"You run kubectl apply on a Deployment. A few minutes later a Pod is running. Describe in as much detail as possible, the exact chain of events from kubectl apply to the running pod."
kubectl -> client-side validation -> api-server(authentication, authorization, admission control) -> etcd (add Deployment resource) -> api-server -> controller-manager (deployment controller creates hash of pod template and create a ReplicaSet with hash appended to name) -> ReplicaSet reource created -> api-server -> etcd(add ReplicaSet resource) -> api-server -> controller-manager (replicaset controller creates the same number of pods given in replica spec with a random name appended) -> api-server -> etcd(add the pods) -> api-server -> scheduler(find the best possible node for the pods) -> api-server -> Kubelet of the node set by scheduler -> CRI -> Actual Container Runtime(translate pod to actual containers) -> pause container -> CNI -> CNI plugin -> bridge -> veth -> assign IP to pod -> inter-host networking -> container starts running
Run curl test temporarily
kubectl run --generator=run-pod/v1 --rm mytest --image=yauritux/busybox-curl -it
Run wget test temporarily
kubectl run --generator=run-pod/v1 --rm mytest --image=busybox -it wget
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
List authenticated contexts
kubectl config get-contexts, ~/.kube/config
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
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
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
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
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
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
kubectl get pods -o='custom-columns=PODS:.metadata.name,CONTAINERS:.spec.containers\[\*\].name'
Reference
Link: kubernetes yaml templates
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
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
1.8 Quota & Limits & Resource 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
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
Reference
Link: kubernetes yaml templates
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
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
1.12 Volumes & Volume Claims 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
Name
Command
View all events
kubectl get events --all-namespaces
List Events sorted by timestamp
kubectl get events -sort-by=.metadata.creationTimestamp
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
1.15 Namespace & Security List authenticated contexts
kubectl config get-contexts, ~/.kube/config
Set namespace preference
kubectl config set-context <context_name> --namespace=<ns_name>
Switch context
kubectl config use-context <cluster-name>
Load context from config file
kubectl get cs --kubeconfig kube_config.yml
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
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
Name
Summary
Patch service to loadbalancer
kubectl patch svc $svc_name -p '{"spec": {"type": "LoadBalancer"}}'
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
1.19 Components & Services 1.19.1 Services on Master Nodes 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
1.19.3 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
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
