[cka] Manual Scheduling

 

1. A pod definition file nginx.yaml is given. Create a pod using the file.

Only create the POD for now. We will inspect its status next.

 

$ controlplane ~ ➜  k apply -f nginx.yaml 
pod/nginx created

 

 

2.  What is the status of the created POD?

$ controlplane ~ ➜  k get pods
NAME    READY   STATUS    RESTARTS   AGE
nginx   0/1     Pending   0          31s

 

answer : Pending

 

3. Why is the POD in a pending state?
Inspect the environment for various kubernetes control plane components.

$ controlplane ~ ➜  k get pods -n kube-system
NAME                                   READY   STATUS    RESTARTS   AGE
coredns-69f9c977-hj2nb                 1/1     Running   0          6m24s
coredns-69f9c977-xj8c9                 1/1     Running   0          6m23s
etcd-controlplane                      1/1     Running   0          6m35s
kube-apiserver-controlplane            1/1     Running   0          6m42s
kube-controller-manager-controlplane   1/1     Running   0          6m35s
kube-proxy-29dhc                       1/1     Running   0          6m24s
kube-proxy-phjtj                       1/1     Running   0          5m59s

동작중인 kube-scheduler 가없다. 보통은 kube-scheduler를 통해 노드를 자동으로 배정해 주지만 현재 실습 환경에서는 scheduler가없기 때문에 node 를 직접 명시해 주어 pod를 실행시켜야 한다.

 

https://kubernetes.io/docs/reference/command-line-tools-reference/kube-scheduler/

kube-scheduler

 

Synopsis

The Kubernetes scheduler is a control plane process which assigns Pods to Nodes. 

 

kube-scheduler 가 없으면 pods 를 실행해도 노드에 배치해 줄수 없다.

 

answer : No Scheduler Present

 

 

4. Manually schedule the pod on node01.
Delete and recreate the POD if necessary.

$ controlplane ~ ➜  k delete po nginx 
pod "nginx" deleted

## in nginx.yaml

apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  nodeName: node01
  containers:
  -  image: nginx
     name: nginx
     
-------

$ controlplane ~ ➜  k apply -f nginx.yaml 
pod/nginx created

 

 

5. Now schedule the same pod on the controlplane node.
Delete and recreate the POD if necessary.

 

$ controlplane ~ ➜  k delete po nginx 
pod "nginx" deleted

## in nginx.yaml

apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  nodeName: controlplane
  containers:
  -  image: nginx
     name: nginx
     
-------

$ controlplane ~ ➜  k apply -f nginx.yaml 
pod/nginx created