[cka] Static PODs

Static PODs 란?

 

https://kubernetes.io/docs/tasks/configure-pod-container/static-pod/

Create static Pods

 

static pod의 동작 원리
- API를 통하지 않고 파드가 생성된다.
- 각 노드의 kubelet에게 static pod 생성 요청
- /var/lib/kubelet/config.yaml -> kubelet 구성 정보, static 파드를 동작시킬 위치 정보가 등록되어 있음
- 기본값은 /etc/kubernetes/manifest로 되어있다.
- /etc/kubernetes/manifest 에 pod.yaml를 등록해주면 kubelet이 해당 yaml 파일을 기준으로 파드를 생성한다.
- master 의 API, Scheduler, ETCD, Controller 도 전부 static pod 형태로 동작한다.

 

1. How many static pods exist in this cluster in all namespaces?

$ controlplane ~ ➜  k get pod -A
NAMESPACE      NAME                                   READY   STATUS    RESTARTS   AGE
kube-flannel   kube-flannel-ds-nrzlc                  1/1     Running   0          11m
kube-flannel   kube-flannel-ds-shwvw                  1/1     Running   0          11m
kube-system    coredns-768b85b76f-898jj               1/1     Running   0          11m
kube-system    coredns-768b85b76f-gpwfz               1/1     Running   0          11m
kube-system    etcd-controlplane                      1/1     Running   0          11m
kube-system    kube-apiserver-controlplane            1/1     Running   0          11m
kube-system    kube-controller-manager-controlplane   1/1     Running   0          11m
kube-system    kube-proxy-qr6qk                       1/1     Running   0          11m
kube-system    kube-proxy-wf8r8                       1/1     Running   0          11m
kube-system    kube-scheduler-controlplane            1/1     Running   0          11m

 

answer : 4

kube-system 에 controlplane 으로 실행중인 POD 들이 static POD 형태로 실행중이다.

 

2. Which of the below components is NOT deployed as a static pod?

 

answer :  coredns

-> controlplane suffix 가 없다.

 

3. Which of the below components is NOT deployed as a static POD?

answer : kube-proxy

2번과 동일한 이유.

 

4. On which nodes are the static pods created currently?

 

answer : controlplane

 

 

5. What is the path of the directory holding the static pod definition files?

$ controlplane ~ ➜  ls /etc/kubernetes/manifests/
etcd.yaml  kube-apiserver.yaml  kube-controller-manager.yaml  kube-scheduler.yaml

answer : /etc/kubernetes/manifests/

6.  How many pod definition files are present in the manifests directory?

answer : 4

7.  What is the docker image used to deploy the kube-api server as a static pod?

 

$ controlplane ~ ➜  k describe pod kube-apiserver-controlplane -n kube-system
...

Events:
  Type    Reason   Age   From     Message
  ----    ------   ----  ----     -------
  Normal  Pulled   22m   kubelet  Container image "registry.k8s.io/kube-apiserver:v1.30.0" already present on machine
  Normal  Created  22m   kubelet  Created container kube-apiserver
  Normal  Started  22m   kubelet  Started container kube-apiserver

 

answer : registry.k8s.io/kube-apiserver:v1.30.0

 

 

8. Create a static pod named static-busybox that uses the busybox image and the command sleep 1000

 

$ controlplane ~ ✖ kubectl run --restart=Never --image=busybox static-busybox --dry-run=client -o yaml --command -- sleep 1000 > static-busybox.yaml

$ controlplane ~ ➜  mv static-busybox.yaml /etc/kubernetes/manifests/

$ controlplane ~ ➜  k get pods -A
NAMESPACE      NAME                                   READY   STATUS    RESTARTS   AGE
default        static-busybox-controlplane            1/1     Running   0          5s
kube-flannel   kube-flannel-ds-nrzlc                  1/1     Running   0          25m
kube-flannel   kube-flannel-ds-shwvw                  1/1     Running   0          25m
kube-system    coredns-768b85b76f-898jj               1/1     Running   0          25m
kube-system    coredns-768b85b76f-gpwfz               1/1     Running   0          25m
kube-system    etcd-controlplane                      1/1     Running   0          26m
kube-system    kube-apiserver-controlplane            1/1     Running   0          26m
kube-system    kube-controller-manager-controlplane   1/1     Running   0          26m
kube-system    kube-proxy-qr6qk                       1/1     Running   0          25m
kube-system    kube-proxy-wf8r8                       1/1     Running   0          25m
kube-system    kube-scheduler-controlplane            1/1     Running   0          26m

 

 

9.  Edit the image on the static pod to use busybox:1.28.4

 

$ controlplane ~ ➜  rm /etc/kubernetes/manifests/static-busybox.yaml 

$ controlplane ~ ✖ kubectl run --restart=Never --image=busybox:1.28.4 static-busybox --dry-run=client -o yaml --command -- sleep 1000 > /etc/kubernetes/manifests/static-busybox.yaml

$ controlplane ~ ➜  k get pods
NAME                          READY   STATUS    RESTARTS   AGE
static-busybox-controlplane   1/1     Running   0          2s

 

10.  We just created a new static pod named static-greenbox. Find it and delete it.

 

This question is a bit tricky. But if you use the knowledge you gained in the previous questions in this lab, you should be able to find the answer to it.

 

$ controlplane ~ ➜  k get pods
NAME                          READY   STATUS    RESTARTS   AGE
static-busybox-controlplane   1/1     Running   0          6m44s
static-greenbox-node01        1/1     Running   0          5m10s

 

10-1. static-greenbox 가 suffix가 node01 로 끝나므로 node01 노드에서 생성한 static-pod 라는것을 알수 있었다.

ssh를 이용하여 node01 로 접속해본다.

$ controlplane ~ ➜  ssh node01
Last login: Sun Jun 23 13:15:35 2024 from 192.20.241.10

 

10-2. 해당 노드로 접속한후 static pod 위치를 확인해본다.

static pod 정보는 kubelet 의 config 정보에 존재한다.

 

$ node01 ~ ➜  ps -ef | grep kubelet
root       12920       1  0 13:13 ?        00:00:08 /usr/bin/kubelet --bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kubernetes/kubelet.conf --config=/var/lib/kubelet/config.yaml --container-runtime-endpoint=unix:///var/run/containerd/containerd.sock --pod-infra-container-image=registry.k8s.io/pause:3.9


$ node01 ~ ➜  cat /var/lib/kubelet/config.yaml | grep  static
staticPodPath: /etc/just-to-mess-with-you

 

 

10-3. 해당 경로에 있는 greenbox.yaml 을 삭제한후 static-pod 가 종료되길 기다린다.

 

$ node01 /etc ➜  rm ./just-to-mess-with-you/greenbox.yaml