Kubernetes Cheat Sheet for Simplifying Container Orchestration

Kubernetes is an open-source container-orchestration system for automating application deployment, scaling, and management. It was originally designed by Google and is now maintained by the Cloud Native Computing Foundation.

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`
Show nodes with labels	`kubectl get nodes --show-labels`
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` `https://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’`
Ubuntu install kubectl	`"deb` `https://apt.kubernetes.io/` `kubernetes-xenial main"`

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 statefulset 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 running pods	`kubectl get pods –field-selector=status.phase=Running`
Get Pod initContainer status	`kubectl get pod --template '{.status.initContainerStatuses}' <pod-name>`
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’`

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`

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`

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`
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}’`
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`

Secrets

Name	Command
List secrets	`kubectl get secrets --all-namespaces`
Generate secret	`echo -n 'mypasswd'`, then redirect to `base64 -decode`
Create secret from cfg file	`kubectl create secret generic db-user-pass –from-file=./username.txt`

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`

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`

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`

Network

Name	Command
Temporarily add a port-forwarding	`kubectl port-forward redis-izl09 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
List api group	`kubectl api-versions`
List all CRD	`kubectl get crd`
List storageclass	`kubectl get storageclass`
List all supported resources	`kubectl api-resources`

Components & Services

1. 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

2. 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.

3. 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

4. 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

Thanks for reading to the end; I hope you gained some knowledge. ❤️🙌

- Rushikesh Mashidkar💕

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