sathishmr/cheatsheet-kubernetes-a4

:book: Kubernetes CheatSheets In A4

1 Kubernets CheatSheet

Blog URL: https://cheatsheet.dennyzhang.com/cheatsheet-kubernetes, Category: kubernetes

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See more CheatSheets from Denny: #denny-cheatsheets

1.1 Common Usage

1.1.1 yaml templates

Name	Summary
Pod yaml examples	pod-dummy.yaml, pod-nginx.yaml, pod-volume-redis.yaml
Pod yaml examples	pod-healthcheck-nginx.yaml, pod-gitclone.yaml, pod-handlers.yaml
Deployment yaml examples	deployment-nginx.yaml
Service yaml examples	service-clusterip-nginx.yaml
Statefulset yaml examples	statefulset-nginx.yaml, statefulset-single-mysql, statefulset-replicated-mysql
Serviceaccount yaml examples	serviceaccount-default.yaml
Volume yaml examples	pod-volume-empty-redis.yaml

1.1.2 Common Commands

Name	Command
Validate yaml file with dry run	kubectl create --dry-run --validate -f pod-dummy.yaml
Start a temporary pod to run wget test	kubectl run --rm wget-test --image=busybox --restart=Never --tty -i
Start a temporary pod to run curl test	kubectl run --rm curl-test --image=yauritux/busybox-curl --tty -i
Open a bash terminal in a pod	kubectl exec -it storage sh
Check pod environment variables	kubectl exec redis-master-ft9ex env
Get all services for all namespace	kubectl get service --all-namespaces
Get system conf via configmap	kubectl -n kube-system get cm kubeadm-config -o yaml
Query healthcheck endpoint	curl -L http://127.0.0.1:10250/healthz

1.1.3 Check Performance

Name	Command
Get node resource usage	kubectl top node
Get node resource usage	kubectl top pod
List resource utilization for all containers	kubectl top pod --all-namespaces --containers=true

1.2 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 -o yaml
Get pod info	kubectl describe pod srv-mysql-server
List all pods with labels	kubectl get pods --show-labels
Get Pod initContainer status	kubectl get pod dummy –template ‘{{.status.initContainerStatuses}}’
Get pod by selector	podname=$(kubectl get pods -n $namespace –selector=”app=syslog” -o jsonpath=’{.items[*].metadata.name}’)
List pods with docker images	kubectl get pods -o=jsonpath=’{range .items[*]}{.metadata.name}:{.spec.containers[0].name}{“\t”}{.spec.containers[0].image}{“\n”}{end}’
kubectl run command	kubectl exec -it -n “$namespace” “$podname” – sh -c “echo $msg >>/dev/termination-log”

• Delete Pod

Name	Command
Delete pod	kubectl delete pod hello-node-95913-n63qs
Delete pod by label	kubectl delete pod -l env=test

1.3 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://www.dennyzhang.com

1.4 Deployment & Scale

link: Pausing and Resuming a Deployment

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

1.5 Service

Name	Command
List all services	kubectl get services
Get service detail	kubectl get service nginx-service -o yaml
Get service cluster ip	kubectl get service nginx-service -o go-template=’{{.spec.clusterIP}}’
Get service cluster port	kubectl get service nginx-service -o go-template=’{{(index .spec.ports 0).port}}’

1.6 StatefulSet

Name	Command
List statefulset	kubectl get sts
Scale statefulset	kubectl scale sts <stateful_set_name> --replicas=5
Delete statefulset only (not pods)	kubectl delete sts <stateful_set_name> --cascade=false

1.7 Volumes & Volume Claims

Name	Command
Check the mounted volumes	kubectl exec storage ls /data
Check persist volume	kubectl describe pv pv0001

1.8 Other Components

1.8.1 Log files

Name	Command
API Server.log= in master node	/var.log=/kube-apiserver.log
Scheduler.log= in master node	/var.log=/kube-scheduler.log
Controller.log= in master node	/var.log=/kube-controller-manager.log
Kubelet.log= in worker node	/var.log=/kubelet.log
Kube Proxy.log= in worker node	/var.log=/kubelet-proxy.log

1.8.2 Events & Metrics

Name	Command
View all events	kubectl get events --all-namespaces

1.8.3 Namespace & Security

Name	Command
List authenticated contexts	kubectl config get-contexts
List contexts	kubectl config get-contexts
Switch context	kubectl config use-context <cluster-name>
List all namespaces defined	kubectl get namespaces
kubectl config file	~/.kube/config

1.8.4 Network

Name	Command
Temporarily add a port-forwarding	kubectl port-forward redis-izl09 6379

1.8.5 Endpoint

Name	Command
List endpoints	kubectl get endpoints

1.9 Basic

1.9.1 Key Concepts

Name	Summary
CNCF	Cloud Native Computing Foundation
CRI	Container Runtime Interface
CNI	Container Network Interface
CSI	Container Storage Interface

1.9.2 Kubernets Critical 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
Kubernets working dir	/var/lib/kubelet/
Docker working dir	/var/lib/docker/
Etcd working dir	/var/lib/etcd/
Network cni	/etc/cni/net.d/
Docker container log	/var/log/containers/
Log files	/var/log/pods/
Env	export KUBECONFIG=/etc/kubernetes/admin.conf
Env	/etc/systemd/system/kubelet.service.d/10-kubeadm.conf

1.9.3 Check status

Name	Summary
Start a service	kubectl run hello --image=my_img --port=80
Similar to docker ps	kubectl get nodes
Similar to docker inspect	kubectl describe pod nginx-app-413181-cn
Similar to docker logs	kubectl logs
Similar to docker exec	kubectl exec
Get deployment info	kubectl get deploy
Delete service	kubectl delete service nginxservice
Get kubectl version	kubectl version
Get cluster info	kubectl cluster-info
Get configuration	kubectl config view
Get component status	kubectl get componentstatus
Get node status	kubectl describe node $node_name
Get services for current namespace	kubectl get svc

1.9.4 Kubernetes Developer Resources

Name	Summary
API Conventions	https://github.com/kubernetes/community/blob/master/contributors/devel/api-conventions.md

1.10 Minikube

link: minikube in GitHub

Name	Command
Start minikube env	minikube start
minikube docker-env	eval $(minikube docker-env)
Get dashboard	minikube dashboard
ssh to minikube vm	minikube ssh
Get ip	minikube ip
Get cluster info	kubectl cluster-info
List addons	minikube addons list
Get service info	minikube service $srv_name

TODO: rolling-update command is imperative, better use Deployments rollout. It’s declarative.

1.11 Misc scripts

• Tail pod log by label

namespace="mynamespace"
mylabel="app=mylabel"
kubectl get pod -l "$mylabel" -n "$namespace" | tail -n1 \
    | awk -F' ' '{print $1}' | xargs -I{} \
      kubectl logs -n "$namespace" -f {}

• Get node hardware resource utilization

kubectl get nodes --no-headers \
     | awk '{print $1}' | xargs -I {} \
     sh -c 'echo {}; kubectl describe node {} | grep Allocated -A 5'

kubectl get nodes --no-headers | awk '{print $1}' | xargs -I {} \
    sh -c 'echo {}; kubectl describe node {} | grep Allocated -A 5 | grep -ve Event -ve Allocated -ve percent -ve -- ; echo'

• Apply the configuration in manifest.yaml and delete all the other configmaps that are not in the file.

kaubectl apply --prune -f manifest.yaml --all --prune-whitelist=core/v1/ConfigMap

1.12 More Resources

License: Code is licensed under MIT License.

• Useful links

- https://kubernetes.io/docs/reference/kubectl/cheatsheet/
- https://github.com/kubecamp/kubernetes_in_2_days
- https://marc.xn--wckerlin-0za.ch/computer/kubernetes-on-ubuntu-16-04
- https://codefresh.io/kubernetes-guides/kubernetes-cheat-sheet/