Boîte à outil K8S – devopsopen

get all resources in a cluster

kubectl get all -A

Sort cpu or memory of pods or nodes(Find the pod who consumm more than others)

install server metrics

wget  https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml

add those line into file yaml

        command:
          - /metrics-server
          - --kubelet-insecure-tls
          - --kubelet-preferred-address-types=InternalIP

spec:
  selector:
    matchLabels:
      k8s-app: metrics-server
  strategy:
    rollingUpdate:
      maxUnavailable: 0
  template:
    metadata:
      labels:
        k8s-app: metrics-server
    spec:
      containers:
      - args:
        - --cert-dir=/tmp
        - --secure-port=4443
        - --kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname
        - --kubelet-use-node-status-port
        - --metric-resolution=15s
        image: registry.k8s.io/metrics-server/metrics-server:v0.6.4
        command:
          - /metrics-server
          - --kubelet-insecure-tls
          - --kubelet-preferred-address-types=InternalIP
        imagePullPolicy: IfNotPresent
        livenessProbe:
          failureThreshold: 3
          httpGet:

then apply the file

kubectl apply -f components.yaml

then get sorted informations

kubectl top pod | awk '{ print $1 ";" $2 ";" $3}' > sort.in ; sort -t";" -V -k3 sort.in

-t is seprator
-V alphanumeric
-k3 column 3 to be sorted
sort.in the file input

Info cluster service CIDR...

kubectl cluster-info dump | grep -i service-cluster
kubectl cluster-info dump | grep -i cluster-cidr

Change image of a deployment

create a deployment with image

kubectl create deploy nginx-deploy --image=nginx:1.16 --replicas=1

change the image of the deployment

kubectl set image deployment nginx-deploy nginx=nginx:1.17

get all pod in a specific node

kubectl get pods --all-namespaces -o wide --field-selector spec.nodeName=<node>

Migrate pods where are in a specific node to another node

unschedule pods with cordon command to not let other pods to come to this node.
kubectl cordon node-1

drain node(vider) to exclude pods to other pods that are scheduled. drain containt the cordon command naturally
kubectl drain node-2 --force

get node scheduled with command uncordon
kubectl uncordon node-1

Make a node unavailable

kubectl drain node-01 --force  
or
kubectl drain node-01 --grace-period 0

Creation pod:

kubectl run static-busybox --image=busybox --command "sleep 1000" --dry-run=client -o yaml

Création deploy

kubectl create deployment hr-web-app --image=redis --replicas=3 --dry-run=client -o yaml

Scale a Deploy or RS

kubectl scale deploy/test2 --replicas=3

Expose a pod (deploy or rs)

kubectl expose pod messaging --name=messaging-service --type=ClusterIP --port=6379

Create a static pod (important because static pod does not scheduled by api, you should put it in manifests)

kubectl run --restart=Never --image=busybox static-busybox --dry-run=client -o yaml --command -- sleep 1000 > /etc/kubernetes/manifests/static-busybox.yaml

Create deploy with replicas

kubectl create deployment hr-web-app --image=kodekloud/webapp-color --replicas=2

Correct a pod description with edit command. when you edit a pod, a temp file is created and you should force

kubectl edit pod namepod
kubectl replace -f /tmp/kubectl-edit-xxxx.yaml --force

Expose a deploy with a specific NodePort. after this command you should change the port wanted in the file

kubectl expose deployment hr-web-app --type=NodePort --port=8080 --name=hr-web-app-service --dry-run=client -o yaml > hr-web-app-service.yaml

Get OSImage of nodes and put in the file

kubectl get nodes -o jsonpath='{.items[*].status.nodeInfo.osImage}' > /opt/outputs/nodes_os_x43kj56.txt

Create a persistent volume

apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-analytics
spec:
  capacity:
    storage: 100Mi
  volumeMode: Filesystem
  accessModes:
    - ReadWriteMany
  hostPath:
      path: /pv/data-analytics

Lens pour gérer son Cluster

Télécharger et installer Lens Open : Lien
Récupérer la conf de votre cluster depuis Kub avec la commande :

kubectl config view --minify --raw
Or
kubectl config view --flatten > out.txt

Ajouter la conf dans la fenêtre ci-dessous

Use JsonPath to extract informations with kubectl

https://kubernetes.io/docs/reference/kubectl/jsonpath/

The list bellow can help you, but for more details please see the link above

kubectl config view 

Result :

clusters:
- cluster:
    certificate-authority-data: DATA+OMITTED
    server: https://111.97.79.11:6443
  name: kubernetes
contexts:
- context:
    cluster: kubernetes
    namespace: ns-0001-example-prod
    user: kubernetes-admin
  name: kubernetes-admin@kubernetes
current-context: kubernetes-admin@kubernetes
kind: Config
preferences: {}
users:
- name: kubernetes-admin
  user:
    client-certificate-data: DATA+OMITTED
    client-key-data: DATA+OMITTED

kubectl config view -o jsonpath='{..namespace}'
result : ns-0001-example-prod