Kubernetes Cheat Sheet

Tổng hợp các câu lệnh cơ bản khi sử dụng kubectl để vận hành cụm kuberentes.

Pods

List all pods in namespace <default>

kubectl get pods

hoặc

kubectl get pod

hoặc

kubectl get po

View a pod in watch mode

kubectl get pod <pod> --watch

View all pods in watch mode

kubectl get pods -A --watch

List sroted pods

kubectl get pods --sort-by='.status.containerStatuses[0].restartCount'

List pods using a different output

kubectl get pods -o <json|yaml|wide|custom-columns=...|custom-columns-file=...|go-template=...|go-template-file=...|jsonpath=...|jsonpath-file=...>

Ví dụs:

• JSON output

kubectl get pods -o json

Hoặc

kubectl get pods -ojson

Hoặc

kubectl get pods -o=json

• Wide output:

kubectl get pods -o wide

• Custom columns:

kubectl get pods -o custom-columns='DATA:spec.containers[*].image'

Hoặc

kubectl get pods -o custom-columns='DATA:spec.containers[*].volumeMounts'

Hoặc

kubectl get pods -o custom-columns='DATA:metadata.*'

Formatting output

Bạn muốn output của câu lệnh theo format gì, sử dụng các tủy chọn như bên dưới:

Output format	Description
-o=custom-columns=<spec>	Print a table using a comma separated list of custom columns
-o=custom-columns-file=<filename>	Print a table using the custom columns template in the file<filename>
-o=json	Output a JSON formatted API object
-o=jsonpath=<template>	Print the fields defined in a jsonpath expression
-o=jsonpath-file=<filename>	Print the fields defined by the jsonpath expression in the file<filename>
-o=name	Print only the resource name and nothing else
-o=wide	Output in the plain-text format with any additional information, and for pods, the node name is included
-o=yaml	Output a YAML formatted API object

List all pods in a namespace

kubectl get pods -n <namespace>

Hoặc

kubectl -n <namespace> get pods 

Hoặc

kubectl --namespace <namespace> get pods 

List all pods in all namespaces

kubectl get pods --all-namespaces

Hoặc

kubectl get pods -A

Create pod from an image

kubectl run <pod> --generator=run-pod/v1 --image=<image>

Trong cheat sheet này chúng ta sẽ dùng image nginx hoặc busybox.

Ví dụ:

kubectl run nginx --generator=run-pod/v1 --image=nginx

kubectl run busybox --generator=run-pod/v1 --image=busybox

Run pod in an interactive shell mode

kubectl run -i --tty nginx --image=nginx -- sh 

Run a command after creating a pod

kubectl run busybox --image=busybox -- sleep 100000

Executing a command in a running pod

kubectl exec <pod> -- <command>

Hoặc pass stdin to the container in TTY mode:

kubectl exec -it <pod> -- <command>

Ví dụ:

kubectl exec -it nginx -- ls -lrth /app/

Create a pod: dry run mode (không thực sự tạo pod, chỉ chạy ở loca mà không tạo trên server)

kubectl run <pod> --generator=run-pod/v1 --image=nginx --dry-run=client

Patch a pod

kubectl patch pod <pod> -p '<patch>'

Ví dụ:

kubectl patch pod <pod> -p  '{"spec":{"containers":[{"name":"kubernetes-serve-hostname","image":"new image"}]}}'

Ví dụ khác:

kubectl patch pod valid-pod --type='json' -p='[{"op": "replace", "path": "/spec/containers/0/image", "value":"new image"}]'

Create from a YAML file

kubectl create -f pod.yaml

Export YAML from the dry run mode

kubectl run nginx --generator=run-pod/v1 --image=nginx --dry-run -o yaml

Create from STDIN

cat <<EOF | kubectl create -f -
apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
spec:
  containers:
  - name: nginx
    image: nginx:latest
EOF

Create multiple resources from STDIN

cat <<EOF | kubectl create -f -
apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
spec:
  containers:
  - name: nginx
    image: nginx:latest
---
apiVersion: v1
kind: Pod
metadata:
  name: busybox
spec:
  containers:
  - name: busybox
    image: busybox
    args:
    - sleep
    - "100"

Create in a namespace

kubectl run nginx --generator=run-pod/v1 --image=nginx -n <namespace>

Create in a namespace from a file

kubectl create -f pod.yaml -n <namespace>

Delete pods

kubectl delete pod/<pod>

Hoặc

kubectl delete pod <pod> 

Nếu bạn tạo pod từ file yaml, bạn có thể dùng:

kubectl delete -f pod.yaml 

To force deletion:

kubectl delete pod <pod> --grace-period=0 --force

Get pod logs

kubectl logs <pod>

Hoặc

Đôi khi bạn chạy nhiều container trong một pod, bạn sẽ cần phải chọn container để xem log:

kubectl logs <pod> -c <container>

Để follow output log (tail -f):

kubectl logs -f <pod>

Lấy log của nhiều pod thông qua label:

kubectl logs -l <label_name>=<label_value>

Ví dụ:

kubectl logs -l env=prod

Bạn có thể xem log của nhiều container qua label:

kubectl logs -l <label_name>=<label_value> -c <container>

Hoặc view all containers logs với label:

kubectl logs -f -l <label_name>=<label_value> --all-containers

List all container id of init container of all pods

kubectl get pods --all-namespaces -o jsonpath='{range .items[*].status.initContainerStatuses[*]}{.containerID}{"\n"}{end}' | cut -d/ -f3

Show metrics for a given pod

kubectl top pod <pod>

Show metrics for a given pod and all its containers

kubectl top pod <pod> --containers               

Deployments

Tạo một deployment

kubectl create deployment <deployment> --image=<image> -n <namespace>

Tạo deployment với định nghĩa số replica

kubectl create deployment <deployment> --image=<image> --replicas=<number> -n <namespace>

Tạo deployment với số pod và port được định nghĩa trước

kubectl create deployment <deployment> --image=<image> --replicas=<replicas> --port=<port> -n <namespace>

Ví dụ:

kubectl create deployment nginx --image=nginx --replicas=2 --port=80

Tạo deployment với số pod và port được định nghĩa trước và expose nó

kubectl create deployment nginx --image=nginx --replicas=2 --port=80 --expose

Get a deployment

kubectl get deploy <deployment>

Watch a deployment

kubectl get deployment <deployment> --watch

Hoặc

kubectl get deployment <deployment> -w

Hoặc using a shorter version:

kubectl get deploy <deployment> -w

Hoặc dài hơn:

kubectl get deployments.apps <deployment> --watch

List all deployments

Giống như việc list các pod, namespace hay service, chúng ta dùng giống một format:

kubectl get deploy -n <namespace>

kubectl get deploy --all-namespaces 
kubectl get deploy -A

kubectl get deploy -o yaml
kubectl get deploy -o wide

Update the image

Rolling update “nginx” containers của “nginx” deployment, updating image:

kubectl set image deployment/nginx nginx=nginx:1.9.1

Rolling update “api” containers của “backend” deployment, updating image:

kubectl set image deployment/backend api=image:v2

Scale a deployment

kubectl scale --replicas=5 deployment/<deployment>

Note: Bạn có thể dùng cách ngắn hơn:

kubectl scale --replicas=5 deploy/<deployment>

Dry run và YAML output

kubectl create deployment nginx --image=nginx --replicas=2 --port=80 --dry-run -o yaml

Tạo một deployment từ một file

kubectl apply -f deployment.yaml

Edit a deployment

kubectl edit deployment/<deployment>

Rollback deployment

Sau khi chỉnh sửa deployment, nếu bị lỗi thì bạn có thể rollback về thay đổi trước đó:

kubectl rollout undo deployment <deployment>

Get rollout history

Bạn có thể xem rollout history:

kubectl rollout history deployment <deployment>

kubectl rollout history deployment <deployment>

Ví dụ:

kubectl rollout history deployment nginx

Bạn sẽ nhận được:

REVISION  CHANGE-CAUSE
2         kubectl set image deployment/nginx nginx=nginx:1.9.1 --record=true
3         <none>

Roll back đến một bản sửa đổi trước đó

Sử dụng revison, chúng ta có thể rollback lại thay đổi trước đó:

kubectl rollout undo deployment <deployment> --to-revision=<revision>

Ví dụ:

kubectl rollout undo deployment nginx --to-revision=2

Execute deployment rollout operations

kubectl rollout status deployment <deployment>
kubectl rollout pause deployment <deployment>
kubectl rollout resume deployment <deployment>

Port Forwarding

Chọn localhost port

kubectl port-forward deployment <deployment>  <locahost-port>:<deployment-port>
kubectl port-forward pod <pod>  <locahost-port>:<pod-port>
kubectl port-forward service <service>  <locahost-port>:<service-port>
kubectl port-forward replicaset <replicaset> <locahost-port>:<replicaset-port>

Ví dụ:

Forward port localhost 8090 từ pod 6379:

kubectl port-forward redis 8090:6379

Sử dụng chung port ở local

kubectl port-forward pod <pod> <port>

Ví dụ: Listen on ports 8000 and 9000 on localhost, forwarded from the same ports in the pod (8000 and 9000)

kubectl port-forward pod nginx 8000 9000

Listen trên một random port ở local

kubectl port-forward pod <pod> :<pod-port>

Ví dụ:

kubectl port-forward pod nginx :80

Listen trên port ở localhost + IP khác

kubectl port-forward --address localhost,<IP.IP.IP.IP> pod <pod> <locahost-port>:<pod-port>

Ví dụ:

kubectl port-forward --address localhost,10.10.10.1 pod redis 8090:6379

Listen trên forwarded port trên tất cả địa chỉ

kubectl port-forward --address 0.0.0.0 pod <pod> <hosts-port>:<pod-port>

Services

Create a service

kubectl create service <clusterip|externalname|loadbalancer|nodeport> <service> [flags] [options]>

Ví dụ:

kubectl create service clusterip myclusterip --tcp=5678:8080
kubectl create service  loadbalancer myloadbalancer --tcp=80

Có thể dùng svc thay cho service.

Delete service(s)

kubectl delete service myclusterip
kubectl delete service myloadbalancer

kubectl delete svc myclusterip
kubectl delete svc myloadbalancer

Hoặc

kubectl delete service myclusterip myloadbalancer

Describe a service

kubectl describe service <service>

Nodes

Get node

kubectl get nodes

Get a specific node

kubectl get nodes <node>

Show node metrics

kubectl top node <node>

Get external IPs of cluster nodes

kubectl get nodes -o jsonpath='{.items[*].status.addresses[?(@.type=="ExternalIP")].address}'

Describe commands with verbose output

kubectl describe nodes <node>

Check which nodes are ready

JSONPATH='{range .items[*]}{@.metadata.name}:{range @.status.conditions[*]}{@.type}={@.status};{end}{end}' && kubectl get nodes -o jsonpath="$JSONPATH" | grep "Ready=True"

Mark a node as unschedulable

kubectl cordon <node>

Drain a node for maintenance

kubectl drain <node>

Mark a node as schedulable

kubectl uncordon <node>

Namespaces

List namespaces

kubectl get namespaces 

Hoặc

kubectl get ns 

List hoặc describe a namespace

kubectl get namespace <namespace>
kubectl describe namespace <namespace>

Create namespace

kubectl create namespace <namespace>

Hoặc

kubectl create -f namespace.yaml

Hoặc

cat <<EOF | kubectl create -f -
apiVersion: v1
kind: Namespace
metadata:
  name: mynamespace
EOF

Delete namespace

kubectl delete namespace <namespace> 

Hoặc

kubectl delete -f namespace.yaml

Service accounts

List service accounts

kubectl get serviceaccounts

Hoặc

kubectl get sa

Get a service account

kubectl get serviceaccount <serviceaccount>

Hoặc

kubectl get serviceaccounts <serviceaccount>

Hoặc

kubectl get sa <serviceaccount>

Hoặc

kubectl get sa/<serviceaccount>

Create a service account

kubectl create serviceaccount <serviceaccount>

Delete a service account

kubectl delete serviceaccount <serviceaccount> 

Hoặc

kubectl delete -f myserviceaccount.yaml

Describe a service account

kubectl describe serviceaccount <serviceaccount> 

Events

List events

kubectl get events -A

List sorted events

kubectl get events --sort-by=<JSONPath>

Ví dụ: Sorted by timestamp

kubectl get events --sort-by=.metadata.creationTimestamp

List formatted events

kubectl get events -o <json|yaml|wide|custom-columns=...|custom-columns-file=...|go-template=...|go-template-file=...|jsonpath=...|jsonpath-file=...>

Ví dụ:

kubectl get events -owide

Documentation

Get the documentation for pod manifests

kubectl explain pod

Get the documentation for service manifests

kubectl explain service

Describing resources

kubectl describe <resource> <reosurce_name>

Ví dụ:

kubectl describe pod busybox

Hoặc

kubectl describe nodes minikube 

Other possible resources you can use with :describe

apiservices.apiregistration.k8s.io
certificatesigningrequests.certificates.k8s.io
clusterrolebindings.rbac.authorization.k8s.io
clusterroles.rbac.authorization.k8s.io
componentstatuses
configmaps
controllerrevisions.apps
cronjobs.batch
csidrivers.storage.k8s.io
csinodes.storage.k8s.io
customresourcedefinitions.apiextensions.k8s.io
daemonsets.apps
daemonsets.extensions
deployments.apps
deployments.extensions
endpoints
events
events.events.k8s.io
horizontalpodautoscalers.autoscaling
ingresses.extensions
ingresses.networking.k8s.io
jobs.batch
leases.coordination.k8s.io
limitranges
mutatingwebhookconfigurations.admissionregistration.k8s.io
namespaces
networkpolicies.extensions
networkpolicies.networking.k8s.io
nodes
persistentvolumeclaims
persistentvolumes
poddisruptionbudgets.policy
pods
podsecuritypolicies.extensions
podsecuritypolicies.policy
podtemplates
priorityclasses.scheduling.k8s.io
replicasets.apps
replicasets.extensions
replicationcontrollers
resourcequotas
rolebindings.rbac.authorization.k8s.io
roles.rbac.authorization.k8s.io
runtimeclasses.node.k8s.io
secrets
serviceaccounts
services
statefulsets.apps
storageclasses.storage.k8s.io
validatingwebhookconfigurations.admissionregistration.k8s.io
volumeattachments.storage.k8s.io

Editing resources

Edit a service

kubectl edit service <service>                    

Edit a service with your favorite text editor

KUBE_EDITOR="vim" edit service <service>  

Note: chúng ta có thể thay đổi cho các resource khác như: service, deployment …

Deleting Resources

Delete a resource using the type and name specified in <file>

kubectl delete -f <file>      

Delete pods and services with same names

kubectl delete pod,service <name1> <name2>

Delete pods and services with a custom label

kubectl delete pods,services -l <label-name>=<label-value>

Delete all pods and services in a namespace

kubectl -n <namespace> delete pods,services --all              

Delete all resources in a namespace

kubectl delte <namespace>

All get commands

kubectl get all
kubectl get pods
kubectl get replicasets
kubectl get services
kubectl get nodes
kubectl get namespaces
kubectl get configmaps
kubectl get endpoints 

Viết tắt của một vài resouce bạn có thể dùng

Resource type	Abbreviations
componentstatuses	cs
configmaps	cm
daemonsets	ds
deployments	deploy
endpoints	ep
event	ev
horizontalpodautoscalers	hpa
ingresses	ing
limitranges	limits
namespaces	ns
nodes	no
persistentvolumeclaims	pvc
persistentvolumes	pv
pods	po
podsecuritypolicies	psp
replicasets	rs
replicationcontrollers	rc
resourcequotas	quota
serviceaccount	sa
services	svc

Verbose Kubectl

kubectl run nginx  --image=nginx --v=5

Verbosity	Description
--v=0	Generally useful for this to always be visible to a cluster operator.
--v=1	A reasonable default log level if you don’t want verbosity.
--v=2	Useful steady state information about the service and important log messages that may correlate to significant changes in the system. This is the recommended default log level for most systems.
--v=3	Extended information about changes.
--v=4	Debug level verbosity.
--v=6	Display requested resources.
--v=7	Display HTTP request headers.
--v=8	Display HTTP request contents.
--v=9	Display HTTP request contents without truncation of contents.

(Table source: K8s docs)

Cluster

Display addresses of the master and services

kubectl cluster-info                        

Dump cluster state to STDOUT

kubectl cluster-info dump           

Dump cluster state to a file

kubectl cluster-info dump --output-directory=</file/path>

Compares the current cluster state against the state that the cluster would be in if the manifest was applied

kubectl diff -f ./my-manifest.yaml

List all images running in a cluster

kubectl get pods -A -o=custom-columns='DATA:spec.containers[*].image'

Kubectl context

Show merged kubeconfig settings

kubectl config view 

Use multiple kubeconfig

KUBECONFIG=~/.kube/config1:~/.kube/config2:~/.kube/config3

Get a list of users

kubectl config view -o jsonpath='{.users[*].name}'

Display the first user

kubectl config view -o jsonpath='{.users[].name}'

Get the password for the “admin” user

kubectl config view -o jsonpath='{.users[?(@.name == "admin")].user.password}'

Display the current context

kubectl config current-context

Display list of contexts

kubectl config get-contexts

Set the default context to <cluster>

kubectl config use-context <cluster>

Sets a user entry in kubeconfig

kubectl config set-credentials <username> [options]

Sets a user with a client key

kubectl config set-credentials <user> --client-key=~/.kube/admin.key

Sets a user with basic auth

kubectl config set-credentials --username=<username> --password=<password>

Sets a user with client certificate

kubectl config set-credentials <user> --client-certificate=<path/to/cert> --embed-certs=true

Set a context utilizing a specific config file

kubectl config --kubeconfig=<config/path> use-context <cluster>

Set a context utilizing a specific username and namespace.

kubectl config set-context gce --user=cluster-admin --namespace=foo \
  && kubectl config use-context gce

Alias

Create an alias on *nix

alias k=kubectl

Create an alias on Windows

Set-Alias -Name k -Value kubectl

Kubectl create và apply

Create

Create khi bạn muốn tạo một deployment, service … mới chưa tồn tại. Nếu chúng đã tồn tại thì bạn sẽ nhận được thông báo lỗi:

kubectl create -f <filename|url>

kubectl delete deployment <deployment-name>
kubectl delete deployment <deployment-filename>
kubectl delete deployment <deployment-url>

Apply

Apply sẽ linh động hơn Create, khi mà resouce cần tại đã có sẵn thì sẽ update những thay đổi, còn chưa có sẽ tạo mới.

kubectl apply -f <filename|url>
kubectl delete -f <deployment-filename>
kubectl apply -f <deployment-filename>