Node Drain and Cordon#
Node maintenance is a routine part of cluster operations: kernel patches, instance type changes, Kubernetes upgrades, hardware replacement. The tools are kubectl cordon (stop scheduling new pods) and kubectl drain (evict existing pods). Getting the flags and sequence right is the difference between a seamless operation and a production incident.
Cordon: Mark Unschedulable#
Cordon sets the spec.unschedulable field on a node to true. The scheduler will not place new pods on it, but existing pods continue running undisturbed.