Chapter 3. Post-installation 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. 3.1. Understanding the Machine Config Operator 3.1.1. Machine Config Operator Purpose The Machine Config Operator manages and applies configuration and updates of the base operating system and container runtime, including everything between the kernel and kubelet. There are four components: machine-config-server : Provides Ignition configuration to new machines joining the cluster. machine-config-controller : Coordinates the upgrade of machines to the desired configurations defined by a MachineConfig object. Options are provided to control the upgrade for sets of machines individually. machine-config-daemon : Applies new machine configuration during update. Validates and verifies the state of the machine to the requested machine configuration. machine-config : Provides a complete source of machine configuration at installation, first start up, and updates for a machine. Important Currently, there is no supported way to block or restrict the machine config server endpoint. The machine config server must be exposed to the network so that newly-provisioned machines, which have no existing configuration or state, are able to fetch their configuration. In this model, the root of trust is the certificate signing requests (CSR) endpoint, which is where the kubelet sends its certificate signing request for approval to join the cluster. Because of this, machine configs should not be used to distribute sensitive information, such as secrets and certificates. To ensure that the machine config server endpoints, ports 22623 and 22624, are secured in bare metal scenarios, customers must configure proper network policies. Additional resources About the OpenShift SDN network plugin . Project openshift-machine-config-operator 3.1.2. 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 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 MCO, machine configs, and how they are used: 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. 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 post-installation 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. 3.1.2.1. 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 post-installation. Important Changing SSH keys via machine configs is only supported for the core user. 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. fips : Enable FIPS mode. FIPS should be set at installation-time setting and not a post-installation procedure. Important The use of FIPS Validated / Modules in Process cryptographic libraries is only supported on OpenShift Container Platform deployments on the x86_64 architecture. 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 post-installation 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. 3.1.2.2. Project See the openshift-machine-config-operator GitHub site for details. 3.1.3. 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. 3.2. 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. 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. 3.2.1. 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: 4.9.0 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 3.2.2. 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 3.2.3. 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: 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. 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. 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: config: ignition: version: 3.2.0 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 v1.22.1 ip-10-0-136-243.ec2.internal Ready master 34m v1.22.1 ip-10-0-141-105.ec2.internal Ready,SchedulingDisabled worker 28m v1.22.1 ip-10-0-142-249.ec2.internal Ready master 34m v1.22.1 ip-10-0-153-11.ec2.internal Ready worker 28m v1.22.1 ip-10-0-153-150.ec2.internal Ready master 34m v1.22.1 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. 3.2.4. 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. Post-installation 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 4.8 or higher. 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 with kernel arguments on RHCOS" in the Installing on bare metal documentation. Important On IBM Z and 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 LinuxONE . Prerequisites You have a running OpenShift Container Platform cluster that uses version 4.7 or later. 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 post-installation 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 post-installation 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 v1.22.1 ip-10-0-136-243.ec2.internal Ready master 34m v1.22.1 ip-10-0-141-105.ec2.internal Ready,SchedulingDisabled worker 28m v1.22.1 ip-10-0-142-249.ec2.internal Ready master 34m v1.22.1 ip-10-0-153-11.ec2.internal Ready worker 28m v1.22.1 ip-10-0-153-150.ec2.internal Ready master 34m v1.22.1 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. 3.2.5. 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, 4.9 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 v1.22.1 ip-10-0-146-92.us-east-2.compute.internal Ready worker 101m v1.22.1 ip-10-0-169-2.us-east-2.compute.internal Ready worker 102m v1.22.1 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 3.2.6. 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: 4.9.0 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 3.2.7. 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 extension is available: usbguard : Adding the usbguard extension protects RHCOS systems from attacks from intrusive USB devices. See USBGuard for details. 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 v1.22.1 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 3.2.8. 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: 4.9.0 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 3.3. 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. 3.3.1. 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: Create one KubeletConfig 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 of the pools, you need only one KubeletConfig CR for all of the pools. 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. 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 . 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-max-pods 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 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-max-pods 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-max-pods 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 Set the maximum pods per node on the worker nodes by creating a custom resource file that contains the kubelet configuration: apiVersion: machineconfiguration.openshift.io/v1 kind: KubeletConfig metadata: name: set-max-pods spec: machineConfigPoolSelector: matchLabels: custom-kubelet: set-max-pods 1 kubeletConfig: maxPods: 500 2 1 Enter the label from the machine config pool. 2 Add the kubelet configuration. In this example, 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-max-pods spec: machineConfigPoolSelector: matchLabels: custom-kubelet: set-max-pods 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=large-pods Create the KubeletConfig object: USD oc create -f change-maxPods-cr.yaml Verify that the KubeletConfig object is created: USD oc get kubeletconfig Example output NAME AGE set-max-pods 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-max-pods -o yaml This should show a status of True and type:Success , as shown in the following example: spec: kubeletConfig: maxPods: 500 machineConfigPoolSelector: matchLabels: custom-kubelet: set-max-pods status: conditions: - lastTransitionTime: "2021-06-30T17:04:07Z" message: Success status: "True" type: Success 3.3.2. 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: PIDs limit : The pidsLimit parameter sets the CRI-O pids_limit parameter, which is maximum number of processes allowed in a container. The default is 1024 ( pids_limit = 1024 ). 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. Maximum log size : The logSizeMax parameter sets the CRI-O log_size_max parameter, which is the maximum size allowed for the container log file. The default is unlimited ( log_size_max = -1 ). If set to a positive number, it must be at least 8192 to not be smaller than the ConMon read buffer. ConMon is a program that monitors communications between a container manager (such as Podman or CRI-O) and the OCI runtime (such as runc or crun) for a single container. 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-pid 24m 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 raises the pids_limit to 2048, sets the log_level to debug , sets the overlay size to 8 GB, and sets the log_size_max to unlimited: 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: pidsLimit: 2048 2 logLevel: debug 3 overlaySize: 8G 4 logSizeMax: "-1" 5 1 Specifies the machine config pool label. 2 Optional: Specifies the maximum number of processes allowed in a container. 3 Optional: Specifies the level of verbosity for log messages. 4 Optional: Specifies the maximum size of a container image. 5 Optional: Specifies the maximum size allowed for the container log file. If set to a positive number, it must be at least 8192. 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 pidsLimit: 2048 logLevel: debug overlaySize: 8G logSizeMax: "-1" 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 | egrep 'log_level|pids_limit|log_size_max' Example output pids_limit = 2048 log_size_max = -1 log_level = "debug" Verify the changes in the `storage.conf`file: sh-4.4# head -n 7 /etc/containers/storage.conf Example output 3.3.3. 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 and PID limit, 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: pidsLimit: 2048 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% /

Commands:
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: 4.9.0 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: config: ignition: version: 3.2.0 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 v1.22.1 ip-10-0-136-243.ec2.internal Ready master 34m v1.22.1 ip-10-0-141-105.ec2.internal Ready,SchedulingDisabled worker 28m v1.22.1 ip-10-0-142-249.ec2.internal Ready master 34m v1.22.1 ip-10-0-153-11.ec2.internal Ready worker 28m v1.22.1 ip-10-0-153-150.ec2.internal Ready master 34m v1.22.1
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 v1.22.1 ip-10-0-136-243.ec2.internal Ready master 34m v1.22.1 ip-10-0-141-105.ec2.internal Ready,SchedulingDisabled worker 28m v1.22.1 ip-10-0-142-249.ec2.internal Ready master 34m v1.22.1 ip-10-0-153-11.ec2.internal Ready worker 28m v1.22.1 ip-10-0-153-150.ec2.internal Ready master 34m v1.22.1
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 v1.22.1 ip-10-0-146-92.us-east-2.compute.internal Ready worker 101m v1.22.1 ip-10-0-169-2.us-east-2.compute.internal Ready worker 102m v1.22.1
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: 4.9.0 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 v1.22.1
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: 4.9.0 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
oc get kubeletconfig
NAME AGE set-max-pods 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-max-pods 1
oc label machineconfigpool worker custom-kubelet=set-max-pods
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-max-pods spec: machineConfigPoolSelector: matchLabels: custom-kubelet: set-max-pods 1 kubeletConfig: maxPods: 500 2
apiVersion: machineconfiguration.openshift.io/v1 kind: KubeletConfig metadata: name: set-max-pods spec: machineConfigPoolSelector: matchLabels: custom-kubelet: set-max-pods kubeletConfig: maxPods: <pod_count> kubeAPIBurst: <burst_rate> kubeAPIQPS: <QPS>
oc label machineconfigpool worker custom-kubelet=large-pods
oc create -f change-maxPods-cr.yaml
oc get kubeletconfig
NAME AGE set-max-pods 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-max-pods -o yaml
spec: kubeletConfig: maxPods: 500 machineConfigPoolSelector: matchLabels: custom-kubelet: set-max-pods status: conditions: - lastTransitionTime: "2021-06-30T17:04:07Z" message: Success status: "True" type: Success
oc get ctrcfg
NAME AGE ctr-pid 24m 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: pidsLimit: 2048 2 logLevel: debug 3 overlaySize: 8G 4 logSizeMax: "-1" 5
apiVersion: machineconfiguration.openshift.io/v1 kind: ContainerRuntimeConfig metadata: name: overlay-size spec: machineConfigPoolSelector: matchLabels: pools.operator.machineconfiguration.openshift.io/worker: '' 1 containerRuntimeConfig: 2 pidsLimit: 2048 logLevel: debug overlaySize: 8G logSizeMax: "-1"
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 | egrep 'log_level|pids_limit|log_size_max'
pids_limit = 2048 log_size_max = -1 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: pidsLimit: 2048 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% /