title: “Certification Details”
date: 2019-07-12T08:44:38
slug: certification-details
https://www.youtube.com/watch?v=DFEOdnYw1WY
https://www.youtube.com/watch?v=Y2SA7sCtKSs
Certified Kubernetes Administrator: https://www.cncf.io/certification/cka/
Exam Curriculum (Topics): https://github.com/cncf/curriculum
Candidate Handbook: https://www.cncf.io/certification/candidate-handbook
Exam Tips: http://training.linuxfoundation.org/go//Important-Tips-CKA-CKAD
Kubernetes Tab Completion
source <(kubectl completion bash)
echo "source <(kubectl completion bash)" >> ~/.bashrc
Create a nginx Deployment
kubectl run nginx --image=nginx
Create deployment with X replicas
!!TODO
Create a pod with name and image
kubectl run redis --image=redis123 --generator=run-pod/v1.
Generate Pod Manifest
kubectl run --generator=run-pod/v1 nginx --image=nginx --dry-run -o yaml
Create Pod with command line args:
kubectl run webapp --image=webapp --generator=run-pod/v1 --dry-run -o yaml -- --color=green
Extended information
kubectl get pods -o wide
Edit a Pod
kubectl edit pod nginx
Delete all pods
kubectl delete --all pods --namespace=foo
Create a Service (ClusterIP)
kubectl expose pod redis --port=6379 --name redis-service --dry-run -o yaml
Expose Pod:
kubectl expose pod nginx --port=80 --name nginx-service --dry-run -o yaml
Create Service Nodeport (not using selector, you have to correct it in yaml)
kubectl create service nodeport nginx --tcp=80:80 --node-port=30080 --dry-run -o yaml
Übung:
Name: webapp-service
Type: NodePort
Endpoints: 3
Port: 8080
NodePort: 30082
kubectl expose deployment webapp --type=NodePort --port=8080 --name=webapp-service
And edit the nodeport with kubectl edit or create manifest first
Assign Pod to a node by nodeName
apiVersion: v1
kind: Pod
metadata:
name: nginx
spec:
nodeName: foo-node # schedule pod to specific node
containers:
- name: nginx
Get pods by selector
kubectl get pods --selector env=dev
kubectl get pods --selector env=dev,bu=finance,tier=frontend
Pod Manifest:
labels:
env: dev
You CANNOT edit specifications of an existing POD other than the below.
spec.containers[\*].image
spec.initContainers[\*].image
spec.activeDeadlineSeconds
spec.tolerations
Edit Deployments
With Deployments you can easily edit any field/property of the POD template. Since the pod template is a child of the deployment specification, with every change the deployment will automatically delete and create a new pod with the new changes. So if you are asked to edit a property of a POD part of a deployment you may do that simply by running the command
kubectl edit deployment my-deployment
Create Custom Scheduler
apiVersion: v1
kind: Pod
metadata:
name: my-scheduler
namespace: kube-system
spec:
containers:
- command:
- kube-scheduler
- --address=127.0.0.1
- --kubeconfig=/etc/kubernetes/scheduler.conf
- --leader-elect=false
- --scheduler-name=my-scheduler
image: gcr.io/my-gcp-project/my-kube-scheduler:1.0
Assign Pod to scheduler
apiVersion: v1
kind: Pod
metadata:
name: annotation-default-scheduler
labels:
name: multischeduler-example
spec:
schedulerName: my-scheduler
containers:
- name: pod-with-default-annotation-container
image: k8s.gcr.io/pause:2.0
Create a configmap
kubectl create configmap special-config --from-literal=special.how=very --from-literal=special.type=charm
Assign the configmap to a pod:
apiVersion: v1
kind: Pod
metadata:
name: dapi-test-pod
spec:
containers:
- name: test-container
image: k8s.gcr.io/busybox
command: [ "/bin/sh", "-c", "env" ]
env:
# Define the environment variable
- name: SPECIAL\_LEVEL\_KEY
valueFrom:
configMapKeyRef:
# The ConfigMap containing the value you want to assign to SPECIAL\_LEVEL\_KEY
name: special-config
# Specify the key associated with the value
key: special.how
restartPolicy: Never
Create a secret with multiple vars
kubectl create secret generic test-secret --from-literal=username='my-app' --from-literal=password='39528$vdg7Jb'
Pass it to aPod as environmend
apiVersion: v1
kind: Pod
metadata:
name: envfrom-secret
spec:
containers:
- name: envars-test-container
image: nginx
envFrom:
- secretRef:
name: test-secret
Create a pod with two init container
apiVersion: v1
kind: Pod
metadata:
name: myapp-pod
labels:
app: myapp
spec:
containers:
- name: myapp-container
image: busybox:1.28
command: ['sh', '-c', 'echo The app is running! && sleep 3600']
initContainers:
- name: init-myservice
image: busybox:1.28
command: ['sh', '-c', 'until nslookup myservice; do echo waiting for myservice; sleep 2; done;']
- name: init-mydb
image: busybox:1.28
command: ['sh', '-c', 'until nslookup mydb; do echo waiting for mydb; sleep 2; done;']
Pod dead timeout
--pod-eviction-timeout duration Default: 5m0s
Upgrade the Master Node (drain first)
apt install kubeadm=1.12.10-00
kubeadm update apply v1.12.10
Update the worker node (drain first)
apt install kubeadm=1.12.0-00
apt install kubelet=1.12.0-00
kubeadm upgrade node config --kubelet-version $(kubelet --version | cut -d ' ' -f 2)
Cluster backup 1
kubectl get all --all-namespaces -o yaml > all-deploy-services.yaml
Check multiple certificates
ls \*crt | xargs -n 1 sh -c 'openssl x509 -in $0 -text -noout' | grep -i after