repository mirroring works to help troubleshoot the problem. The first working mirror is used to supply the pulled image. The main registry is only used if no other mirror works. From the system context, the Insecure flags are used as fallback. 5.5. Rebooting a node gracefully The Windows Machine Config Operator (WMCO) minimizes node reboots whenever possible. However, certain operations and updates require a reboot to ensure that changes are applied correctly and securely. To safely reboot your Windows nodes, use the graceful reboot process. For information on gracefully rebooting a standard OpenShift Container Platform node, see "Rebooting a node gracefully" in the Nodes documentation. Before rebooting a node, it is recommended to backup etcd data to avoid any data loss on the node. Note For single-node OpenShift clusters that require users to perform the oc login command rather than having the certificates in kubeconfig file to manage the cluster, the oc adm commands might not be available after cordoning and draining the node. This is because the openshift-oauth-apiserver pod is not running due to the cordon. You can use SSH to access the nodes as indicated in the following procedure. In a single-node OpenShift cluster, pods cannot be rescheduled when cordoning and draining. However, doing so gives the pods, especially your workload pods, time to properly stop and release associated resources. Procedure To perform a graceful restart of a node: Mark the node as unschedulable: USD oc adm cordon <node1> Drain the node to remove all the running pods: USD oc adm drain <node1> --ignore-daemonsets --delete-emptydir-data --force You might receive errors that pods associated with custom pod disruption budgets (PDB) cannot be evicted. Example error error when evicting pods/"rails-postgresql-example-1-72v2w" -n "rails" (will retry after 5s): Cannot evict pod as it would violate the pod's disruption budget. In this case, run the drain command again, adding the disable-eviction flag, which bypasses the PDB checks: USD oc adm drain <node1> --ignore-daemonsets --delete-emptydir-data --force --disable-eviction SSH into the Windows node and enter PowerShell by running the following command: C:\> powershell Restart the node by running the following command: C:\> Restart-Computer -Force Windows nodes on Amazon Web Services (AWS) do not return to READY state after a graceful reboot due to an inconsistency with the EC2 instance metadata routes and the Host Network Service (HNS) networks. After the reboot, SSH into any Windows node on AWS and add the route by running the following command in a shell prompt: C:\> route add 169.254.169.254 mask 255.255.255.0 <gateway_ip> where: 169.254.169.254 Specifies the address of the EC2 instance metadata endpoint. 255.255.255.255 Specifies the network mask of the EC2 instance metadata endpoint. <gateway_ip> Specifies the corresponding IP address of the gateway in the Windows instance, which you can find by running the following command: C:\> ipconfig | findstr /C:"Default Gateway" After the reboot is complete, mark the node as schedulable by running the following command: USD oc adm uncordon <node1> Verify that the node is ready: USD oc get node <node1> Example output NAME STATUS ROLES AGE VERSION <node1> Ready worker 6d22h v1.18.3+b0068a8 Additional resources Rebooting a OpenShift Container Platform node gracefully Backing up etcd data 5.6. Additional resources Generating a key pair for cluster node SSH access Adding Operators to a cluster
apiVersion: v1 kind: Namespace metadata: name: openshift-windows-machine-config-operator 1 labels: openshift.io/cluster-monitoring: "true" 2 oc create -f <file-name>.yaml oc create -f wmco-namespace.yaml apiVersion: operators.coreos.com/v1 kind: OperatorGroup metadata: name: windows-machine-config-operator namespace: openshift-windows-machine-config-operator spec: targetNamespaces: - openshift-windows-machine-config-operator oc create -f <file-name>.yaml oc create -f wmco-og.yaml apiVersion: operators.coreos.com/v1alpha1 kind: Subscription metadata: name: windows-machine-config-operator namespace: openshift-windows-machine-config-operator spec: channel: "stable" 1 installPlanApproval: "Automatic" 2 name: "windows-machine-config-operator" source: "redhat-operators" 3 sourceNamespace: "openshift-marketplace" 4 oc create -f <file-name>.yaml oc create -f wmco-sub.yaml oc get csv -n openshift-windows-machine-config-operator NAME DISPLAY VERSION REPLACES PHASE windows-machine-config-operator.2.0.0 Windows Machine Config Operator 2.0.0 Succeeded oc create secret generic cloud-private-key --from-file=private-key.pem=USD{HOME}/.ssh/<key> -n openshift-windows-machine-config-operator 1 skopeo copy --all docker://registry.access.redhat.com/ubi9/ubi-minimal:latest@sha256:5cf... docker://example.io/example/ubi-minimal skopeo copy docker://mcr.microsoft.com/oss/kubernetes/pause:3.9 docker://example.io/oss/kubernetes/pause:3.9 apiVersion: config.openshift.io/v1 1 kind: ImageDigestMirrorSet 2 metadata: name: ubi9repo spec: imageDigestMirrors: 3 - mirrors: - example.io/example/ubi-minimal 4 - example.com/example2/ubi-minimal 5 source: registry.access.redhat.com/ubi9/ubi-minimal 6 mirrorSourcePolicy: AllowContactingSource 7 - mirrors: - mirror.example.com source: registry.redhat.io mirrorSourcePolicy: NeverContactSource - mirrors: - docker.io source: docker-mirror.internal mirrorSourcePolicy: AllowContactingSource oc create -f registryrepomirror.yaml oc get node NAME STATUS ROLES AGE VERSION ip-10-0-137-44.ec2.internal Ready worker 7m v1.29.4 ip-10-0-138-148.ec2.internal Ready master 11m v1.29.4 ip-10-0-139-122.ec2.internal Ready master 11m v1.29.4 ip-10-0-147-35.ec2.internal Ready worker 7m v1.29.4 ip-10-0-153-12.ec2.internal Ready worker 7m v1.29.4 ip-10-0-154-10.ec2.internal Ready master 11m v1.29.4 oc debug node/ip-10-0-147-35.ec2.internal Starting pod/ip-10-0-147-35ec2internal-debug To use host binaries, run `chroot /host` sh-4.2# chroot /host tree USDconfig_path C:/k/containerd/registries/ |── registry.access.redhat.com | └── hosts.toml |── mirror.example.com | └── hosts.toml └── docker.io └── hosts.toml: cat "USDconfig_path"/registry.access.redhat.com/host.toml server = "https://registry.access.redhat.com" # default fallback server since "AllowContactingSource" mirrorSourcePolicy is set [host."https://example.io/example/ubi-minimal"] capabilities = ["pull"] secondary mirror capabilities = ["pull"] cat "USDconfig_path"/registry.redhat.io/host.toml "server" omitted since "NeverContactSource" mirrorSourcePolicy is set [host."https://mirror.example.com"] capabilities = ["pull"] cat "USDconfig_path"/docker.io/host.toml server = "https://docker.io" [host."https://docker-mirror.internal"] capabilities = ["pull", "resolve"] # resolve tags sh-4.2# podman pull --log-level=debug registry.access.redhat.com/ubi9/ubi-minimal@sha256:5cf oc adm cordon <node1> oc adm drain <node1> --ignore-daemonsets --delete-emptydir-data --force error when evicting pods/"rails-postgresql-example-1-72v2w" -n "rails" (will retry after 5s): Cannot evict pod as it would violate the pod's disruption budget. oc adm drain <node1> --ignore-daemonsets --delete-emptydir-data --force --disable-eviction C:\> powershell C:\> Restart-Computer -Force C:\> route add 169.254.169.254 mask 255.255.255.0 <gateway_ip> C:\> ipconfig | findstr /C:"Default Gateway" oc adm uncordon <node1> oc get node <node1> NAME STATUS ROLES AGE VERSION <node1> Ready worker 6d22h v1.18.3+b0068a8