Chapter 5. Postinstallation machine configuration tasks There are times when you need to make changes to the operating systems running on OpenShift Container Platform nodes. This can include changing settings for network time service, adding kernel arguments, or configuring journaling in a specific way. Aside from a few specialized features, most changes to operating systems on OpenShift Container Platform nodes can be done by creating what are referred to as MachineConfig objects that are managed by the Machine Config Operator. Tasks in this section describe how to use features of the Machine Config Operator to configure operating system features on OpenShift Container Platform nodes. 5.1. About the Machine Config Operator OpenShift Container Platform 4.13 integrates both operating system and cluster management. Because the cluster manages its own updates, including updates to Red Hat Enterprise Linux CoreOS (RHCOS) on cluster nodes, OpenShift Container Platform provides an opinionated lifecycle management experience that simplifies the orchestration of node upgrades. OpenShift Container Platform employs three daemon sets and controllers to simplify node management. These daemon sets orchestrate operating system updates and configuration changes to the hosts by using standard Kubernetes-style constructs. They include: The machine-config-controller , which coordinates machine upgrades from the control plane. It monitors all of the cluster nodes and orchestrates their configuration updates. The machine-config-daemon daemon set, which runs on each node in the cluster and updates a machine to configuration as defined by machine config and as instructed by the MachineConfigController. When the node detects a change, it drains off its pods, applies the update, and reboots. These changes come in the form of Ignition configuration files that apply the specified machine configuration and control kubelet configuration. The update itself is delivered in a container. This process is key to the success of managing OpenShift Container Platform and RHCOS updates together. The machine-config-server daemon set, which provides the Ignition config files to control plane nodes as they join the cluster. The machine configuration is a subset of the Ignition configuration. The machine-config-daemon reads the machine configuration to see if it needs to do an OSTree update or if it must apply a series of systemd kubelet file changes, configuration changes, or other changes to the operating system or OpenShift Container Platform configuration. When you perform node management operations, you create or modify a KubeletConfig custom resource (CR). Important When changes are made to a machine configuration, the Machine Config Operator (MCO) automatically reboots all corresponding nodes in order for the changes to take effect. To prevent the nodes from automatically rebooting after machine configuration changes, before making the changes, you must pause the autoreboot process by setting the spec.paused field to true in the corresponding machine config pool. When paused, machine configuration changes are not applied until you set the spec.paused field to false and the nodes have rebooted into the new configuration. The following modifications do not trigger a node reboot: When the MCO detects any of the following changes, it applies the update without draining or rebooting the node: Changes to the SSH key in the spec.config.passwd.users.sshAuthorizedKeys parameter of a machine config. Changes to the global pull secret or pull secret in the openshift-config namespace. Automatic rotation of the /etc/kubernetes/kubelet-ca.crt certificate authority (CA) by the Kubernetes API Server Operator. When the MCO detects changes to the /etc/containers/registries.conf file, such as adding or editing an ImageDigestMirrorSet , ImageTagMirrorSet , or ImageContentSourcePolicy object, it drains the corresponding nodes, applies the changes, and uncordons the nodes. The node drain does not happen for the following changes: The addition of a registry with the pull-from-mirror = "digest-only" parameter set for each mirror. The addition of a mirror with the pull-from-mirror = "digest-only" parameter set in a registry. The addition of items to the unqualified-search-registries list. There might be situations where the configuration on a node does not fully match what the currently-applied machine config specifies. This state is called configuration drift . The Machine Config Daemon (MCD) regularly checks the nodes for configuration drift. If the MCD detects configuration drift, the MCO marks the node degraded until an administrator corrects the node configuration. A degraded node is online and operational, but, it cannot be updated. 5.1.1. Machine Config overview The Machine Config Operator (MCO) manages updates to systemd, CRI-O and Kubelet, the kernel, Network Manager and other system features. It also offers a MachineConfig CRD that can write configuration files onto the host (see machine-config-operator ). Understanding what the MCO does and how it interacts with other components is critical to making advanced, system-level changes to an OpenShift Container Platform cluster. Here are some things you should know about the MCO, machine configs, and how they are used: Machine configs are processed alphabetically, in lexicographically increasing order, of their name. The render controller uses the first machine config in the list as the base and appends the rest to the base machine config. A machine config can make a specific change to a file or service on the operating system of each system representing a pool of OpenShift Container Platform nodes. MCO applies changes to operating systems in pools of machines. All OpenShift Container Platform clusters start with worker and control plane node pools. By adding more role labels, you can configure custom pools of nodes. For example, you can set up a custom pool of worker nodes that includes particular hardware features needed by an application. However, examples in this section focus on changes to the default pool types. Important A node can have multiple labels applied that indicate its type, such as master or worker , however it can be a member of only a single machine config pool. After a machine config change, the MCO updates the affected nodes alphabetically by zone, based on the topology.kubernetes.io/zone label. If a zone has more than one node, the oldest nodes are updated first. For nodes that do not use zones, such as in bare metal deployments, the nodes are upgraded by age, with the oldest nodes updated first. The MCO updates the number of nodes as specified by the maxUnavailable field on the machine configuration pool at a time. Some machine configuration must be in place before OpenShift Container Platform is installed to disk. In most cases, this can be accomplished by creating a machine config that is injected directly into the OpenShift Container Platform installer process, instead of running as a postinstallation machine config. In other cases, you might need to do bare metal installation where you pass kernel arguments at OpenShift Container Platform installer startup, to do such things as setting per-node individual IP addresses or advanced disk partitioning. MCO manages items that are set in machine configs. Manual changes you do to your systems will not be overwritten by MCO, unless MCO is explicitly told to manage a conflicting file. In other words, MCO only makes specific updates you request, it does not claim control over the whole node. Manual changes to nodes are strongly discouraged. If you need to decommission a node and start a new one, those direct changes would be lost. MCO is only supported for writing to files in /etc and /var directories, although there are symbolic links to some directories that can be writeable by being symbolically linked to one of those areas. The /opt and /usr/local directories are examples. Ignition is the configuration format used in MachineConfigs. See the Ignition Configuration Specification v3.2.0 for details. Although Ignition config settings can be delivered directly at OpenShift Container Platform installation time, and are formatted in the same way that MCO delivers Ignition configs, MCO has no way of seeing what those original Ignition configs are. Therefore, you should wrap Ignition config settings into a machine config before deploying them. When a file managed by MCO changes outside of MCO, the Machine Config Daemon (MCD) sets the node as degraded . It will not overwrite the offending file, however, and should continue to operate in a degraded state. A key reason for using a machine config is that it will be applied when you spin up new nodes for a pool in your OpenShift Container Platform cluster. The machine-api-operator provisions a new machine and MCO configures it. MCO uses Ignition as the configuration format. OpenShift Container Platform 4.6 moved from Ignition config specification version 2 to version 3. 5.1.1.1. What can you change with machine configs? The kinds of components that MCO can change include: config : Create Ignition config objects (see the Ignition configuration specification ) to do things like modify files, systemd services, and other features on OpenShift Container Platform machines, including: Configuration files : Create or overwrite files in the /var or /etc directory. systemd units : Create and set the status of a systemd service or add to an existing systemd service by dropping in additional settings. users and groups : Change SSH keys in the passwd section postinstallation. Important Changing SSH keys by using a machine config is supported only for the core user. Adding new users by using a machine config is not supported. kernelArguments : Add arguments to the kernel command line when OpenShift Container Platform nodes boot. kernelType : Optionally identify a non-standard kernel to use instead of the standard kernel. Use realtime to use the RT kernel (for RAN). This is only supported on select platforms. extensions : Extend RHCOS features by adding selected pre-packaged software. For this feature, available extensions include usbguard and kernel modules. Custom resources (for ContainerRuntime and Kubelet ) : Outside of machine configs, MCO manages two special custom resources for modifying CRI-O container runtime settings ( ContainerRuntime CR) and the Kubelet service ( Kubelet CR). The MCO is not the only Operator that can change operating system components on OpenShift Container Platform nodes. Other Operators can modify operating system-level features as well. One example is the Node Tuning Operator, which allows you to do node-level tuning through Tuned daemon profiles. Tasks for the MCO configuration that can be done postinstallation are included in the following procedures. See descriptions of RHCOS bare metal installation for system configuration tasks that must be done during or before OpenShift Container Platform installation. There might be situations where the configuration on a node does not fully match what the currently-applied machine config specifies. This state is called configuration drift . The Machine Config Daemon (MCD) regularly checks the nodes for configuration drift. If the MCD detects configuration drift, the MCO marks the node degraded until an administrator corrects the node configuration. A degraded node is online and operational, but, it cannot be updated. For more information on configuration drift, see Understanding configuration drift detection . 5.1.1.2. Project See the openshift-machine-config-operator GitHub site for details. 5.1.2. Understanding the Machine Config Operator node drain behavior When you use a machine config to change a system feature, such as adding new config files, modifying systemd units or kernel arguments, or updating SSH keys, the Machine Config Operator (MCO) applies those changes and ensures that each node is in the desired configuration state. After you make the changes, the MCO generates a new rendered machine config. In the majority of cases, when applying the new rendered machine config, the Operator performs the following steps on each affected node until all of the affected nodes have the updated configuration: Cordon. The MCO marks the node as not schedulable for additional workloads. Drain. The MCO terminates all running workloads on the node, causing the workloads to be rescheduled onto other nodes. Apply. The MCO writes the new configuration to the nodes as needed. Reboot. The MCO restarts the node. Uncordon. The MCO marks the node as schedulable for workloads. Throughout this process, the MCO maintains the required number of pods based on the MaxUnavailable value set in the machine config pool. If the MCO drains pods on the master node, note the following conditions: In single-node OpenShift clusters, the MCO skips the drain operation. The MCO does not drain static pods in order to prevent interference with services, such as etcd. Note In certain cases the nodes are not drained. For more information, see "About the Machine Config Operator." You can mitigate the disruption caused by drain and reboot cycles by disabling control plane reboots. For more information, see "Disabling the Machine Config Operator from automatically rebooting." Additional resources About the Machine Config Operator Disabling the Machine Config Operator from automatically rebooting 5.1.3. Understanding configuration drift detection There might be situations when the on-disk state of a node differs from what is configured in the machine config. This is known as configuration drift . For example, a cluster admin might manually modify a file, a systemd unit file, or a file permission that was configured through a machine config. This causes configuration drift. Configuration drift can cause problems between nodes in a Machine Config Pool or when the machine configs are updated. The Machine Config Operator (MCO) uses the Machine Config Daemon (MCD) to check nodes for configuration drift on a regular basis. If detected, the MCO sets the node and the machine config pool (MCP) to Degraded and reports the error. A degraded node is online and operational, but, it cannot be updated. The MCD performs configuration drift detection upon each of the following conditions: When a node boots. After any of the files (Ignition files and systemd drop-in units) specified in the machine config are modified outside of the machine config. Before a new machine config is applied. Note If you apply a new machine config to the nodes, the MCD temporarily shuts down configuration drift detection. This shutdown is needed because the new machine config necessarily differs from the machine config on the nodes. After the new machine config is applied, the MCD restarts detecting configuration drift using the new machine config. When performing configuration drift detection, the MCD validates that the file contents and permissions fully match what the currently-applied machine config specifies. Typically, the MCD detects configuration drift in less than a second after the detection is triggered. If the MCD detects configuration drift, the MCD performs the following tasks: Emits an error to the console logs Emits a Kubernetes event Stops further detection on the node Sets the node and MCP to degraded You can check if you have a degraded node by listing the MCPs: USD oc get mcp worker If you have a degraded MCP, the DEGRADEDMACHINECOUNT field is non-zero, similar to the following output: Example output NAME CONFIG UPDATED UPDATING DEGRADED MACHINECOUNT READYMACHINECOUNT UPDATEDMACHINECOUNT DEGRADEDMACHINECOUNT AGE worker rendered-worker-404caf3180818d8ac1f50c32f14b57c3 False True True 2 1 1 1 5h51m You can determine if the problem is caused by configuration drift by examining the machine config pool: USD oc describe mcp worker Example output ... Last Transition Time: 2021-12-20T18:54:00Z Message: Node ci-ln-j4h8nkb-72292-pxqxz-worker-a-fjks4 is reporting: "content mismatch for file \"/etc/mco-test-file\"" 1 Reason: 1 nodes are reporting degraded status on sync Status: True Type: NodeDegraded 2 ... 1 This message shows that a node's /etc/mco-test-file file, which was added by the machine config, has changed outside of the machine config. 2 The state of the node is NodeDegraded . Or, if you know which node is degraded, examine that node: USD oc describe node/ci-ln-j4h8nkb-72292-pxqxz-worker-a-fjks4 Example output ... Annotations: cloud.network.openshift.io/egress-ipconfig: [{"interface":"nic0","ifaddr":{"ipv4":"10.0.128.0/17"},"capacity":{"ip":10}}] csi.volume.kubernetes.io/nodeid: {"pd.csi.storage.gke.io":"projects/openshift-gce-devel-ci/zones/us-central1-a/instances/ci-ln-j4h8nkb-72292-pxqxz-worker-a-fjks4"} machine.openshift.io/machine: openshift-machine-api/ci-ln-j4h8nkb-72292-pxqxz-worker-a-fjks4 machineconfiguration.openshift.io/controlPlaneTopology: HighlyAvailable machineconfiguration.openshift.io/currentConfig: rendered-worker-67bd55d0b02b0f659aef33680693a9f9 machineconfiguration.openshift.io/desiredConfig: rendered-worker-67bd55d0b02b0f659aef33680693a9f9 machineconfiguration.openshift.io/reason: content mismatch for file "/etc/mco-test-file" 1 machineconfiguration.openshift.io/state: Degraded 2 ... 1 The error message indicating that configuration drift was detected between the node and the listed machine config. Here the error message indicates that the contents of the /etc/mco-test-file , which was added by the machine config, has changed outside of the machine config. 2 The state of the node is Degraded . You can correct configuration drift and return the node to the Ready state by performing one of the following remediations: Ensure that the contents and file permissions of the files on the node match what is configured in the machine config. You can manually rewrite the file contents or change the file permissions. Generate a force file on the degraded node. The force file causes the MCD to bypass the usual configuration drift detection and reapplies the current machine config. Note Generating a force file on a node causes that node to reboot. Additional resources Disabling Machine Config Operator from automatically rebooting . 5.1.4. Checking machine config pool status To see the status of the Machine Config Operator (MCO), its sub-components, and the resources it manages, use the following oc commands: Procedure To see the number of MCO-managed nodes available on your cluster for each machine config pool (MCP), run the following command: USD oc get machineconfigpool Example output NAME CONFIG UPDATED UPDATING DEGRADED MACHINECOUNT READYMACHINECOUNT UPDATEDMACHINECOUNT DEGRADEDMACHINECOUNT AGE master rendered-master-06c9c4... True False False 3 3 3 0 4h42m worker rendered-worker-f4b64... False True False 3 2 2 0 4h42m where: UPDATED The True status indicates that the MCO has applied the current machine config to the nodes in that MCP. The current machine config is specified in the STATUS field in the oc get mcp output. The False status indicates a node in the MCP is updating. UPDATING The True status indicates that the MCO is applying the desired machine config, as specified in the MachineConfigPool custom resource, to at least one of the nodes in that MCP. The desired machine config is the new, edited machine config. Nodes that are updating might not be available for scheduling. The False status indicates that all nodes in the MCP are updated. DEGRADED A True status indicates the MCO is blocked from applying the current or desired machine config to at least one of the nodes in that MCP, or the configuration is failing. Nodes that are degraded might not be available for scheduling. A False status indicates that all nodes in the MCP are ready. MACHINECOUNT Indicates the total number of machines in that MCP. READYMACHINECOUNT Indicates the total number of machines in that MCP that are ready for scheduling. UPDATEDMACHINECOUNT Indicates the total number of machines in that MCP that have the current machine config. DEGRADEDMACHINECOUNT Indicates the total number of machines in that MCP that are marked as degraded or unreconcilable. In the output, there are three control plane (master) nodes and three worker nodes. The control plane MCP and the associated nodes are updated to the current machine config. The nodes in the worker MCP are being updated to the desired machine config. Two of the nodes in the worker MCP are updated and one is still updating, as indicated by the UPDATEDMACHINECOUNT being 2 . There are no issues, as indicated by the DEGRADEDMACHINECOUNT being 0 and DEGRADED being False . While the nodes in the MCP are updating, the machine config listed under CONFIG is the current machine config, which the MCP is being updated from. When the update is complete, the listed machine config is the desired machine config, which the MCP was updated to. Note If a node is being cordoned, that node is not included in the READYMACHINECOUNT , but is included in the MACHINECOUNT . Also, the MCP status is set to UPDATING . Because the node has the current machine config, it is counted in the UPDATEDMACHINECOUNT total: Example output NAME CONFIG UPDATED UPDATING DEGRADED MACHINECOUNT READYMACHINECOUNT UPDATEDMACHINECOUNT DEGRADEDMACHINECOUNT AGE master rendered-master-06c9c4... True False False 3 3 3 0 4h42m worker rendered-worker-c1b41a... False True False 3 2 3 0 4h42m To check the status of the nodes in an MCP by examining the MachineConfigPool custom resource, run the following command: : USD oc describe mcp worker Example output ... Degraded Machine Count: 0 Machine Count: 3 Observed Generation: 2 Ready Machine Count: 3 Unavailable Machine Count: 0 Updated Machine Count: 3 Events: <none> Note If a node is being cordoned, the node is not included in the Ready Machine Count . It is included in the Unavailable Machine Count : Example output ... Degraded Machine Count: 0 Machine Count: 3 Observed Generation: 2 Ready Machine Count: 2 Unavailable Machine Count: 1 Updated Machine Count: 3 To see each existing MachineConfig object, run the following command: USD oc get machineconfigs Example output NAME GENERATEDBYCONTROLLER IGNITIONVERSION AGE 00-master 2c9371fbb673b97a6fe8b1c52... 3.2.0 5h18m 00-worker 2c9371fbb673b97a6fe8b1c52... 3.2.0 5h18m 01-master-container-runtime 2c9371fbb673b97a6fe8b1c52... 3.2.0 5h18m 01-master-kubelet 2c9371fbb673b97a6fe8b1c52... 3.2.0 5h18m ... rendered-master-dde... 2c9371fbb673b97a6fe8b1c52... 3.2.0 5h18m rendered-worker-fde... 2c9371fbb673b97a6fe8b1c52... 3.2.0 5h18m Note that the MachineConfig objects listed as rendered are not meant to be changed or deleted. To view the contents of a particular machine config (in this case, 01-master-kubelet ), run the following command: USD oc describe machineconfigs 01-master-kubelet The output from the command shows that this MachineConfig object contains both configuration files ( cloud.conf and kubelet.conf ) and a systemd service (Kubernetes Kubelet): Example output Name: 01-master-kubelet ... Spec: Config: Ignition: Version: 3.2.0 Storage: Files: Contents: Source: data:, Mode: 420 Overwrite: true Path: /etc/kubernetes/cloud.conf Contents: Source: data:,kind%3A%20KubeletConfiguration%0AapiVersion%3A%20kubelet.config.k8s.io%2Fv1beta1%0Aauthentication%3A%0A%20%20x509%3A%0A%20%20%20%20clientCAFile%3A%20%2Fetc%2Fkubernetes%2Fkubelet-ca.crt%0A%20%20anonymous... Mode: 420 Overwrite: true Path: /etc/kubernetes/kubelet.conf Systemd: Units: Contents: [Unit] Description=Kubernetes Kubelet Wants=rpc-statd.service network-online.target crio.service After=network-online.target crio.service ExecStart=/usr/bin/hyperkube \ kubelet \ --config=/etc/kubernetes/kubelet.conf \ ... If something goes wrong with a machine config that you apply, you can always back out that change. For example, if you had run oc create -f ./myconfig.yaml to apply a machine config, you could remove that machine config by running the following command: USD oc delete -f ./myconfig.yaml If that was the only problem, the nodes in the affected pool should return to a non-degraded state. This actually causes the rendered configuration to roll back to its previously rendered state. If you add your own machine configs to your cluster, you can use the commands shown in the example to check their status and the related status of the pool to which they are applied. 5.2. Using MachineConfig objects to configure nodes You can use the tasks in this section to create MachineConfig objects that modify files, systemd unit files, and other operating system features running on OpenShift Container Platform nodes. For more ideas on working with machine configs, see content related to updating SSH authorized keys, verifying image signatures , enabling SCTP , and configuring iSCSI initiatornames for OpenShift Container Platform. OpenShift Container Platform supports Ignition specification version 3.2 . All new machine configs you create going forward should be based on Ignition specification version 3.2. If you are upgrading your OpenShift Container Platform cluster, any existing Ignition specification version 2.x machine configs will be translated automatically to specification version 3.2. There might be situations where the configuration on a node does not fully match what the currently-applied machine config specifies. This state is called configuration drift . The Machine Config Daemon (MCD) regularly checks the nodes for configuration drift. If the MCD detects configuration drift, the MCO marks the node degraded until an administrator corrects the node configuration. A degraded node is online and operational, but, it cannot be updated. For more information on configuration drift, see Understanding configuration drift detection . Tip Use the following "Configuring chrony time service" procedure as a model for how to go about adding other configuration files to OpenShift Container Platform nodes. 5.2.1. Configuring chrony time service You can set the time server and related settings used by the chrony time service ( chronyd ) by modifying the contents of the chrony.conf file and passing those contents to your nodes as a machine config. Procedure Create a Butane config including the contents of the chrony.conf file. For example, to configure chrony on worker nodes, create a 99-worker-chrony.bu file. Note See "Creating machine configs with Butane" for information about Butane. variant: openshift version: 4.13.0 metadata: name: 99-worker-chrony 1 labels: machineconfiguration.openshift.io/role: worker 2 storage: files: - path: /etc/chrony.conf mode: 0644 3 overwrite: true contents: inline: | pool 0.rhel.pool.ntp.org iburst 4 driftfile /var/lib/chrony/drift makestep 1.0 3 rtcsync logdir /var/log/chrony 1 2 On control plane nodes, substitute master for worker in both of these locations. 3 Specify an octal value mode for the mode field in the machine config file. After creating the file and applying the changes, the mode is converted to a decimal value. You can check the YAML file with the command oc get mc <mc-name> -o yaml . 4 Specify any valid, reachable time source, such as the one provided by your DHCP server. Alternately, you can specify any of the following NTP servers: 1.rhel.pool.ntp.org , 2.rhel.pool.ntp.org , or 3.rhel.pool.ntp.org . Use Butane to generate a MachineConfig object file, 99-worker-chrony.yaml , containing the configuration to be delivered to the nodes: USD butane 99-worker-chrony.bu -o 99-worker-chrony.yaml Apply the configurations in one of two ways: If the cluster is not running yet, after you generate manifest files, add the MachineConfig object file to the <installation_directory>/openshift directory, and then continue to create the cluster. If the cluster is already running, apply the file: USD oc apply -f ./99-worker-chrony.yaml Additional resources Creating machine configs with Butane 5.2.2. Disabling the chrony time service You can disable the chrony time service ( chronyd ) for nodes with a specific role by using a MachineConfig custom resource (CR). Prerequisites Install the OpenShift CLI ( oc ). Log in as a user with cluster-admin privileges. Procedure Create the MachineConfig CR that disables chronyd for the specified node role. Save the following YAML in the disable-chronyd.yaml file: apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfig metadata: labels: machineconfiguration.openshift.io/role: <node_role> 1 name: disable-chronyd spec: config: ignition: version: 3.2.0 systemd: units: - contents: | [Unit] Description=NTP client/server Documentation=man:chronyd(8) man:chrony.conf(5) After=ntpdate.service sntp.service ntpd.service Conflicts=ntpd.service systemd-timesyncd.service ConditionCapability=CAP_SYS_TIME [Service] Type=forking PIDFile=/run/chrony/chronyd.pid EnvironmentFile=-/etc/sysconfig/chronyd ExecStart=/usr/sbin/chronyd USDOPTIONS ExecStartPost=/usr/libexec/chrony-helper update-daemon PrivateTmp=yes ProtectHome=yes ProtectSystem=full [Install] WantedBy=multi-user.target enabled: false name: "chronyd.service" 1 Node role where you want to disable chronyd , for example, master . Create the MachineConfig CR by running the following command: USD oc create -f disable-chronyd.yaml 5.2.3. Adding kernel arguments to nodes In some special cases, you might want to add kernel arguments to a set of nodes in your cluster. This should only be done with caution and clear understanding of the implications of the arguments you set. Warning Improper use of kernel arguments can result in your systems becoming unbootable. Examples of kernel arguments you could set include: nosmt : Disables symmetric multithreading (SMT) in the kernel. Multithreading allows multiple logical threads for each CPU. You could consider nosmt in multi-tenant environments to reduce risks from potential cross-thread attacks. By disabling SMT, you essentially choose security over performance. systemd.unified_cgroup_hierarchy : Enables Linux control group version 2 (cgroup v2). cgroup v2 is the version of the kernel control group and offers multiple improvements. enforcing=0 : Configures Security Enhanced Linux (SELinux) to run in permissive mode. In permissive mode, the system acts as if SELinux is enforcing the loaded security policy, including labeling objects and emitting access denial entries in the logs, but it does not actually deny any operations. While not supported for production systems, permissive mode can be helpful for debugging. Warning Disabling SELinux on RHCOS in production is not supported. Once SELinux has been disabled on a node, it must be re-provisioned before re-inclusion in a production cluster. See Kernel.org kernel parameters for a list and descriptions of kernel arguments. In the following procedure, you create a MachineConfig object that identifies: A set of machines to which you want to add the kernel argument. In this case, machines with a worker role. Kernel arguments that are appended to the end of the existing kernel arguments. A label that indicates where in the list of machine configs the change is applied. Prerequisites Have administrative privilege to a working OpenShift Container Platform cluster. Procedure List existing MachineConfig objects for your OpenShift Container Platform cluster to determine how to label your machine config: USD oc get MachineConfig Example output NAME GENERATEDBYCONTROLLER IGNITIONVERSION AGE 00-master 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 00-worker 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-master-container-runtime 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-master-kubelet 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-worker-container-runtime 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-worker-kubelet 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 99-master-generated-registries 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 99-master-ssh 3.2.0 40m 99-worker-generated-registries 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 99-worker-ssh 3.2.0 40m rendered-master-23e785de7587df95a4b517e0647e5ab7 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m rendered-worker-5d596d9293ca3ea80c896a1191735bb1 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m Create a MachineConfig object file that identifies the kernel argument (for example, 05-worker-kernelarg-selinuxpermissive.yaml ) apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfig metadata: labels: machineconfiguration.openshift.io/role: worker 1 name: 05-worker-kernelarg-selinuxpermissive 2 spec: kernelArguments: - enforcing=0 3 1 Applies the new kernel argument only to worker nodes. 2 Named to identify where it fits among the machine configs (05) and what it does (adds a kernel argument to configure SELinux permissive mode). 3 Identifies the exact kernel argument as enforcing=0 . Create the new machine config: USD oc create -f 05-worker-kernelarg-selinuxpermissive.yaml Check the machine configs to see that the new one was added: USD oc get MachineConfig Example output NAME GENERATEDBYCONTROLLER IGNITIONVERSION AGE 00-master 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 00-worker 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-master-container-runtime 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-master-kubelet 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-worker-container-runtime 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-worker-kubelet 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 05-worker-kernelarg-selinuxpermissive 3.2.0 105s 99-master-generated-registries 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 99-master-ssh 3.2.0 40m 99-worker-generated-registries 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 99-worker-ssh 3.2.0 40m rendered-master-23e785de7587df95a4b517e0647e5ab7 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m rendered-worker-5d596d9293ca3ea80c896a1191735bb1 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m Check the nodes: USD oc get nodes Example output NAME STATUS ROLES AGE VERSION ip-10-0-136-161.ec2.internal Ready worker 28m v1.26.0 ip-10-0-136-243.ec2.internal Ready master 34m v1.26.0 ip-10-0-141-105.ec2.internal Ready,SchedulingDisabled worker 28m v1.26.0 ip-10-0-142-249.ec2.internal Ready master 34m v1.26.0 ip-10-0-153-11.ec2.internal Ready worker 28m v1.26.0 ip-10-0-153-150.ec2.internal Ready master 34m v1.26.0 You can see that scheduling on each worker node is disabled as the change is being applied. Check that the kernel argument worked by going to one of the worker nodes and listing the kernel command line arguments (in /proc/cmdline on the host): USD oc debug node/ip-10-0-141-105.ec2.internal Example output Starting pod/ip-10-0-141-105ec2internal-debug ... To use host binaries, run `chroot /host` sh-4.2# cat /host/proc/cmdline BOOT_IMAGE=/ostree/rhcos-... console=tty0 console=ttyS0,115200n8 rootflags=defaults,prjquota rw root=UUID=fd0... ostree=/ostree/boot.0/rhcos/16... coreos.oem.id=qemu coreos.oem.id=ec2 ignition.platform.id=ec2 enforcing=0 sh-4.2# exit You should see the enforcing=0 argument added to the other kernel arguments. 5.2.4. Enabling multipathing with kernel arguments on RHCOS Red Hat Enterprise Linux CoreOS (RHCOS) supports multipathing on the primary disk, allowing stronger resilience to hardware failure to achieve higher host availability. Postinstallation support is available by activating multipathing via the machine config. Important Enabling multipathing during installation is supported and recommended for nodes provisioned in OpenShift Container Platform. In setups where any I/O to non-optimized paths results in I/O system errors, you must enable multipathing at installation time. For more information about enabling multipathing during installation time, see "Enabling multipathing post installation" in the Installing on bare metal documentation. Important On IBM Z and IBM(R) LinuxONE, you can enable multipathing only if you configured your cluster for it during installation. For more information, see "Installing RHCOS and starting the OpenShift Container Platform bootstrap process" in Installing a cluster with z/VM on IBM Z and IBM(R) LinuxONE . Important When an OpenShift Container Platform cluster is installed or configured as a postinstallation activity on a single VIOS host with "vSCSI" storage on IBM Power(R) with multipath configured, the CoreOS nodes with multipath enabled fail to boot. This behavior is expected, as only one path is available to the node. Prerequisites You have a running OpenShift Container Platform cluster. You are logged in to the cluster as a user with administrative privileges. You have confirmed that the disk is enabled for multipathing. Multipathing is only supported on hosts that are connected to a SAN via an HBA adapter. Procedure To enable multipathing postinstallation on control plane nodes: Create a machine config file, such as 99-master-kargs-mpath.yaml , that instructs the cluster to add the master label and that identifies the multipath kernel argument, for example: apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfig metadata: labels: machineconfiguration.openshift.io/role: "master" name: 99-master-kargs-mpath spec: kernelArguments: - 'rd.multipath=default' - 'root=/dev/disk/by-label/dm-mpath-root' To enable multipathing postinstallation on worker nodes: Create a machine config file, such as 99-worker-kargs-mpath.yaml , that instructs the cluster to add the worker label and that identifies the multipath kernel argument, for example: apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfig metadata: labels: machineconfiguration.openshift.io/role: "worker" name: 99-worker-kargs-mpath spec: kernelArguments: - 'rd.multipath=default' - 'root=/dev/disk/by-label/dm-mpath-root' Create the new machine config by using either the master or worker YAML file you previously created: USD oc create -f ./99-worker-kargs-mpath.yaml Check the machine configs to see that the new one was added: USD oc get MachineConfig Example output NAME GENERATEDBYCONTROLLER IGNITIONVERSION AGE 00-master 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 00-worker 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-master-container-runtime 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-master-kubelet 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-worker-container-runtime 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-worker-kubelet 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 99-master-generated-registries 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 99-master-ssh 3.2.0 40m 99-worker-generated-registries 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 99-worker-kargs-mpath 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 105s 99-worker-ssh 3.2.0 40m rendered-master-23e785de7587df95a4b517e0647e5ab7 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m rendered-worker-5d596d9293ca3ea80c896a1191735bb1 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m Check the nodes: USD oc get nodes Example output NAME STATUS ROLES AGE VERSION ip-10-0-136-161.ec2.internal Ready worker 28m v1.26.0 ip-10-0-136-243.ec2.internal Ready master 34m v1.26.0 ip-10-0-141-105.ec2.internal Ready,SchedulingDisabled worker 28m v1.26.0 ip-10-0-142-249.ec2.internal Ready master 34m v1.26.0 ip-10-0-153-11.ec2.internal Ready worker 28m v1.26.0 ip-10-0-153-150.ec2.internal Ready master 34m v1.26.0 You can see that scheduling on each worker node is disabled as the change is being applied. Check that the kernel argument worked by going to one of the worker nodes and listing the kernel command line arguments (in /proc/cmdline on the host): USD oc debug node/ip-10-0-141-105.ec2.internal Example output Starting pod/ip-10-0-141-105ec2internal-debug ... To use host binaries, run `chroot /host` sh-4.2# cat /host/proc/cmdline ... rd.multipath=default root=/dev/disk/by-label/dm-mpath-root ... sh-4.2# exit You should see the added kernel arguments. Additional resources See Enabling multipathing with kernel arguments on RHCOS for more information about enabling multipathing during installation time. 5.2.5. Adding a real-time kernel to nodes Some OpenShift Container Platform workloads require a high degree of determinism.While Linux is not a real-time operating system, the Linux real-time kernel includes a preemptive scheduler that provides the operating system with real-time characteristics. If your OpenShift Container Platform workloads require these real-time characteristics, you can switch your machines to the Linux real-time kernel. For OpenShift Container Platform, 4.13 you can make this switch using a MachineConfig object. Although making the change is as simple as changing a machine config kernelType setting to realtime , there are a few other considerations before making the change: Currently, real-time kernel is supported only on worker nodes, and only for radio access network (RAN) use. The following procedure is fully supported with bare metal installations that use systems that are certified for Red Hat Enterprise Linux for Real Time 8. Real-time support in OpenShift Container Platform is limited to specific subscriptions. The following procedure is also supported for use with Google Cloud Platform. Prerequisites Have a running OpenShift Container Platform cluster (version 4.4 or later). Log in to the cluster as a user with administrative privileges. Procedure Create a machine config for the real-time kernel: Create a YAML file (for example, 99-worker-realtime.yaml ) that contains a MachineConfig object for the realtime kernel type. This example tells the cluster to use a real-time kernel for all worker nodes: USD cat << EOF > 99-worker-realtime.yaml apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfig metadata: labels: machineconfiguration.openshift.io/role: "worker" name: 99-worker-realtime spec: kernelType: realtime EOF Add the machine config to the cluster. Type the following to add the machine config to the cluster: USD oc create -f 99-worker-realtime.yaml Check the real-time kernel: Once each impacted node reboots, log in to the cluster and run the following commands to make sure that the real-time kernel has replaced the regular kernel for the set of nodes you configured: USD oc get nodes Example output NAME STATUS ROLES AGE VERSION ip-10-0-143-147.us-east-2.compute.internal Ready worker 103m v1.26.0 ip-10-0-146-92.us-east-2.compute.internal Ready worker 101m v1.26.0 ip-10-0-169-2.us-east-2.compute.internal Ready worker 102m v1.26.0 USD oc debug node/ip-10-0-143-147.us-east-2.compute.internal Example output Starting pod/ip-10-0-143-147us-east-2computeinternal-debug ... To use host binaries, run `chroot /host` sh-4.4# uname -a Linux <worker_node> 4.18.0-147.3.1.rt24.96.el8_1.x86_64 #1 SMP PREEMPT RT Wed Nov 27 18:29:55 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux The kernel name contains rt and text "PREEMPT RT" indicates that this is a real-time kernel. To go back to the regular kernel, delete the MachineConfig object: USD oc delete -f 99-worker-realtime.yaml 5.2.6. Configuring journald settings If you need to configure settings for the journald service on OpenShift Container Platform nodes, you can do that by modifying the appropriate configuration file and passing the file to the appropriate pool of nodes as a machine config. This procedure describes how to modify journald rate limiting settings in the /etc/systemd/journald.conf file and apply them to worker nodes. See the journald.conf man page for information on how to use that file. Prerequisites Have a running OpenShift Container Platform cluster. Log in to the cluster as a user with administrative privileges. Procedure Create a Butane config file, 40-worker-custom-journald.bu , that includes an /etc/systemd/journald.conf file with the required settings. Note See "Creating machine configs with Butane" for information about Butane. variant: openshift version: 4.13.0 metadata: name: 40-worker-custom-journald labels: machineconfiguration.openshift.io/role: worker storage: files: - path: /etc/systemd/journald.conf mode: 0644 overwrite: true contents: inline: | # Disable rate limiting RateLimitInterval=1s RateLimitBurst=10000 Storage=volatile Compress=no MaxRetentionSec=30s Use Butane to generate a MachineConfig object file, 40-worker-custom-journald.yaml , containing the configuration to be delivered to the worker nodes: USD butane 40-worker-custom-journald.bu -o 40-worker-custom-journald.yaml Apply the machine config to the pool: USD oc apply -f 40-worker-custom-journald.yaml Check that the new machine config is applied and that the nodes are not in a degraded state. It might take a few minutes. The worker pool will show the updates in progress, as each node successfully has the new machine config applied: USD oc get machineconfigpool NAME CONFIG UPDATED UPDATING DEGRADED MACHINECOUNT READYMACHINECOUNT UPDATEDMACHINECOUNT DEGRADEDMACHINECOUNT AGE master rendered-master-35 True False False 3 3 3 0 34m worker rendered-worker-d8 False True False 3 1 1 0 34m To check that the change was applied, you can log in to a worker node: USD oc get node | grep worker ip-10-0-0-1.us-east-2.compute.internal Ready worker 39m v0.0.0-master+USDFormat:%hUSD USD oc debug node/ip-10-0-0-1.us-east-2.compute.internal Starting pod/ip-10-0-141-142us-east-2computeinternal-debug ... ... sh-4.2# chroot /host sh-4.4# cat /etc/systemd/journald.conf # Disable rate limiting RateLimitInterval=1s RateLimitBurst=10000 Storage=volatile Compress=no MaxRetentionSec=30s sh-4.4# exit Additional resources Creating machine configs with Butane 5.2.7. Adding extensions to RHCOS RHCOS is a minimal container-oriented RHEL operating system, designed to provide a common set of capabilities to OpenShift Container Platform clusters across all platforms. While adding software packages to RHCOS systems is generally discouraged, the MCO provides an extensions feature you can use to add a minimal set of features to RHCOS nodes. Currently, the following extensions are available: usbguard : Adding the usbguard extension protects RHCOS systems from attacks from intrusive USB devices. See USBGuard for details. kerberos : Adding the kerberos extension provides a mechanism that allows both users and machines to identify themselves to the network to receive defined, limited access to the areas and services that an administrator has configured. See Using Kerberos for details, including how to set up a Kerberos client and mount a Kerberized NFS share. The following procedure describes how to use a machine config to add one or more extensions to your RHCOS nodes. Prerequisites Have a running OpenShift Container Platform cluster (version 4.6 or later). Log in to the cluster as a user with administrative privileges. Procedure Create a machine config for extensions: Create a YAML file (for example, 80-extensions.yaml ) that contains a MachineConfig extensions object. This example tells the cluster to add the usbguard extension. USD cat << EOF > 80-extensions.yaml apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfig metadata: labels: machineconfiguration.openshift.io/role: worker name: 80-worker-extensions spec: config: ignition: version: 3.2.0 extensions: - usbguard EOF Add the machine config to the cluster. Type the following to add the machine config to the cluster: USD oc create -f 80-extensions.yaml This sets all worker nodes to have rpm packages for usbguard installed. Check that the extensions were applied: USD oc get machineconfig 80-worker-extensions Example output NAME GENERATEDBYCONTROLLER IGNITIONVERSION AGE 80-worker-extensions 3.2.0 57s Check that the new machine config is now applied and that the nodes are not in a degraded state. It may take a few minutes. The worker pool will show the updates in progress, as each machine successfully has the new machine config applied: USD oc get machineconfigpool Example output NAME CONFIG UPDATED UPDATING DEGRADED MACHINECOUNT READYMACHINECOUNT UPDATEDMACHINECOUNT DEGRADEDMACHINECOUNT AGE master rendered-master-35 True False False 3 3 3 0 34m worker rendered-worker-d8 False True False 3 1 1 0 34m Check the extensions. To check that the extension was applied, run: USD oc get node | grep worker Example output NAME STATUS ROLES AGE VERSION ip-10-0-169-2.us-east-2.compute.internal Ready worker 102m v1.26.0 USD oc debug node/ip-10-0-169-2.us-east-2.compute.internal Example output ... To use host binaries, run `chroot /host` sh-4.4# chroot /host sh-4.4# rpm -q usbguard usbguard-0.7.4-4.el8.x86_64.rpm 5.2.8. Loading custom firmware blobs in the machine config manifest Because the default location for firmware blobs in /usr/lib is read-only, you can locate a custom firmware blob by updating the search path. This enables you to load local firmware blobs in the machine config manifest when the blobs are not managed by RHCOS. Procedure Create a Butane config file, 98-worker-firmware-blob.bu , that updates the search path so that it is root-owned and writable to local storage. The following example places the custom blob file from your local workstation onto nodes under /var/lib/firmware . Note See "Creating machine configs with Butane" for information about Butane. Butane config file for custom firmware blob variant: openshift version: 4.13.0 metadata: labels: machineconfiguration.openshift.io/role: worker name: 98-worker-firmware-blob storage: files: - path: /var/lib/firmware/<package_name> 1 contents: local: <package_name> 2 mode: 0644 3 openshift: kernel_arguments: - 'firmware_class.path=/var/lib/firmware' 4 1 Sets the path on the node where the firmware package is copied to. 2 Specifies a file with contents that are read from a local file directory on the system running Butane. The path of the local file is relative to a files-dir directory, which must be specified by using the --files-dir option with Butane in the following step. 3 Sets the permissions for the file on the RHCOS node. It is recommended to set 0644 permissions. 4 The firmware_class.path parameter customizes the kernel search path of where to look for the custom firmware blob that was copied from your local workstation onto the root file system of the node. This example uses /var/lib/firmware as the customized path. Run Butane to generate a MachineConfig object file that uses a copy of the firmware blob on your local workstation named 98-worker-firmware-blob.yaml . The firmware blob contains the configuration to be delivered to the nodes. The following example uses the --files-dir option to specify the directory on your workstation where the local file or files are located: USD butane 98-worker-firmware-blob.bu -o 98-worker-firmware-blob.yaml --files-dir <directory_including_package_name> Apply the configurations to the nodes in one of two ways: If the cluster is not running yet, after you generate manifest files, add the MachineConfig object file to the <installation_directory>/openshift directory, and then continue to create the cluster. If the cluster is already running, apply the file: USD oc apply -f 98-worker-firmware-blob.yaml A MachineConfig object YAML file is created for you to finish configuring your machines. Save the Butane config in case you need to update the MachineConfig object in the future. Additional resources Creating machine configs with Butane 5.3. Configuring MCO-related custom resources Besides managing MachineConfig objects, the MCO manages two custom resources (CRs): KubeletConfig and ContainerRuntimeConfig . Those CRs let you change node-level settings impacting how the Kubelet and CRI-O container runtime services behave. 5.3.1. Creating a KubeletConfig CRD to edit kubelet parameters The kubelet configuration is currently serialized as an Ignition configuration, so it can be directly edited. However, there is also a new kubelet-config-controller added to the Machine Config Controller (MCC). This lets you use a KubeletConfig custom resource (CR) to edit the kubelet parameters. Note As the fields in the kubeletConfig object are passed directly to the kubelet from upstream Kubernetes, the kubelet validates those values directly. Invalid values in the kubeletConfig object might cause cluster nodes to become unavailable. For valid values, see the Kubernetes documentation . Consider the following guidance: Edit an existing KubeletConfig CR to modify existing settings or add new settings, instead of creating a CR for each change. It is recommended that you create a CR only to modify a different machine config pool, or for changes that are intended to be temporary, so that you can revert the changes. Create one KubeletConfig CR for each machine config pool with all the config changes you want for that pool. As needed, create multiple KubeletConfig CRs with a limit of 10 per cluster. For the first KubeletConfig CR, the Machine Config Operator (MCO) creates a machine config appended with kubelet . With each subsequent CR, the controller creates another kubelet machine config with a numeric suffix. For example, if you have a kubelet machine config with a -2 suffix, the kubelet machine config is appended with -3 . Note If you are applying a kubelet or container runtime config to a custom machine config pool, the custom role in the machineConfigSelector must match the name of the custom machine config pool. For example, because the following custom machine config pool is named infra , the custom role must also be infra : apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfigPool metadata: name: infra spec: machineConfigSelector: matchExpressions: - {key: machineconfiguration.openshift.io/role, operator: In, values: [worker,infra]} # ... If you want to delete the machine configs, delete them in reverse order to avoid exceeding the limit. For example, you delete the kubelet-3 machine config before deleting the kubelet-2 machine config. Note If you have a machine config with a kubelet-9 suffix, and you create another KubeletConfig CR, a new machine config is not created, even if there are fewer than 10 kubelet machine configs. Example KubeletConfig CR USD oc get kubeletconfig NAME AGE set-kubelet-config 15m Example showing a KubeletConfig machine config USD oc get mc | grep kubelet ... 99-worker-generated-kubelet-1 b5c5119de007945b6fe6fb215db3b8e2ceb12511 3.2.0 26m ... The following procedure is an example to show how to configure the maximum number of pods per node, the maximum PIDs per node, and the maximum container log size size on the worker nodes. Prerequisites Obtain the label associated with the static MachineConfigPool CR for the type of node you want to configure. Perform one of the following steps: View the machine config pool: USD oc describe machineconfigpool <name> For example: USD oc describe machineconfigpool worker Example output apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfigPool metadata: creationTimestamp: 2019-02-08T14:52:39Z generation: 1 labels: custom-kubelet: set-kubelet-config 1 1 If a label has been added it appears under labels . If the label is not present, add a key/value pair: USD oc label machineconfigpool worker custom-kubelet=set-kubelet-config Procedure View the available machine configuration objects that you can select: USD oc get machineconfig By default, the two kubelet-related configs are 01-master-kubelet and 01-worker-kubelet . Check the current value for the maximum pods per node: USD oc describe node <node_name> For example: USD oc describe node ci-ln-5grqprb-f76d1-ncnqq-worker-a-mdv94 Look for value: pods: <value> in the Allocatable stanza: Example output Allocatable: attachable-volumes-aws-ebs: 25 cpu: 3500m hugepages-1Gi: 0 hugepages-2Mi: 0 memory: 15341844Ki pods: 250 Configure the worker nodes as needed: Create a YAML file similar to the following that contains the kubelet configuration: Important Kubelet configurations that target a specific machine config pool also affect any dependent pools. For example, creating a kubelet configuration for the pool containing worker nodes will also apply to any subset pools, including the pool containing infrastructure nodes. To avoid this, you must create a new machine config pool with a selection expression that only includes worker nodes, and have your kubelet configuration target this new pool. apiVersion: machineconfiguration.openshift.io/v1 kind: KubeletConfig metadata: name: set-kubelet-config spec: machineConfigPoolSelector: matchLabels: custom-kubelet: set-kubelet-config 1 kubeletConfig: 2 podPidsLimit: 8192 containerLogMaxSize: 50Mi maxPods: 500 1 Enter the label from the machine config pool. 2 Add the kubelet configuration. For example: Use podPidsLimit to set the maximum number of PIDs in any pod. Use containerLogMaxSize to set the maximum size of the container log file before it is rotated. Use maxPods to set the maximum pods per node. Note The rate at which the kubelet talks to the API server depends on queries per second (QPS) and burst values. The default values, 50 for kubeAPIQPS and 100 for kubeAPIBurst , are sufficient if there are limited pods running on each node. It is recommended to update the kubelet QPS and burst rates if there are enough CPU and memory resources on the node. apiVersion: machineconfiguration.openshift.io/v1 kind: KubeletConfig metadata: name: set-kubelet-config spec: machineConfigPoolSelector: matchLabels: custom-kubelet: set-kubelet-config kubeletConfig: maxPods: <pod_count> kubeAPIBurst: <burst_rate> kubeAPIQPS: <QPS> Update the machine config pool for workers with the label: USD oc label machineconfigpool worker custom-kubelet=set-kubelet-config Create the KubeletConfig object: USD oc create -f change-maxPods-cr.yaml Verification Verify that the KubeletConfig object is created: USD oc get kubeletconfig Example output NAME AGE set-kubelet-config 15m Depending on the number of worker nodes in the cluster, wait for the worker nodes to be rebooted one by one. For a cluster with 3 worker nodes, this could take about 10 to 15 minutes. Verify that the changes are applied to the node: Check on a worker node that the maxPods value changed: USD oc describe node <node_name> Locate the Allocatable stanza: ... Allocatable: attachable-volumes-gce-pd: 127 cpu: 3500m ephemeral-storage: 123201474766 hugepages-1Gi: 0 hugepages-2Mi: 0 memory: 14225400Ki pods: 500 1 ... 1 In this example, the pods parameter should report the value you set in the KubeletConfig object. Verify the change in the KubeletConfig object: USD oc get kubeletconfigs set-kubelet-config -o yaml This should show a status of True and type:Success , as shown in the following example: spec: kubeletConfig: containerLogMaxSize: 50Mi maxPods: 500 podPidsLimit: 8192 machineConfigPoolSelector: matchLabels: custom-kubelet: set-kubelet-config status: conditions: - lastTransitionTime: "2021-06-30T17:04:07Z" message: Success status: "True" type: Success 5.3.2. Creating a ContainerRuntimeConfig CR to edit CRI-O parameters You can change some of the settings associated with the OpenShift Container Platform CRI-O runtime for the nodes associated with a specific machine config pool (MCP). Using a ContainerRuntimeConfig custom resource (CR), you set the configuration values and add a label to match the MCP. The MCO then rebuilds the crio.conf and storage.conf configuration files on the associated nodes with the updated values. Note To revert the changes implemented by using a ContainerRuntimeConfig CR, you must delete the CR. Removing the label from the machine config pool does not revert the changes. You can modify the following settings by using a ContainerRuntimeConfig CR: Log level : The logLevel parameter sets the CRI-O log_level parameter, which is the level of verbosity for log messages. The default is info ( log_level = info ). Other options include fatal , panic , error , warn , debug , and trace . Overlay size : The overlaySize parameter sets the CRI-O Overlay storage driver size parameter, which is the maximum size of a container image. Container runtime : The defaultRuntime parameter sets the container runtime to either runc or crun . The default is runc . You should have one ContainerRuntimeConfig CR for each machine config pool with all the config changes you want for that pool. If you are applying the same content to all the pools, you only need one ContainerRuntimeConfig CR for all the pools. You should edit an existing ContainerRuntimeConfig CR to modify existing settings or add new settings instead of creating a new CR for each change. It is recommended to create a new ContainerRuntimeConfig CR only to modify a different machine config pool, or for changes that are intended to be temporary so that you can revert the changes. You can create multiple ContainerRuntimeConfig CRs, as needed, with a limit of 10 per cluster. For the first ContainerRuntimeConfig CR, the MCO creates a machine config appended with containerruntime . With each subsequent CR, the controller creates a new containerruntime machine config with a numeric suffix. For example, if you have a containerruntime machine config with a -2 suffix, the containerruntime machine config is appended with -3 . If you want to delete the machine configs, you should delete them in reverse order to avoid exceeding the limit. For example, you should delete the containerruntime-3 machine config before deleting the containerruntime-2 machine config. Note If you have a machine config with a containerruntime-9 suffix, and you create another ContainerRuntimeConfig CR, a new machine config is not created, even if there are fewer than 10 containerruntime machine configs. Example showing multiple ContainerRuntimeConfig CRs USD oc get ctrcfg Example output NAME AGE ctr-overlay 15m ctr-level 5m45s Example showing multiple containerruntime machine configs USD oc get mc | grep container Example output ... 01-master-container-runtime b5c5119de007945b6fe6fb215db3b8e2ceb12511 3.2.0 57m ... 01-worker-container-runtime b5c5119de007945b6fe6fb215db3b8e2ceb12511 3.2.0 57m ... 99-worker-generated-containerruntime b5c5119de007945b6fe6fb215db3b8e2ceb12511 3.2.0 26m 99-worker-generated-containerruntime-1 b5c5119de007945b6fe6fb215db3b8e2ceb12511 3.2.0 17m 99-worker-generated-containerruntime-2 b5c5119de007945b6fe6fb215db3b8e2ceb12511 3.2.0 7m26s ... The following example sets the log_level field to debug and sets the overlay size to 8 GB: Example ContainerRuntimeConfig CR apiVersion: machineconfiguration.openshift.io/v1 kind: ContainerRuntimeConfig metadata: name: overlay-size spec: machineConfigPoolSelector: matchLabels: pools.operator.machineconfiguration.openshift.io/worker: '' 1 containerRuntimeConfig: logLevel: debug 2 overlaySize: 8G 3 defaultRuntime: "crun" 4 1 Specifies the machine config pool label. For a container runtime config, the role must match the name of the associated machine config pool. 2 Optional: Specifies the level of verbosity for log messages. 3 Optional: Specifies the maximum size of a container image. 4 Optional: Specifies the container runtime to deploy to new containers. The default value is runc . Procedure To change CRI-O settings using the ContainerRuntimeConfig CR: Create a YAML file for the ContainerRuntimeConfig CR: apiVersion: machineconfiguration.openshift.io/v1 kind: ContainerRuntimeConfig metadata: name: overlay-size spec: machineConfigPoolSelector: matchLabels: pools.operator.machineconfiguration.openshift.io/worker: '' 1 containerRuntimeConfig: 2 logLevel: debug overlaySize: 8G 1 Specify a label for the machine config pool that you want you want to modify. 2 Set the parameters as needed. Create the ContainerRuntimeConfig CR: USD oc create -f <file_name>.yaml Verify that the CR is created: USD oc get ContainerRuntimeConfig Example output NAME AGE overlay-size 3m19s Check that a new containerruntime machine config is created: USD oc get machineconfigs | grep containerrun Example output 99-worker-generated-containerruntime 2c9371fbb673b97a6fe8b1c52691999ed3a1bfc2 3.2.0 31s Monitor the machine config pool until all are shown as ready: USD oc get mcp worker Example output NAME CONFIG UPDATED UPDATING DEGRADED MACHINECOUNT READYMACHINECOUNT UPDATEDMACHINECOUNT DEGRADEDMACHINECOUNT AGE worker rendered-worker-169 False True False 3 1 1 0 9h Verify that the settings were applied in CRI-O: Open an oc debug session to a node in the machine config pool and run chroot /host . USD oc debug node/<node_name> sh-4.4# chroot /host Verify the changes in the crio.conf file: sh-4.4# crio config | grep 'log_level' Example output log_level = "debug" Verify the changes in the `storage.conf`file: sh-4.4# head -n 7 /etc/containers/storage.conf Example output 5.3.3. Setting the default maximum container root partition size for Overlay with CRI-O The root partition of each container shows all of the available disk space of the underlying host. Follow this guidance to set a maximum partition size for the root disk of all containers. To configure the maximum Overlay size, as well as other CRI-O options like the log level, you can create the following ContainerRuntimeConfig custom resource definition (CRD): apiVersion: machineconfiguration.openshift.io/v1 kind: ContainerRuntimeConfig metadata: name: overlay-size spec: machineConfigPoolSelector: matchLabels: custom-crio: overlay-size containerRuntimeConfig: logLevel: debug overlaySize: 8G Procedure Create the configuration object: USD oc apply -f overlaysize.yml To apply the new CRI-O configuration to your worker nodes, edit the worker machine config pool: USD oc edit machineconfigpool worker Add the custom-crio label based on the matchLabels name you set in the ContainerRuntimeConfig CRD: apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfigPool metadata: creationTimestamp: "2020-07-09T15:46:34Z" generation: 3 labels: custom-crio: overlay-size machineconfiguration.openshift.io/mco-built-in: "" Save the changes, then view the machine configs: USD oc get machineconfigs New 99-worker-generated-containerruntime and rendered-worker-xyz objects are created: Example output 99-worker-generated-containerruntime 4173030d89fbf4a7a0976d1665491a4d9a6e54f1 3.2.0 7m42s rendered-worker-xyz 4173030d89fbf4a7a0976d1665491a4d9a6e54f1 3.2.0 7m36s After those objects are created, monitor the machine config pool for the changes to be applied: USD oc get mcp worker The worker nodes show UPDATING as True , as well as the number of machines, the number updated, and other details: Example output NAME CONFIG UPDATED UPDATING DEGRADED MACHINECOUNT READYMACHINECOUNT UPDATEDMACHINECOUNT DEGRADEDMACHINECOUNT AGE worker rendered-worker-xyz False True False 3 2 2 0 20h When complete, the worker nodes transition back to UPDATING as False , and the UPDATEDMACHINECOUNT number matches the MACHINECOUNT : Example output NAME CONFIG UPDATED UPDATING DEGRADED MACHINECOUNT READYMACHINECOUNT UPDATEDMACHINECOUNT DEGRADEDMACHINECOUNT AGE worker rendered-worker-xyz True False False 3 3 3 0 20h Looking at a worker machine, you see that the new 8 GB max size configuration is applied to all of the workers: Example output head -n 7 /etc/containers/storage.conf [storage] driver = "overlay" runroot = "/var/run/containers/storage" graphroot = "/var/lib/containers/storage" [storage.options] additionalimagestores = [] size = "8G" Looking inside a container, you see that the root partition is now 8 GB: Example output ~ USD df -h Filesystem Size Used Available Use% Mounted on overlay 8.0G 8.0K 8.0G 0% / 5.3.4. Creating a drop-in file for the default capabilities of CRI-O You can change some of the settings associated with the OpenShift Container Platform CRI-O runtime for the nodes associated with a specific machine config pool (MCP). By using a controller custom resource (CR), you set the configuration values and add a label to match the MCP. The Machine Config Operator (MCO) then rebuilds the crio.conf and default.conf configuration files on the associated nodes with the updated values. Earlier versions of OpenShift Container Platform included specific machine configs by default. If you updated to a later version of OpenShift Container Platform, those machine configs were retained to ensure that clusters running on the same OpenShift Container Platform version have the same machine configs. You can create multiple ContainerRuntimeConfig CRs, as needed, with a limit of 10 per cluster. For the first ContainerRuntimeConfig CR, the MCO creates a machine config appended with containerruntime . With each subsequent CR, the controller creates a containerruntime machine config with a numeric suffix. For example, if you have a containerruntime machine config with a -2 suffix, the containerruntime machine config is appended with -3 . If you want to delete the machine configs, delete them in reverse order to avoid exceeding the limit. For example, delete the containerruntime-3 machine config before you delete the containerruntime-2 machine config. Note If you have a machine config with a containerruntime-9 suffix and you create another ContainerRuntimeConfig CR, a new machine config is not created, even if there are fewer than 10 containerruntime machine configs. Example of multiple ContainerRuntimeConfig CRs USD oc get ctrcfg Example output NAME AGE ctr-overlay 15m ctr-level 5m45s Example of multiple containerruntime related system configs USD cat /proc/1/status | grep Cap USD capsh --decode=<decode_CapBnd_value> 1 1 Replace <decode_CapBnd_value> with the specific value you want to decode.

Commands:
oc get mcp worker
NAME CONFIG UPDATED UPDATING DEGRADED MACHINECOUNT READYMACHINECOUNT UPDATEDMACHINECOUNT DEGRADEDMACHINECOUNT AGE worker rendered-worker-404caf3180818d8ac1f50c32f14b57c3 False True True 2 1 1 1 5h51m
oc describe mcp worker
Last Transition Time: 2021-12-20T18:54:00Z Message: Node ci-ln-j4h8nkb-72292-pxqxz-worker-a-fjks4 is reporting: "content mismatch for file \"/etc/mco-test-file\"" 1 Reason: 1 nodes are reporting degraded status on sync Status: True Type: NodeDegraded 2
oc describe node/ci-ln-j4h8nkb-72292-pxqxz-worker-a-fjks4
Annotations: cloud.network.openshift.io/egress-ipconfig: [{"interface":"nic0","ifaddr":{"ipv4":"10.0.128.0/17"},"capacity":{"ip":10}}] csi.volume.kubernetes.io/nodeid: {"pd.csi.storage.gke.io":"projects/openshift-gce-devel-ci/zones/us-central1-a/instances/ci-ln-j4h8nkb-72292-pxqxz-worker-a-fjks4"} machine.openshift.io/machine: openshift-machine-api/ci-ln-j4h8nkb-72292-pxqxz-worker-a-fjks4 machineconfiguration.openshift.io/controlPlaneTopology: HighlyAvailable machineconfiguration.openshift.io/currentConfig: rendered-worker-67bd55d0b02b0f659aef33680693a9f9 machineconfiguration.openshift.io/desiredConfig: rendered-worker-67bd55d0b02b0f659aef33680693a9f9 machineconfiguration.openshift.io/reason: content mismatch for file "/etc/mco-test-file" 1 machineconfiguration.openshift.io/state: Degraded 2
oc get machineconfigpool
NAME CONFIG UPDATED UPDATING DEGRADED MACHINECOUNT READYMACHINECOUNT UPDATEDMACHINECOUNT DEGRADEDMACHINECOUNT AGE master rendered-master-06c9c4... True False False 3 3 3 0 4h42m worker rendered-worker-f4b64... False True False 3 2 2 0 4h42m
NAME CONFIG UPDATED UPDATING DEGRADED MACHINECOUNT READYMACHINECOUNT UPDATEDMACHINECOUNT DEGRADEDMACHINECOUNT AGE master rendered-master-06c9c4... True False False 3 3 3 0 4h42m worker rendered-worker-c1b41a... False True False 3 2 3 0 4h42m
oc describe mcp worker
Degraded Machine Count: 0 Machine Count: 3 Observed Generation: 2 Ready Machine Count: 3 Unavailable Machine Count: 0 Updated Machine Count: 3 Events: <none>
Degraded Machine Count: 0 Machine Count: 3 Observed Generation: 2 Ready Machine Count: 2 Unavailable Machine Count: 1 Updated Machine Count: 3
oc get machineconfigs
NAME GENERATEDBYCONTROLLER IGNITIONVERSION AGE 00-master 2c9371fbb673b97a6fe8b1c52... 3.2.0 5h18m 00-worker 2c9371fbb673b97a6fe8b1c52... 3.2.0 5h18m 01-master-container-runtime 2c9371fbb673b97a6fe8b1c52... 3.2.0 5h18m 01-master-kubelet 2c9371fbb673b97a6fe8b1c52... 3.2.0 5h18m rendered-master-dde... 2c9371fbb673b97a6fe8b1c52... 3.2.0 5h18m rendered-worker-fde... 2c9371fbb673b97a6fe8b1c52... 3.2.0 5h18m
oc describe machineconfigs 01-master-kubelet
Name: 01-master-kubelet Spec: Config: Ignition: Version: 3.2.0 Storage: Files: Contents: Source: data:, Mode: 420 Overwrite: true Path: /etc/kubernetes/cloud.conf Contents: Source: data:,kind%3A%20KubeletConfiguration%0AapiVersion%3A%20kubelet.config.k8s.io%2Fv1beta1%0Aauthentication%3A%0A%20%20x509%3A%0A%20%20%20%20clientCAFile%3A%20%2Fetc%2Fkubernetes%2Fkubelet-ca.crt%0A%20%20anonymous Mode: 420 Overwrite: true Path: /etc/kubernetes/kubelet.conf Systemd: Units: Contents: [Unit] Description=Kubernetes Kubelet Wants=rpc-statd.service network-online.target crio.service After=network-online.target crio.service ExecStart=/usr/bin/hyperkube kubelet --config=/etc/kubernetes/kubelet.conf \
oc delete -f ./myconfig.yaml
variant: openshift version: 4.13.0 metadata: name: 99-worker-chrony 1 labels: machineconfiguration.openshift.io/role: worker 2 storage: files: - path: /etc/chrony.conf mode: 0644 3 overwrite: true contents: inline: | pool 0.rhel.pool.ntp.org iburst 4 driftfile /var/lib/chrony/drift makestep 1.0 3 rtcsync logdir /var/log/chrony
butane 99-worker-chrony.bu -o 99-worker-chrony.yaml
oc apply -f ./99-worker-chrony.yaml
apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfig metadata: labels: machineconfiguration.openshift.io/role: <node_role> 1 name: disable-chronyd spec: config: ignition: version: 3.2.0 systemd: units: - contents: | [Unit] Description=NTP client/server Documentation=man:chronyd(8) man:chrony.conf(5) After=ntpdate.service sntp.service ntpd.service Conflicts=ntpd.service systemd-timesyncd.service ConditionCapability=CAP_SYS_TIME [Service] Type=forking PIDFile=/run/chrony/chronyd.pid EnvironmentFile=-/etc/sysconfig/chronyd ExecStart=/usr/sbin/chronyd USDOPTIONS ExecStartPost=/usr/libexec/chrony-helper update-daemon PrivateTmp=yes ProtectHome=yes ProtectSystem=full [Install] WantedBy=multi-user.target enabled: false name: "chronyd.service"
oc create -f disable-chronyd.yaml
oc get MachineConfig
NAME GENERATEDBYCONTROLLER IGNITIONVERSION AGE 00-master 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 00-worker 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-master-container-runtime 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-master-kubelet 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-worker-container-runtime 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-worker-kubelet 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 99-master-generated-registries 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 99-master-ssh 3.2.0 40m 99-worker-generated-registries 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 99-worker-ssh 3.2.0 40m rendered-master-23e785de7587df95a4b517e0647e5ab7 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m rendered-worker-5d596d9293ca3ea80c896a1191735bb1 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m
apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfig metadata: labels: machineconfiguration.openshift.io/role: worker 1 name: 05-worker-kernelarg-selinuxpermissive 2 spec: kernelArguments: - enforcing=0 3
oc create -f 05-worker-kernelarg-selinuxpermissive.yaml
oc get MachineConfig
NAME GENERATEDBYCONTROLLER IGNITIONVERSION AGE 00-master 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 00-worker 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-master-container-runtime 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-master-kubelet 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-worker-container-runtime 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-worker-kubelet 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 05-worker-kernelarg-selinuxpermissive 3.2.0 105s 99-master-generated-registries 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 99-master-ssh 3.2.0 40m 99-worker-generated-registries 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 99-worker-ssh 3.2.0 40m rendered-master-23e785de7587df95a4b517e0647e5ab7 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m rendered-worker-5d596d9293ca3ea80c896a1191735bb1 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m
oc get nodes
NAME STATUS ROLES AGE VERSION ip-10-0-136-161.ec2.internal Ready worker 28m v1.26.0 ip-10-0-136-243.ec2.internal Ready master 34m v1.26.0 ip-10-0-141-105.ec2.internal Ready,SchedulingDisabled worker 28m v1.26.0 ip-10-0-142-249.ec2.internal Ready master 34m v1.26.0 ip-10-0-153-11.ec2.internal Ready worker 28m v1.26.0 ip-10-0-153-150.ec2.internal Ready master 34m v1.26.0
oc debug node/ip-10-0-141-105.ec2.internal
Starting pod/ip-10-0-141-105ec2internal-debug To use host binaries, run `chroot /host` sh-4.2# cat /host/proc/cmdline BOOT_IMAGE=/ostree/rhcos-... console=tty0 console=ttyS0,115200n8 rootflags=defaults,prjquota rw root=UUID=fd0... ostree=/ostree/boot.0/rhcos/16 coreos.oem.id=qemu coreos.oem.id=ec2 ignition.platform.id=ec2 enforcing=0 sh-4.2# exit
apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfig metadata: labels: machineconfiguration.openshift.io/role: "master" name: 99-master-kargs-mpath spec: kernelArguments: - 'rd.multipath=default' - 'root=/dev/disk/by-label/dm-mpath-root'
apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfig metadata: labels: machineconfiguration.openshift.io/role: "worker" name: 99-worker-kargs-mpath spec: kernelArguments: - 'rd.multipath=default' - 'root=/dev/disk/by-label/dm-mpath-root'
oc create -f ./99-worker-kargs-mpath.yaml
oc get MachineConfig
NAME GENERATEDBYCONTROLLER IGNITIONVERSION AGE 00-master 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 00-worker 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-master-container-runtime 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-master-kubelet 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-worker-container-runtime 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 01-worker-kubelet 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 99-master-generated-registries 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 99-master-ssh 3.2.0 40m 99-worker-generated-registries 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m 99-worker-kargs-mpath 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 105s 99-worker-ssh 3.2.0 40m rendered-master-23e785de7587df95a4b517e0647e5ab7 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m rendered-worker-5d596d9293ca3ea80c896a1191735bb1 52dd3ba6a9a527fc3ab42afac8d12b693534c8c9 3.2.0 33m
oc get nodes
NAME STATUS ROLES AGE VERSION ip-10-0-136-161.ec2.internal Ready worker 28m v1.26.0 ip-10-0-136-243.ec2.internal Ready master 34m v1.26.0 ip-10-0-141-105.ec2.internal Ready,SchedulingDisabled worker 28m v1.26.0 ip-10-0-142-249.ec2.internal Ready master 34m v1.26.0 ip-10-0-153-11.ec2.internal Ready worker 28m v1.26.0 ip-10-0-153-150.ec2.internal Ready master 34m v1.26.0
oc debug node/ip-10-0-141-105.ec2.internal
Starting pod/ip-10-0-141-105ec2internal-debug To use host binaries, run `chroot /host` sh-4.2# cat /host/proc/cmdline rd.multipath=default root=/dev/disk/by-label/dm-mpath-root sh-4.2# exit
cat << EOF > 99-worker-realtime.yaml apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfig metadata: labels: machineconfiguration.openshift.io/role: "worker" name: 99-worker-realtime spec: kernelType: realtime EOF
oc create -f 99-worker-realtime.yaml
oc get nodes
NAME STATUS ROLES AGE VERSION ip-10-0-143-147.us-east-2.compute.internal Ready worker 103m v1.26.0 ip-10-0-146-92.us-east-2.compute.internal Ready worker 101m v1.26.0 ip-10-0-169-2.us-east-2.compute.internal Ready worker 102m v1.26.0
oc debug node/ip-10-0-143-147.us-east-2.compute.internal
Starting pod/ip-10-0-143-147us-east-2computeinternal-debug To use host binaries, run `chroot /host` sh-4.4# uname -a Linux <worker_node> 4.18.0-147.3.1.rt24.96.el8_1.x86_64 #1 SMP PREEMPT RT Wed Nov 27 18:29:55 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
oc delete -f 99-worker-realtime.yaml
variant: openshift version: 4.13.0 metadata: name: 40-worker-custom-journald labels: machineconfiguration.openshift.io/role: worker storage: files: - path: /etc/systemd/journald.conf mode: 0644 overwrite: true contents: inline: | # Disable rate limiting RateLimitInterval=1s RateLimitBurst=10000 Storage=volatile Compress=no MaxRetentionSec=30s
butane 40-worker-custom-journald.bu -o 40-worker-custom-journald.yaml
oc apply -f 40-worker-custom-journald.yaml
oc get machineconfigpool NAME CONFIG UPDATED UPDATING DEGRADED MACHINECOUNT READYMACHINECOUNT UPDATEDMACHINECOUNT DEGRADEDMACHINECOUNT AGE master rendered-master-35 True False False 3 3 3 0 34m worker rendered-worker-d8 False True False 3 1 1 0 34m
oc get node | grep worker ip-10-0-0-1.us-east-2.compute.internal Ready worker 39m v0.0.0-master+USDFormat:%hUSD oc debug node/ip-10-0-0-1.us-east-2.compute.internal Starting pod/ip-10-0-141-142us-east-2computeinternal-debug sh-4.2# chroot /host sh-4.4# cat /etc/systemd/journald.conf Disable rate limiting RateLimitInterval=1s RateLimitBurst=10000 Storage=volatile Compress=no MaxRetentionSec=30s sh-4.4# exit
cat << EOF > 80-extensions.yaml apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfig metadata: labels: machineconfiguration.openshift.io/role: worker name: 80-worker-extensions spec: config: ignition: version: 3.2.0 extensions: - usbguard EOF
oc create -f 80-extensions.yaml
oc get machineconfig 80-worker-extensions
NAME GENERATEDBYCONTROLLER IGNITIONVERSION AGE 80-worker-extensions 3.2.0 57s
oc get machineconfigpool
NAME CONFIG UPDATED UPDATING DEGRADED MACHINECOUNT READYMACHINECOUNT UPDATEDMACHINECOUNT DEGRADEDMACHINECOUNT AGE master rendered-master-35 True False False 3 3 3 0 34m worker rendered-worker-d8 False True False 3 1 1 0 34m
oc get node | grep worker
NAME STATUS ROLES AGE VERSION ip-10-0-169-2.us-east-2.compute.internal Ready worker 102m v1.26.0
oc debug node/ip-10-0-169-2.us-east-2.compute.internal
To use host binaries, run `chroot /host` sh-4.4# chroot /host sh-4.4# rpm -q usbguard usbguard-0.7.4-4.el8.x86_64.rpm
variant: openshift version: 4.13.0 metadata: labels: machineconfiguration.openshift.io/role: worker name: 98-worker-firmware-blob storage: files: - path: /var/lib/firmware/<package_name> 1 contents: local: <package_name> 2 mode: 0644 3 openshift: kernel_arguments: - 'firmware_class.path=/var/lib/firmware' 4
butane 98-worker-firmware-blob.bu -o 98-worker-firmware-blob.yaml --files-dir <directory_including_package_name>
oc apply -f 98-worker-firmware-blob.yaml
apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfigPool metadata: name: infra spec: machineConfigSelector: matchExpressions: - {key: machineconfiguration.openshift.io/role, operator: In, values: [worker,infra]}
oc get kubeletconfig
NAME AGE set-kubelet-config 15m
oc get mc | grep kubelet
99-worker-generated-kubelet-1 b5c5119de007945b6fe6fb215db3b8e2ceb12511 3.2.0 26m
oc describe machineconfigpool <name>
oc describe machineconfigpool worker
apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfigPool metadata: creationTimestamp: 2019-02-08T14:52:39Z generation: 1 labels: custom-kubelet: set-kubelet-config 1
oc label machineconfigpool worker custom-kubelet=set-kubelet-config
oc get machineconfig
oc describe node <node_name>
oc describe node ci-ln-5grqprb-f76d1-ncnqq-worker-a-mdv94
Allocatable: attachable-volumes-aws-ebs: 25 cpu: 3500m hugepages-1Gi: 0 hugepages-2Mi: 0 memory: 15341844Ki pods: 250
apiVersion: machineconfiguration.openshift.io/v1 kind: KubeletConfig metadata: name: set-kubelet-config spec: machineConfigPoolSelector: matchLabels: custom-kubelet: set-kubelet-config 1 kubeletConfig: 2 podPidsLimit: 8192 containerLogMaxSize: 50Mi maxPods: 500
apiVersion: machineconfiguration.openshift.io/v1 kind: KubeletConfig metadata: name: set-kubelet-config spec: machineConfigPoolSelector: matchLabels: custom-kubelet: set-kubelet-config kubeletConfig: maxPods: <pod_count> kubeAPIBurst: <burst_rate> kubeAPIQPS: <QPS>
oc label machineconfigpool worker custom-kubelet=set-kubelet-config
oc create -f change-maxPods-cr.yaml
oc get kubeletconfig
NAME AGE set-kubelet-config 15m
oc describe node <node_name>
Allocatable: attachable-volumes-gce-pd: 127 cpu: 3500m ephemeral-storage: 123201474766 hugepages-1Gi: 0 hugepages-2Mi: 0 memory: 14225400Ki pods: 500 1
oc get kubeletconfigs set-kubelet-config -o yaml
spec: kubeletConfig: containerLogMaxSize: 50Mi maxPods: 500 podPidsLimit: 8192 machineConfigPoolSelector: matchLabels: custom-kubelet: set-kubelet-config status: conditions: - lastTransitionTime: "2021-06-30T17:04:07Z" message: Success status: "True" type: Success
oc get ctrcfg
NAME AGE ctr-overlay 15m ctr-level 5m45s
oc get mc | grep container
01-master-container-runtime b5c5119de007945b6fe6fb215db3b8e2ceb12511 3.2.0 57m 01-worker-container-runtime b5c5119de007945b6fe6fb215db3b8e2ceb12511 3.2.0 57m 99-worker-generated-containerruntime b5c5119de007945b6fe6fb215db3b8e2ceb12511 3.2.0 26m 99-worker-generated-containerruntime-1 b5c5119de007945b6fe6fb215db3b8e2ceb12511 3.2.0 17m 99-worker-generated-containerruntime-2 b5c5119de007945b6fe6fb215db3b8e2ceb12511 3.2.0 7m26s
apiVersion: machineconfiguration.openshift.io/v1 kind: ContainerRuntimeConfig metadata: name: overlay-size spec: machineConfigPoolSelector: matchLabels: pools.operator.machineconfiguration.openshift.io/worker: '' 1 containerRuntimeConfig: logLevel: debug 2 overlaySize: 8G 3 defaultRuntime: "crun" 4
apiVersion: machineconfiguration.openshift.io/v1 kind: ContainerRuntimeConfig metadata: name: overlay-size spec: machineConfigPoolSelector: matchLabels: pools.operator.machineconfiguration.openshift.io/worker: '' 1 containerRuntimeConfig: 2 logLevel: debug overlaySize: 8G
oc create -f <file_name>.yaml
oc get ContainerRuntimeConfig
NAME AGE overlay-size 3m19s
oc get machineconfigs | grep containerrun
99-worker-generated-containerruntime 2c9371fbb673b97a6fe8b1c52691999ed3a1bfc2 3.2.0 31s
oc get mcp worker
NAME CONFIG UPDATED UPDATING DEGRADED MACHINECOUNT READYMACHINECOUNT UPDATEDMACHINECOUNT DEGRADEDMACHINECOUNT AGE worker rendered-worker-169 False True False 3 1 1 0 9h
oc debug node/<node_name>
sh-4.4# chroot /host
sh-4.4# crio config | grep 'log_level'
log_level = "debug"
sh-4.4# head -n 7 /etc/containers/storage.conf
[storage] driver = "overlay" runroot = "/var/run/containers/storage" graphroot = "/var/lib/containers/storage" [storage.options] additionalimagestores = [] size = "8G"
apiVersion: machineconfiguration.openshift.io/v1 kind: ContainerRuntimeConfig metadata: name: overlay-size spec: machineConfigPoolSelector: matchLabels: custom-crio: overlay-size containerRuntimeConfig: logLevel: debug overlaySize: 8G
oc apply -f overlaysize.yml
oc edit machineconfigpool worker
apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfigPool metadata: creationTimestamp: "2020-07-09T15:46:34Z" generation: 3 labels: custom-crio: overlay-size machineconfiguration.openshift.io/mco-built-in: ""
oc get machineconfigs
99-worker-generated-containerruntime 4173030d89fbf4a7a0976d1665491a4d9a6e54f1 3.2.0 7m42s rendered-worker-xyz 4173030d89fbf4a7a0976d1665491a4d9a6e54f1 3.2.0 7m36s
oc get mcp worker
NAME CONFIG UPDATED UPDATING DEGRADED MACHINECOUNT READYMACHINECOUNT UPDATEDMACHINECOUNT DEGRADEDMACHINECOUNT AGE worker rendered-worker-xyz False True False 3 2 2 0 20h
NAME CONFIG UPDATED UPDATING DEGRADED MACHINECOUNT READYMACHINECOUNT UPDATEDMACHINECOUNT DEGRADEDMACHINECOUNT AGE worker rendered-worker-xyz True False False 3 3 3 0 20h
head -n 7 /etc/containers/storage.conf [storage] driver = "overlay" runroot = "/var/run/containers/storage" graphroot = "/var/lib/containers/storage" [storage.options] additionalimagestores = [] size = "8G"
~ USD df -h Filesystem Size Used Available Use% Mounted on overlay 8.0G 8.0K 8.0G 0% /
oc get ctrcfg
NAME AGE ctr-overlay 15m ctr-level 5m45s
cat /proc/1/status | grep Cap
capsh --decode=<decode_CapBnd_value> 1