There are times when you need to make changes to the operating systems running on {product-title} 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 {product-title} 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 {product-title} 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 {product-title} 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 {product-title}.
{product-title} 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 {product-title} cluster, any existing Ignition specification version 2.x machine configs will be translated automatically to specification version 3.2.
There might be situations where the configuration on a node does not fully match what the currently-applied machine config specifies. This state is called configuration drift. The Machine Config Daemon (MCD) regularly checks the nodes for configuration drift. If the MCD detects configuration drift, the MCO marks the node degraded until an administrator corrects the node configuration. A degraded node is online and operational, but, it cannot be updated. For more information on configuration drift, see Understanding configuration drift detection.
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Tip
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Use the following "Configuring chrony time service" procedure as a model for how to go about adding other configuration files to {product-title} nodes. |
modules/cnf-disable-chronyd.adoc modules/nodes-nodes-kernel-arguments.adoc modules/rhcos-enabling-multipath-day-2.adoc
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See Enabling multipathing with kernel arguments on RHCOS for more information about enabling multipathing during installation time.
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.