Priority Class

Always first look for already available priority classes before creating newer one
To set priority in pod template, priority class needs to create first.

Create new Pod named important of image nginx:1.21.6-alpine in the same Namespace. It should request 1Gi memory resources.

Assign a higher priority to the new Pod so it's scheduled instead of the existing one.

controlplane:~$ vi 2.yaml 
controlplane:~$ k replace -f 2.yaml --force
pod "important" deleted
pod/important replaced

controlplane:~$ k get po -n lion
NAME        READY   STATUS        RESTARTS   AGE
4d37006c    0/1     OutOfmemory   0          3m8s        # priorityClassName: level2
important   1/1     Running       0          5s

controlplane:~$ cat 2.yaml 
apiVersion: v1
kind: Pod
metadata:
  labels:
    run: important
  name: important
  namespace: lion
spec:
  priorityClassName: level3          # Note: don't create a new pc, it's been provided already.
  containers:
  - image: nginx:1.21.6-alpine
    name: important
    resources:
      requests:
        memory: 1Gi
  dnsPolicy: ClusterFirst
  restartPolicy: Always
controlplane:~$ k get pc
NAME                      VALUE        GLOBAL-DEFAULT   AGE     PREEMPTIONPOLICY
level2                    200000000    false            19m     PreemptLowerPriority
level3                    300000000    false            19m     PreemptLowerPriority
system-cluster-critical   2000000000   false            2d19h   PreemptLowerPriority
system-node-critical      2000001000   false            2d19h   PreemptLowerPriority
controlplane:~$