what is kubectl
install
[!NOTE] references:
info:
$ uname | awk '{print tolower($0)}' darwin $ curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt v1.26.2
$ curl -LO https://storage.googleapis.com/kubernetes-release/release/`curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt`/bin/$(uname | awk '{print tolower($0)}')/amd64/kubectl
$ chmod +x ./kubectl
$ sudo mv ./kubectl /usr/local/bin/kubectl
# verify
$ kubectl version --client --short
Flag --short has been deprecated, and will be removed in the future. The --short output will become the default.
Client Version: v1.25.3
Kustomize Version: v4.5.
kubectl-convert
[!NOTE] A plugin for Kubernetes command-line tool kubectl, which allows you to convert manifests between different API versions. This can be particularly helpful to migrate manifests to a non-deprecated api version with newer Kubernetes release.
# intel $ curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/darwin/amd64/kubectl-convert" # apple silicon $ curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/darwin/arm64/kubectl-convert" $ chmod +x ./kubectl-convert $ sudo mv ./kubectl-convert /usr/local/bin/kubectl-convert $ sudo chown root: /usr/local/bin/kubectl-convertsha256 check
$ curl -LO https://storage.googleapis.com/kubernetes-release/release/`curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt`/bin/$(uname | awk '{print tolower($0)}')/amd64/kubectl $ curl -LO https://storage.googleapis.com/kubernetes-release/release/`curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt`/bin/$(uname | awk '{print tolower($0)}')/amd64/kubectl.sha256 $ echo "$(cat kubectl.sha256) kubectl" | shasum -a 256 --check
osx
# intel
$ curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/darwin/amd64/kubectl"
# apple silicon
$ curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/darwin/arm64/kubectl"
# or via brew
$ brew install kubectl
completion
[!NOTE] The Homebrew installation of bash-completion v2 sources all the files in the
BASH_COMPLETION_COMPAT_DIRdirectory, that's why the latter two methods work
$ brew install bash-completion # Bash 3.2
$ brew install bash-completion@2 # Bash 4.1+
$ kubectl completion bash > $(brew --prefix)/etc/bash_completion.d/kubectl
linux
$ curl -LO https://storage.googleapis.com/kubernetes-release/release/`curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt`/bin/$(uname | awk '{print tolower($0)}')/amd64/kubectl
$ chmod +x ./kubectl
$ sudo mv ./kubectl /usr/local/bin/kubectl
completion
$ echo 'source <(kubectl completion bash)' >> ~/.bash_profile
$ kubectl completion bash > /usr/local/etc/bash_completion.d/kubectl
$ echo 'alias k=kubectl' >> ~/.bash_profile
$ echo 'complete -o default -F __start_kubectl k' >> ~/.bash_profile
windows
> choco install kubernetes-cli
> cd %USERPROFILE%
> mkdir .kube
> touch .kube/config
get
reference:
- output options:
-o custom-columns=<header>:<jsonpath>[,<header>:<jsonpath>]...
get all
$ kubectl get all -A
get cluster status
$ kubectl get cs
NAME STATUS MESSAGE ERROR
controller-manager Healthy ok
scheduler Healthy ok
etcd-1 Healthy {"health":"true"}
etcd-2 Healthy {"health":"true"}
etcd-0 Healthy {"health":"true"}
get po
- name
$ kubectl -n devops get po -o custom-columns='NAME:metadata.name' or
$ kubectl -n devops get deploy jenkins -o custom-columns="NAME:metadata.name, IMAGES:..image" NAME IMAGES jenkins jenkins/jenkins:2.187-
$ kubectl get pod -o=custom-columns=NAME:.metadata.name,STATUS:.status.phase,NODE:.spec.nodeName \ --all-namespaces sort pods by nodeName
$ kubectl get pods -o wide --sort-by="{.spec.nodeName}"sort by restart count
$ kubectl get pods --sort-by="{.status.containerStatuses[:1].restartCount}"sort by age
$ kubectl get replicasets -o wide --sort-by=.metadata.creationTimestamp
get all images
$ kubectl get pods --all-namespaces \
-o jsonpath="{..image}" |
tr -s '[[:space:]]' '\n' |
sort |
uniq -c
list
list image from a single deploy
$ kubectl -n devops get deployment jenkins -o=jsonpath='{.spec.template.spec.containers[:1].image}'
jenkins/jenkins:2.187
- or
$ kubectl -n devops get deploy jenkins -o jsonpath="{..image}" jenkins/jenkins:2.187
list Container images by Pod
$ kubectl get pods --all-namespaces -o=jsonpath="{..image}" -l app=nginx
-
$ kubectl -n <namespace> get po \ -o custom-columns='NAME:metadata.name,IMAGES:spec.containers[*].image' -
$ kubectl -n <namespace> get po <pod_name> -o jsonpath="{..containerID}" # or $ kubectl -n <namespace> get po <pod_name> \ -o go-template \ --template="{{ range .status.containerStatuses }}{{ .containerID }}{{end}}"
list all Container images in all namespaces
$ kubectl get pods --all-namespaces -o jsonpath="{.items[*].spec.containers[*].image}"
- or
$ kubectl get pods --all-namespaces -o jsonpath="{..image}" | tr -s '[[:space:]]' '\n' | sort | uniq -c
list Container images filtering by Pod namespace
$ kubectl -n kube-system get pods -o jsonpath="{..image}"
list Container images using a go-template instead of jsonpath
$ kubectl get po --all-namespaces \
-o go-template \
--template="{{range .items}}{{range .spec.containers}}{{.image}} {{end}}{{end}}"
- or
$ kubectl get deploy \ -o=jsonpath="{range .items[*]}{'\n'}{.metadata.name}{':\t'}{range .spec.template.spec.containers[*]}{.image}{', '}{end}{end}"
list all quota
$ for _i in $(kubectl get ns --no-headers | awk -F' ' '{print $1}'); do
echo ------------- ${_i} ------------
kubectl -n ${_i} describe quota
done
check api server healthy
$ kubectl get apiservice
- delete apiservers
$ kubectl delete apiservice v1beta1.metrics.k8s.io
get apiservers
$ kubectl get --raw=/apis
get apiresources
check available
$ kubectl api-resources $ kubectl api-versionscheck apiservices registered
$ kubectl get apiservices.apiregistration.k8s.io $ kubectl get apiservices.apiregistration.k8s.io v1beta1.metrics.k8s.io -o yaml$ kubectl get apiservices.apiregistration.k8s.io NAME SERVICE AVAILABLE AGE v1. Local True 4y v1.apps Local True 4y v1.authentication.k8s.io Local True 4y v1.authorization.k8s.io Local True 4y v1.autoscaling Local True 4y v1.batch Local True 4y v1.monitoring.coreos.com Local True 168d v1.networking.k8s.io Local True 4y v1.rbac.authorization.k8s.io Local True 4y v1.storage.k8s.io Local True 4y v1beta1.admissionregistration.k8s.io Local True 4y v1beta1.apiextensions.k8s.io Local True 4y v1beta1.apps Local True 4y v1beta1.authentication.k8s.io Local True 4y v1beta1.authorization.k8s.io Local True 4y v1beta1.batch Local True 4y v1beta1.certificates.k8s.io Local True 4y v1beta1.coordination.k8s.io Local True 4y v1beta1.events.k8s.io Local True 4y v1beta1.extensions Local True 4y v1beta1.metrics.k8s.io kube-system/metrics-server False (ServiceNotFound) 188d v1beta1.policy Local True 4y v1beta1.rbac.authorization.k8s.io Local True 4y v1beta1.scheduling.k8s.io Local True 4y v1beta1.storage.k8s.io Local True 4y v1beta2.apps Local True 4y v2beta1.autoscaling Local True 4y v2beta2.autoscaling Local True 4y0 $ kubectl get apiservices.apiregistration.k8s.io v1beta1.metrics.k8s.io -o yaml --export apiVersion: apiregistration.k8s.io/v1 kind: APIService metadata: name: v1beta1.metrics.k8s.io spec: group: metrics.k8s.io groupPriorityMinimum: 100 insecureSkipTLSVerify: true service: name: prometheus-adapter namespace: monitoring version: v1beta1 versionPriority: 100 status: conditions: - lastTransitionTime: 2022-08-15T14:10:39Z message: all checks passed reason: Passed status: "True" type: Availabletroubleshooting
[!NOTE|label:references:]
$ kubectl api-resources error: unable to retrieve the complete list of server APIs: metrics.k8s.io/v1beta1: the server is currently unable to handle the request$ kubectl get apiservices.apiregistration.k8s.io NAME SERVICE AVAILABLE AGE v1beta1.metrics.k8s.io kube-system/metrics-server False (ServiceNotFound) 188d # remove metrics.k8s.io $ kubectl delete apiservices.apiregistration.k8s.io v1beta1.metrics.k8s.io # debug $ kubectl get secrets $(kubectl -n kube-system get sa metrics-server -o 'jsonpath={.secrets[].name}') Error from server (NotFound): secrets "metrics-server-token-mr49q" not found $ kubectl get secrets $(kubectl -n kube-system get sa metrics-server -o 'jsonpath={.secrets[].name}') \ -o "jsonpath={.data.ca\.crt}" | base64 -d | openssl x509 -text -noout | grep Not # get token $ kubectl get secrets $(kubectl -n kube-system get sa metrics-server -o 'jsonpath={.secrets[].name}') \ -o "jsonpath={.data.token}" | base64 -d -w0 # get namespace $ kubectl get secrets $(kubectl -n kube-system get sa metrics-server -o 'jsonpath={.secrets[].name}') \ -o "jsonpath={.data.namespace}" | base64 -d -w0
check etcd
$ kubectl get --raw=/healthz/etcd
ok
output format
[!NOTE|label:references:]
apply
[!NOTE|label:referenecs]
oneline cmd
$ cat << EOF | kubectl create -f - apiVersion: v1 kind: Secret metadata: name: mysecret type: Opaque data: password: $(echo "admin" | base64) username: $(echo "1f2d1e2e67df" | base64) EOF-
# Edit the last-applied-configuration annotations by type/name in YAML kubectl apply edit-last-applied deployment/nginx # Edit the last-applied-configuration annotations by file in JSON kubectl apply edit-last-applied -f deploy.yaml -o json
rollback
[!NOTE|label:references:] -** How do you rollback deployments in Kubernetes?