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Post-installation configuration
Chapter 3. Post-installation machine configuration tasks

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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
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3.1.1. Machine Config Operator
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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.

Project

openshift-machine-config-operator

3.1.2. Machine config overview
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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 (also known as the master 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?
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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
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See the openshift-machine-config-operator GitHub site for details.

3.1.3. Checking machine config pool status
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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:
```
$ 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 previous 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: :

$ 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:

$ 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:

$ 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:

$ 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 previous 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
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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
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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: 4.8.0
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:
```
$ 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:
  $ oc apply -f ./99-worker-chrony.yaml

3.2.2. Adding kernel arguments to nodes
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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:

$ 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


  name: 05-worker-kernelarg-selinuxpermissive


spec:
  config:
    ignition:
      version: 3.2.0
  kernelArguments:
    - enforcing=0

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:

$ oc create -f 05-worker-kernelarg-selinuxpermissive.yaml

Check the machine configs to see that the new one was added:

$ 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:

$ oc get nodes

Example output

NAME                           STATUS                     ROLES    AGE   VERSION
ip-10-0-136-161.ec2.internal   Ready                      worker   28m   v1.21.0
ip-10-0-136-243.ec2.internal   Ready                      master   34m   v1.21.0
ip-10-0-141-105.ec2.internal   Ready,SchedulingDisabled   worker   28m   v1.21.0
ip-10-0-142-249.ec2.internal   Ready                      master   34m   v1.21.0
ip-10-0-153-11.ec2.internal    Ready                      worker   28m   v1.21.0
ip-10-0-153-150.ec2.internal   Ready                      master   34m   v1.21.0

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):

$ 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.

3.2.3. Enabling multipathing with kernel arguments on RHCOS
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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.

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:
```
$ oc create -f ./99-worker-kargs-mpath.yaml
```

Check the machine configs to see that the new one was added:

$ 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:

$ oc get nodes

Example output

NAME                           STATUS                     ROLES    AGE   VERSION
ip-10-0-136-161.ec2.internal   Ready                      worker   28m   v1.20.0
ip-10-0-136-243.ec2.internal   Ready                      master   34m   v1.20.0
ip-10-0-141-105.ec2.internal   Ready,SchedulingDisabled   worker   28m   v1.20.0
ip-10-0-142-249.ec2.internal   Ready                      master   34m   v1.20.0
ip-10-0-153-11.ec2.internal    Ready                      worker   28m   v1.20.0
ip-10-0-153-150.ec2.internal   Ready                      master   34m   v1.20.0

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):

$ 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.

3.2.4. Adding a real-time kernel to nodes
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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, 4.8 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:

$ 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:
```
$ 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:

$ oc get nodes

Example output

NAME                                        STATUS  ROLES    AGE   VERSION
ip-10-0-143-147.us-east-2.compute.internal  Ready   worker   103m  v1.21.0
ip-10-0-146-92.us-east-2.compute.internal   Ready   worker   101m  v1.21.0
ip-10-0-169-2.us-east-2.compute.internal    Ready   worker   102m  v1.21.0

$ 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:

$ oc delete -f 99-worker-realtime.yaml

3.2.5. Configuring journald settings
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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: 4.8.0
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:

$ butane 40-worker-custom-journald.bu -o 40-worker-custom-journald.yaml

Apply the machine config to the pool:

$ 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:

$ 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:

$ oc get node | grep worker
ip-10-0-0-1.us-east-2.compute.internal   Ready    worker   39m   v0.0.0-master+$Format:%h$
$ 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

3.2.6. Adding extensions to RHCOS
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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.

$ 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:
```
$ oc create -f 80-extensions.yaml
```
This sets all worker nodes to have rpm packages for
```
usbguard
```
installed.

Check that the extensions were applied:

$ 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:

$ 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:

$ 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  v1.18.3

$ 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

3.2.7. Loading custom firmware blobs in the machine config manifest
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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:
```
$ 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:
  $ 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.

3.3. Configuring MCO-related custom resources
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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
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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 next
```
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

$ oc get kubeletconfig

NAME                AGE
set-max-pods        15m

Example showing a KubeletConfig machine config

$ 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:

$ oc describe machineconfigpool <name>

For example:

$ 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: If a label has been added it appears under labels.

If the label is not present, add a key/value pair:

$ oc label machineconfigpool worker custom-kubelet=set-max-pods

Procedure

View the available machine configuration objects that you can select:
```
$ 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:

$ oc describe node <node_name>

For example:

$ 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>
1. Update the machine config pool for workers with the label:
  $ oc label machineconfigpool worker custom-kubelet=large-pods
2. Create the
  KubeletConfig
  object:
  $ oc create -f change-maxPods-cr.yaml
3. Verify that the
  KubeletConfig
  object is created:
  $ 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:
```
$ 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: In this example, the pods parameter should report the value you set in the KubeletConfig object.

Verify the change in the

KubeletConfig

object:

$ oc get kubeletconfigs set-max-pods -o yaml

This should show a

status: "True"

and

type:Success

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
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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 next

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

$ oc get ctrcfg

Example output

NAME         AGE
ctr-pid      24m
ctr-overlay  15m
ctr-level    5m45s

Example showing multiple containerruntime machine configs

$ 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

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: ''


 containerRuntimeConfig:
   pidsLimit: 2048


   logLevel: debug


   overlaySize: 8G


   logSizeMax: "-1"

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: ''


 containerRuntimeConfig:


   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:

$ oc create -f <file_name>.yaml

Verify that the CR is created:

$ oc get ContainerRuntimeConfig

Example output

NAME           AGE
overlay-size   3m19s

Check that a new

containerruntime

machine config is created:

$ 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:

$ 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

$ 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

[storage]
  driver = "overlay"
  runroot = "/var/run/containers/storage"
  graphroot = "/var/lib/containers/storage"
  [storage.options]
    additionalimagestores = []
    size = "8G"

3.3.3. Setting the default maximum container root partition size for Overlay with CRI-O
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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:
```
$ oc apply -f overlaysize.yml
```
To apply the new CRI-O configuration to your worker nodes, edit the worker machine config pool:
```
$ 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:

$ 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:

$ oc get mcp worker

The worker nodes show

UPDATING

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

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

~ $ df -h
Filesystem                Size      Used Available Use% Mounted on
overlay                   8.0G      8.0K      8.0G   0% /

Este contenido no está disponible en el idioma seleccionado.

Chapter 3. Post-installation machine configuration tasks

3.1. Understanding the Machine Config Operator
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3.1.1. Machine Config Operator
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Purpose

Project

3.1.2. Machine config overview
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3.1.2.1. What can you change with machine configs?
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3.1.2.2. Project
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3.1.3. Checking machine config pool status
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3.2. Using MachineConfig objects to configure nodes
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3.2.1. Configuring chrony time service
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3.2.2. Adding kernel arguments to nodes
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3.2.3. Enabling multipathing with kernel arguments on RHCOS
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3.2.4. Adding a real-time kernel to nodes
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3.2.5. Configuring journald settings
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3.2.6. Adding extensions to RHCOS
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3.2.7. Loading custom firmware blobs in the machine config manifest
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3.3. Configuring MCO-related custom resources
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3.3.1. Creating a KubeletConfig CRD to edit kubelet parameters
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3.3.2. Creating a ContainerRuntimeConfig CR to edit CRI-O parameters
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3.3.3. Setting the default maximum container root partition size for Overlay with CRI-O
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Comunidades

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Este contenido no está disponible en el idioma seleccionado.

Chapter 3. Post-installation machine configuration tasks

3.1. Understanding the Machine Config OperatorCopiar enlaceEnlace copiado en el portapapeles!

3.1.1. Machine Config OperatorCopiar enlaceEnlace copiado en el portapapeles!

Purpose

Project

3.1.2. Machine config overviewCopiar enlaceEnlace copiado en el portapapeles!

3.1.2.1. What can you change with machine configs?Copiar enlaceEnlace copiado en el portapapeles!

3.1.2.2. ProjectCopiar enlaceEnlace copiado en el portapapeles!

3.1.3. Checking machine config pool statusCopiar enlaceEnlace copiado en el portapapeles!

3.2. Using MachineConfig objects to configure nodesCopiar enlaceEnlace copiado en el portapapeles!

3.2.1. Configuring chrony time serviceCopiar enlaceEnlace copiado en el portapapeles!

3.2.2. Adding kernel arguments to nodesCopiar enlaceEnlace copiado en el portapapeles!

3.2.3. Enabling multipathing with kernel arguments on RHCOSCopiar enlaceEnlace copiado en el portapapeles!

3.2.4. Adding a real-time kernel to nodesCopiar enlaceEnlace copiado en el portapapeles!

3.2.5. Configuring journald settingsCopiar enlaceEnlace copiado en el portapapeles!

3.2.6. Adding extensions to RHCOSCopiar enlaceEnlace copiado en el portapapeles!

3.2.7. Loading custom firmware blobs in the machine config manifestCopiar enlaceEnlace copiado en el portapapeles!

3.3. Configuring MCO-related custom resourcesCopiar enlaceEnlace copiado en el portapapeles!

3.3.1. Creating a KubeletConfig CRD to edit kubelet parametersCopiar enlaceEnlace copiado en el portapapeles!

3.3.2. Creating a ContainerRuntimeConfig CR to edit CRI-O parametersCopiar enlaceEnlace copiado en el portapapeles!

3.3.3. Setting the default maximum container root partition size for Overlay with CRI-OCopiar enlaceEnlace copiado en el portapapeles!

Aprender

Pruebe, compre y venda

Comunidades

Acerca de la documentación de Red Hat

Hacer que el código abierto sea más inclusivo

Acerca de Red Hat

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Red Hat legal and privacy links

Red Hat legal and privacy links

3.1. Understanding the Machine Config Operator
Copiar enlace

3.1.1. Machine Config Operator
Copiar enlace

3.1.2. Machine config overview
Copiar enlace

3.1.2.1. What can you change with machine configs?
Copiar enlace

3.1.2.2. Project
Copiar enlace

3.1.3. Checking machine config pool status
Copiar enlace

3.2. Using MachineConfig objects to configure nodes
Copiar enlace

3.2.1. Configuring chrony time service
Copiar enlace

3.2.2. Adding kernel arguments to nodes
Copiar enlace

3.2.3. Enabling multipathing with kernel arguments on RHCOS
Copiar enlace

3.2.4. Adding a real-time kernel to nodes
Copiar enlace

3.2.5. Configuring journald settings
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3.2.6. Adding extensions to RHCOS
Copiar enlace

3.2.7. Loading custom firmware blobs in the machine config manifest
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3.3. Configuring MCO-related custom resources
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3.3.1. Creating a KubeletConfig CRD to edit kubelet parameters
Copiar enlace

3.3.2. Creating a ContainerRuntimeConfig CR to edit CRI-O parameters
Copiar enlace

3.3.3. Setting the default maximum container root partition size for Overlay with CRI-O
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