Beginning with OpenShift v4.18, the default container runtime became crun.

https://docs.redhat.com/ja/documentation/openshift_container_platform/4.18/html/release_notes/ocp-4-18-new-features-and-enhancements_release-notes#ocp-release-notes-nodes-crun-default_release-notes

This change is synchronized with CRI-O v1.31, which also changed its default runtime to crun.

https://github.com/cri-o/cri-o/releases/tag/v1.31.0

Therefore, for v4.18 and later (including 4.19 and 4.20), changes must be made at the following location (in the document):

crun has several improvements over runC, including:
Smaller binary
Quicker processing
Lower memory footprint
Default container runtime of CRI-O

https://docs.redhat.com/en/documentation/openshift_container_platform/4.18/html/nodes/working-with-containers#nodes-containers-runtimes
https://docs.redhat.com/en/documentation/openshift_container_platform/4.19/html/nodes/working-with-containers#nodes-containers-runtimes
https://docs.redhat.com/en/documentation/openshift_container_platform/4.20/html/nodes/working-with-containers#nodes-containers-runtimes

4.18, 4.19, 4.20    

    1.
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    3.
    

This is feedback received from our Japanese Senior Specialist Solution Architect.