[cka] DaemonSets

DaemonSet ?

 

https://kubernetes.io/docs/concepts/workloads/controllers/daemonset/

DaemonSet

 

각 노드마다 필수적으로 실행되는 Pod, 노드가 생성될때 생성되고 노드가 삭제되면 삭제되는 Pod 이다.

 

1. How many DaemonSets are created in the cluster in all namespaces?
Check all namespaces

 

controlplane ~ ➜  k get daemonsets.apps -A
NAMESPACE      NAME              DESIRED   CURRENT   READY   UP-TO-DATE   AVAILABLE   NODE SELECTOR            AGE
kube-flannel   kube-flannel-ds   1         1         1       1            1           <none>                   5m24s
kube-system    kube-proxy        1         1         1       1            1           kubernetes.io/os=linux   5m25s

 

answer : 2

 

2. Which namespace is the kube-proxy Daemonset created in?

kubectl get all --all-namespaces 
NAMESPACE      NAME                                       READY   STATUS    RESTARTS   AGE
kube-flannel   pod/kube-flannel-ds-pttqs                  1/1     Running   0          24m
kube-system    pod/coredns-768b85b76f-8btn4               1/1     Running   0          24m
kube-system    pod/coredns-768b85b76f-dzkxh               1/1     Running   0          24m
kube-system    pod/etcd-controlplane                      1/1     Running   0          25m
kube-system    pod/kube-apiserver-controlplane            1/1     Running   0          25m
kube-system    pod/kube-controller-manager-controlplane   1/1     Running   0          25m
kube-system    pod/kube-proxy-qvnp7                       1/1     Running   0          24m
kube-system    pod/kube-scheduler-controlplane            1/1     Running   0          25m

NAMESPACE     NAME                 TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)                  AGE
default       service/kubernetes   ClusterIP   10.96.0.1    <none>        443/TCP                  25m
kube-system   service/kube-dns     ClusterIP   10.96.0.10   <none>        53/UDP,53/TCP,9153/TCP   25m

NAMESPACE      NAME                             DESIRED   CURRENT   READY   UP-TO-DATE   AVAILABLE   NODE SELECTOR            AGE
kube-flannel   daemonset.apps/kube-flannel-ds   1         1         1       1            1           <none>                   25m
kube-system    daemonset.apps/kube-proxy        1         1         1       1            1           kubernetes.io/os=linux   25m

NAMESPACE     NAME                      READY   UP-TO-DATE   AVAILABLE   AGE
kube-system   deployment.apps/coredns   2/2     2            2           25m

NAMESPACE     NAME                                 DESIRED   CURRENT   READY   AGE
kube-system   replicaset.apps/coredns-768b85b76f   2         2         2       24m

answer : kube-flannel-ds

 

4. On how many nodes are the pods scheduled by the DaemonSet kube-proxy?

controlplane ~ ➜  k get daemonsets.apps -A
NAMESPACE      NAME              DESIRED   CURRENT   READY   UP-TO-DATE   AVAILABLE   NODE SELECTOR            AGE
kube-flannel   kube-flannel-ds   1         1         1       1            1           <none>                   39m
kube-system    kube-proxy        1         1         1       1            1           kubernetes.io/os=linux   39m

 

answer : 1

 

 

5. What is the image used by the POD deployed by the kube-flannel-ds DaemonSet?

 

controlplane ~ ➜  k get daemonsets.apps -A -o wide
NAMESPACE      NAME              DESIRED   CURRENT   READY   UP-TO-DATE   AVAILABLE   NODE SELECTOR            AGE   CONTAINERS     IMAGES                               SELECTOR
kube-flannel   kube-flannel-ds   1         1         1       1            1           <none>                   16m   kube-flannel   docker.io/flannel/flannel:v0.23.0    app=flannel,k8s-app=flannel
kube-system    kube-proxy        1         1         1       1            1           kubernetes.io/os=linux   16m   kube-proxy     registry.k8s.io/kube-proxy:v1.30.0   k8s-app=kube-proxy

 

answer : docker.io/flannel/flannel:v0.23.0

 

6. Deploy a DaemonSet for FluentD Logging. Use the given specifications.

 

controlplane ~ ➜  kubectl create deployment elasticsearch --image=registry.k8s.io/fluentd-elasticsearch:1.20 -n kube-system --dry-run=client -o yaml > fluentd.yaml


### fluentd.yaml

apiVersion: apps/v1
kind: DaemonSet # Deployment -> DaemonSet 변경
metadata:
  creationTimestamp: null
  labels:
    app: elasticsearch
  name: elasticsearch
  namespace: kube-system
spec:
#  replicas: 1 # 제거
  selector:
    matchLabels:
      app: elasticsearch
#  strategy: {} 제거
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: elasticsearch
    spec:
      containers:
      - image: registry.k8s.io/fluentd-elasticsearch:1.20
        name: fluentd-elasticsearch
        resources: {}
status: {}

## 

controlplane ~ ➜  k apply -f fluentd.yaml 
daemonset.apps/elasticsearch created