kubectl lets you control the Kubernetes Cluster Manager.

https://kubernetes.io/docs/reference/kubectl/kubectl/

 

Quick tips

create – creates resources

get – get resources

apply – applies resources

 

Common Commands

See also the kubectl Cheat Sheet: https://kubernetes.io/docs/reference/kubectl/cheatsheet/

 

Show config: k config view

 

To switch to a non-VT cluster (e.g. minikube), need to:

kubectl config get-contexts

k config use-context minikube

 

And view cluster-info or nodes (e.g. to check) with:

Cluster info: k cluster-info

List nodes: k get nodes

Show deployments: k get deployments

List contexts: k config get-contexts

 

 

Pods

Get all pods: k get pods

Describe all pods: k describe pods

Describe pod: k describe pods <pod name>

Listing all pods:

export POD_NAME=$(kubectl get pods -o go-template –template ‘{{range .items}}{{.metadata.name}}{{“\n”}}{{end}}’)

echo Name of the Pod: $POD_NAME

E.g. get output from pod using proxy

k proxy

curl http://localhost:8001/api/v1/namespaces/default/pods/<name of pod>/proxy/

Logs from Pod: k logs $POD_NAME

 

Services

List services: k get services

Describe service: k describe services/kubernetes-bootcamp

Docs

See also this great tutorial: https://kubernetes.io/docs/tutorials/kubernetes-basics/explore/explore-interactive/

and Cheat Sheet: https://kubernetes.io/docs/tasks/debug-application-cluster/get-shell-running-container/

 

Command Summary

If you run kubectl without any arguments you’ll get some information about it. E.g. some commands:

 

Following examples assume we’ve got the name of the Pod in $POD_NAME, e.g. using:

export POD_NAME=$(kubectl get pods -o go-template --template '{{range .items}}{{.metadata.name}}{{"\n"}}{{end}}')

(for more on Go templates see Go: templates

 

Commands – details

apply

Apply additional changes.

Note: this warning can be ignore:

Warning: kubectl apply should be used on resource created by either kubectl create --save-config or kubectl apply

config view

Shows kubeconfig settings which you can query. E.g.

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

https://kubernetes.io/docs/reference/kubectl/cheatsheet/#kubectl-context-and-configuration

create

Create resources

delete

Deletes resources.

https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands#delete

Note that deleting a service does not stop an app running inside a container.

describe

Shows details of a resource.

https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands#describe

E.g.

kubectl describe deploy <deployment name>

exec

Run commands on the container.

https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands#exec

E.g. to see environment variables:

kubectl exec $POD_NAME env

Or to get a terminal:

kubectl exec -it $POD_NAME bash

https://kubernetes.io/docs/tasks/debug-application-cluster/get-shell-running-container/

expose

Creates and exposes a new service to traffic.

Note: --type can be:

• ClusterIP
• NodePort
• LoadBalancer
• ExternalName.

Default is ClusterIP.

E.g. kubectl expose deployment/kubernetes-bootcamp –type=”NodePort” –port 8080

Running kubectl get services shows the new service.

List the port with describe services/kubernetes-bootcamp.

https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands#expose

get

Gets resources. E.g. for deployments:

get deployments

Services:

get services

Or pods:

get pods

Note: for a wider format use -o wide.

And for much, much more detail use: -o yaml. e.g.

kubectl get pods -o yaml.

To narrow it down you probably want to use the name of your pod as well. E.g.

kubectl get pods emoji-6fc8785888-gjd8r -o yaml

https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands#get

Note: you can specify the output as ‘template’ and provide a Go template as the value of the --template flag, to filter the attributes of the fetched resources. E.g.

kubectl get pods -o go-template --template '{{range .items}}{{.metadata.name}}{{"\n"}}{{end}}'

Or

kubectl get pods emoji-6fc8785888-gjd8r -o jsonpath --template={.status.podIP}

for the IP address of a Pod.

For more on Go Templates see: https://golang.org/pkg/text/template/

 

 

Use --no-headers for no headers. E.g. if you want to pipe into awk.

logs

Prints logs for a container in a pod.

Anything the application sends to STDOUT becomes the logs for the container.

https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands#logs

proxy

Creates a proxy (note: this is blocking so need to run it in a new terminal) that forwards communications into the cluster-wide private network which we can query directly using the API. E.g.

curl http://localhost:8001/version

https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands#proxy

rollout

Manage the rollout of a resource. E.g.

kubectl rollout status deployments/kubernetes-bootcamp

https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands#rollout

Or

kubectl rollout status deployment <name of deployment>

 

And view the history with:

kubectl rollout history deployment <name of deployment>

Note: to make sure rollouts are recorded use --record=true. E.g.

kubectl apply --filename=deploy.yml --record=true

run

runNAME –image=… –port=…

This:

• searches for a node
• schedules the application (i.e. the image) to run on that node
• configures the cluster to the instance on a new node when needed
• gives it a NAME to refer to this running image

https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands#run

Notes: this is the iterative method.

 

More on run:

Using:

kubectl run bandicoot-prod --image=gcr.io/kuar-demo/kuard-amd64:2 --replicas=2 --port=8080 --labels="ver=2,app=bandicoot,env=prod"

gives:
kubectl run --generator=deployment/apps.v1beta1 is DEPRECATED and will be removed in a future version. Use kubectl create instead.

What’s this all about?

TLDR: it’s not kubectl run that’s being deprecated. Just the generator --generator= part. But, maintainers are trying to move people over to using kubectl create rather than kubectl run as the run code is messy and complex.

https://stackoverflow.com/questions/52890718/kubectl-run-is-deprecated-looking-for-alternative/53010591#53010591

 

scale

Sets a new size. E.g. number of pods in a deployment.

Trying this on kubernetes.io I scaled beyond capacity and got:

Unable to connect to the server: net/http: TLS handshake timeout

https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands#scale

set

Configure application resources – e.g. to update a deployment

See also Kubernetes: update a deployed application and rollback

https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands#set

 

Errors / Problems

The connection to the server 192.168.99.100:8443 was refused – did you specify the right host or port?

Did you start your Kubernetes cluster? E.g. if you’re using minikube then:

minikube start