til/docs/server/kubernetes.md

• https://kubernetes.io/

• https://kubernetes.io/docs/home/

  ### notes ###
  

---

sheet source - https://github.com/dennyzhang/cheatsheet-kubernetes-A4

Common Commands

Name	Command
Run curl test temporarily	kubectl run --rm mytest --image=yauritux/busybox-curl -it
Run wget test temporarily	kubectl run --rm mytest --image=busybox -it
Run nginx deployment with 2 replicas	kubectl run my-nginx --image=nginx --replicas=2 --port=80
Run nginx pod and expose it	kubectl run my-nginx --restart=Never --image=nginx --port=80 --expose
Run nginx deployment and expose it	kubectl run my-nginx --image=nginx --port=80 --expose
Set namespace preference	kubectl config set-context <context_name> --namespace=<ns_name>
List pods with nodes info	kubectl get pod -o wide
List everything	kubectl get all --all-namespaces
Get all services	kubectl get service --all-namespaces
Get all deployments	kubectl get deployments --all-namespaces
Show nodes with labels	kubectl get nodes --show-labels
Get resources with json output	kubectl get pods --all-namespaces -o json
Validate yaml file with dry run	kubectl create --dry-run --validate -f pod-dummy.yaml
Start a temporary pod for testing	kubectl run --rm -i -t --image=alpine test-$RANDOM -- sh
kubectl run shell command	kubectl exec -it mytest -- ls -l /etc/hosts
Get system conf via configmap	kubectl -n kube-system get cm kubeadm-config -o yaml
Get deployment yaml	kubectl -n denny-websites get deployment mysql -o yaml
Explain resource	kubectl explain pods, kubectl explain svc
Watch pods	kubectl get pods -n wordpress --watch
Query healthcheck endpoint	curl -L http://127.0.0.1:10250/healthz
Open a bash terminal in a pod	kubectl exec -it storage sh
Check pod environment variables	kubectl exec redis-master-ft9ex env
Enable kubectl shell autocompletion	echo "source <(kubectl completion bash)" >>~/.bashrc, and reload
Use minikube dockerd in your laptop	eval $(minikube docker-env), No need to push docker hub any more
Kubectl apply a folder of yaml files	kubectl apply -R -f .
Get services sorted by name	kubectl get services –sort-by=.metadata.name
Get pods sorted by restart count	kubectl get pods –sort-by='.status.containerStatuses[0].restartCount'
List pods and images	kubectl get pods -o='custom-columns=PODS:.metadata.name,Images:.spec.containers[*].image'
List all container images	list-all-images.sh
kubeconfig skip tls verification	skip-tls-verify.md
Ubuntu install kubectl	"deb https://apt.kubernetes.io/ kubernetes-xenial main"
Reference	GitHub: kubernetes releases
Reference	minikube cheatsheet, docker cheatsheet, OpenShift CheatSheet

Check Performance

Name	Command
Get node resource usage	kubectl top node
Get pod resource usage	kubectl top pod
Get resource usage for a given pod	kubectl top <podname> --containers
List resource utilization for all containers	kubectl top pod --all-namespaces --containers=true

Resources Deletion

Name	Command
Delete pod	kubectl delete pod/<pod-name> -n <my-namespace>
Delete pod by force	kubectl delete pod/<pod-name> --grace-period=0 --force
Delete pods by labels	kubectl delete pod -l env=test
Delete deployments by labels	kubectl delete deployment -l app=wordpress
Delete all resources filtered by labels	kubectl delete pods,services -l name=myLabel
Delete resources under a namespace	kubectl -n my-ns delete po,svc --all
Delete persist volumes by labels	kubectl delete pvc -l app=wordpress
Delete state fulset only (not pods)	kubectl delete sts/<stateful_set_name> --cascade=false

Log & Conf Files

Name	Comment
Config folder	/etc/kubernetes/
Certificate files	/etc/kubernetes/pki/
Credentials to API server	/etc/kubernetes/kubelet.conf
Superuser credentials	/etc/kubernetes/admin.conf
kubectl config file	~/.kube/config
Kubernets working dir	/var/lib/kubelet/
Docker working dir	/var/lib/docker/, /var/log/containers/
Etcd working dir	/var/lib/etcd/
Network cni	/etc/cni/net.d/
Log files	/var/log/pods/
log in worker node	/var/log/kubelet.log, /var/log/kube-proxy.log
log in master node	kube-apiserver.log, kube-scheduler.log, kube-controller-manager.log
Env	/etc/systemd/system/kubelet.service.d/10-kubeadm.conf
Env	export KUBECONFIG=/etc/kubernetes/admin.conf

Pod

Name	Command
List all pods	kubectl get pods
List pods for all namespace	kubectl get pods -all-namespaces
List all critical pods	kubectl get -n kube-system pods -a
List pods with more info	kubectl get pod -o wide, kubectl get pod/<pod-name> -o yaml
Get pod info	kubectl describe pod/srv-mysql-server
List all pods with labels	kubectl get pods --show-labels
List all unhealthy pods	kubectl get pods –field-selector=status.phase!=Running –all-namespaces
List running pods	kubectl get pods –field-selector=status.phase=Running
kubectl run command	kubectl exec -it -n "$ns" "$podname" – sh -c "echo $msg >>/dev/err.log"
Watch pods	kubectl get pods -n wordpress --watch
Get pod by selector	kubectl get pods –selector="app=syslog" -o jsonpath='{.items[*].metadata.name}'
List pods and images	kubectl get pods -o='custom-columns=PODS:.metadata.name,Images:.spec.containers[*].image'
List pods and containers	-o='custom-columns=PODS:.metadata.name,CONTAINERS:.spec.containers[*].name'
Reference	Link: kubernetes yaml templates

Label & Annontation

Name	Command
Filter pods by label	kubectl get pods -l owner=denny
Manually add label to a pod	kubectl label pods dummy-input owner=denny
Remove label	kubectl label pods dummy-input owner-
Manually add annonation to a pod	kubectl annotate pods dummy-input my-url=https://dennyzhang.com

Deployment & Scale

Name	Command
Scale out	kubectl scale --replicas=3 deployment/nginx-app
online rolling upgrade	kubectl rollout app-v1 app-v2 --image=img:v2
Roll backup	kubectl rollout app-v1 app-v2 --rollback
List rollout	kubectl get rs
Check update status	kubectl rollout status deployment/nginx-app
Check update history	kubectl rollout history deployment/nginx-app
Pause/Resume	kubectl rollout pause deployment/nginx-deployment, resume
Rollback to previous version	kubectl rollout undo deployment/nginx-deployment
Reference	Link: kubernetes yaml templates, Link: Pausing and Resuming a Deployment

Quota & Limits & Resource

Name	Command
List Resource Quota	kubectl get resourcequota
List Limit Range	kubectl get limitrange
Customize resource definition	kubectl set resources deployment nginx -c=nginx --limits=cpu=200m
Customize resource definition	kubectl set resources deployment nginx -c=nginx --limits=memory=512Mi
Reference	Link: kubernetes yaml templates

Service

Name	Command
List all services	kubectl get services
List service endpoints	kubectl get endpoints
Get service detail	kubectl get service nginx-service -o yaml
Expose deployment as lb service	kubectl expose deployment/my-app --type=LoadBalancer --name=my-service
Expose service as lb service	kubectl expose service/wordpress-1-svc --type=LoadBalancer --name=ns1
Reference	Link: kubernetes yaml templates

Secrets

Name	Command
List secrets	kubectl get secrets --all-namespaces
Generate secret	echo -n 'mypasswd', then redirect to base64 --decode
Get secret	kubectl get secret denny-cluster-kubeconfig
Get a specific field of a secret	kubectl get secret denny-cluster-kubeconfig -o jsonpath="{.data.value}"
Create secret from cfg file	kubectl create secret generic db-user-pass –from-file=./username.txt
Reference	Link: kubernetes yaml templates, Link: Secrets

StatefulSet

Name	Command
List statefulset	kubectl get sts
Delete statefulset only (not pods)	kubectl delete sts/<stateful_set_name> --cascade=false
Scale statefulset	kubectl scale sts/<stateful_set_name> --replicas=5
Reference	Link: kubernetes yaml templates

Volumes & Volume Claims

Name	Command
List storage class	kubectl get storageclass
Check the mounted volumes	kubectl exec storage ls /data
Check persist volume	kubectl describe pv/pv0001
Copy local file to pod	kubectl cp /tmp/my <some-namespace>/<some-pod>:/tmp/server
Copy pod file to local	kubectl cp <some-namespace>/<some-pod>:/tmp/server /tmp/my
Reference	Link: kubernetes yaml templates

Events & Metrics

Name	Command
View all events	kubectl get events --all-namespaces
List Events sorted by timestamp	kubectl get events –sort-by=.metadata.creationTimestamp

Node Maintenance

Name	Command
Mark node as unschedulable	kubectl cordon $NDOE_NAME
Mark node as schedulable	kubectl uncordon $NDOE_NAME
Drain node in preparation for maintenance	kubectl drain $NODE_NAME

Namespace & Security

Name	Command
List authenticated contexts	kubectl config get-contexts, ~/.kube/config
Set namespace preference	kubectl config set-context <context_name> --namespace=<ns_name>
Load context from config file	kubectl get cs --kubeconfig kube_config.yml
Switch context	kubectl config use-context <cluster-name>
Delete the specified context	kubectl config delete-context <cluster-name>
List all namespaces defined	kubectl get namespaces
List certificates	kubectl get csr
Check user privilege	kubectl –as=system:serviceaccount:ns-denny:test-privileged-sa -n ns-denny auth can-i use pods/list
Check user privilege	kubectl auth can-i use pods/list
Reference	Link: kubernetes yaml templates

Network

Name	Command
Temporarily add a port-forwarding	kubectl port-forward redis-134 6379:6379
Add port-forwaring for deployment	kubectl port-forward deployment/redis-master 6379:6379
Add port-forwaring for replicaset	kubectl port-forward rs/redis-master 6379:6379
Add port-forwaring for service	kubectl port-forward svc/redis-master 6379:6379
Get network policy	kubectl get NetworkPolicy

Patch

Name	Summary
Patch service to loadbalancer	kubectl patch svc $svc_name -p '{"spec": {"type": "LoadBalancer"}}'

Extenstions

Name	Summary
Enumerates the resource types available	kubectl api-resources
List api group	kubectl api-versions
List all CRD	kubectl get crd
List storageclass	kubectl get storageclass

Components & Services

Services on Master Nodes

Name	Summary
kube-apiserver	exposes the Kubernetes API from master nodes
etcd	reliable data store for all k8s cluster data
kube-scheduler	schedule pods to run on selected nodes
kube-controller-manager	node controller, replication controller, endpoints controller, and service account & token controllers

Services on Worker Nodes

Name	Summary
kubelet	makes sure that containers are running in a pod
kube-proxy	perform connection forwarding
Container Runtime	Kubernetes supported runtimes: Docker, rkt, runc and any OCI runtime-spec implementation.

Addons: pods and services that implement cluster features

Name	Summary
DNS	serves DNS records for Kubernetes services
Web UI	a general purpose, web-based UI for Kubernetes clusters
Container Resource Monitoring	collect, store and serve container metrics
Cluster-level Logging	save container logs to a central log store with search/browsing interface

Tools

Name	Summary
kubectl	the command line util to talk to k8s cluster
kubeadm	the command to bootstrap the cluster
kubefed	the command line to control a Kubernetes Cluster Federation
Kubernetes Components	Link: Kubernetes Components