If you are not familiar with the oc command, refer to OpenShift - Getting Started with the oc command.

I like to think of a "machine" as OpenShift representation of a Virtual Machine, such as an Amazon Web Services (AWS) EC2 Instance, or a VMWare Virtual Machine, and then a Node, and then the pods running on the node.

The oc get nodes command will return the list of nodes, something like this.

~]# oc get nodes
NAME              STATUS   ROLES            AGE    VERSION
my-edge-lm6wz     Ready    infra,worker     667d   v1.24.12+8f6c8a6
my-edge-pmlls     Ready    infra,worker     667d   v1.24.12+8f6c8a6
my-infra-c4v5h    Ready    infra,worker     667d   v1.24.12+8f6c8a6
my-infra-mc8rc    Ready    infra,worker     667d   v1.24.12+8f6c8a6
my-infra-p9cjv    Ready    infra,worker     667d   v1.24.12+8f6c8a6
my-master-0       Ready    master           670d   v1.24.12+8f6c8a6
my-master-1       Ready    master           670d   v1.24.12+8f6c8a6
my-master-2       Ready    master           670d   v1.24.12+8f6c8a6
my-worker-lk5vm   Ready    compute,worker   209d   v1.24.12+8f6c8a6
my-worker-pj4r4   Ready    compute,worker   209d   v1.24.12+8f6c8a6

The oc debug command can be used to start a node in debug mode.

oc debug node/my-node-5n4fj

If something like "Pod Predicate NodeAffinity failed" is returned . . .

error: debug pod could not be scheduled: Pod Predicate NodeAffinity failed. To fix this you may want to create a new namespace with empty node selector and run the debug there. For example: oc adm new-project --node-selector="" debug

. . . you can do as the error output suggests and use the oc adm new-project command to create a "debug" project with an empty node selector annotation.

oc adm new-project --node-selector="" debug

And then use the oc project command to switch over to the "debug" project.

oc project debug

The oc debug command can be used to start a node in debug mode. This will provide you with a command line prompt in a "debug" pod for the node that can be used for debugging purposes.

~]# oc debug node/my-node-5n4fj
Starting pod/my-node-5n4fj-debug ...
sh-4.4#

Typically you will first issue the chroot /host command is used to set /host as the root directory because the root file system is mounted to /host in the debug pod.

sh-4.4# chroot /host

And then you can use the systemctl reboot command to reboot the node.

sh-4.4# systemctl reboot

Or, better yet, this one liner command can be used.

oc debug node/<node name> -- chroot /host systemctl reboot