Kubectl

Scale all deployments in a namespace in one go

kubectl scale deploy -n <namespace> --replicas=0 --all

Make a secret for your private repository.

This will enable you to use an image in in i.e. Azure, AWS or Google in any other K8 cluster:

kubectl create secret docker-registry my-registry  --docker-email="your@email" --docker-username="your registry username" --docker-server="your registry server address" --docker-password="your registry password"

Create a new secret fropm a file (json or yaml or what not)

kubectl create secret generic secret-name --from-file=secrets.json

Decoding a Secret

kubectl get secret mysecret -o yaml

Decode the password field

echo 'MWYyZDFlMmU2N2Rm' | base64 --decode

Editing a Secret

kubectl edit secrets mysecret

But beware, you then get the secret 64 encoded, and you will have to decode and encode it before updating. Fortunatly there is a very good small python script for that, which you can find here

Get a list of all contexts

kubectl config get-contexts

Switch to another context, which is in your ~/.kube/config file

You can find the names in the ~/.kube/config file.

kubectl config use-context my-context-name

Set the context manually

kubectl config set-context my-context-name

Autocomplete in bash

source <(kubectl completion bash) # setup autocomplete in bash into the current shell, bash-completion package should be installed first.
echo "source <(kubectl completion bash)" >> ~/.bashrc # add autocomplete permanently to your bash shell.

Shorthand alias for kubectl

alias k=kubectl
complete -F __start_kubectl k

Changeing namespace “on the fly”, i.e. not permanently

kubectl --namespace=mynamespace

Setting namespace preference

kubectl config set-context --current --namespace=<insert-namespace-name-here>
# Validate it
kubectl config view --minify | grep namespace:

Se resources in namespaces

# In a namespace
kubectl api-resources --namespaced=true

# Not in a namespace
kubectl api-resources --namespaced=false

All config commands, meaning kubectl config …..and then:

current-context Displays the current-context
delete-cluster  Delete the specified cluster from the kubeconfig
delete-context  Delete the specified context from the kubeconfig
get-clusters    Display clusters defined in the kubeconfig
get-contexts    Describe one or many contexts
rename-context  Renames a context from the kubeconfig file.
set             Sets an individual value in a kubeconfig file
set-cluster     Sets a cluster entry in kubeconfig
set-context     Sets a context entry in kubeconfig
set-credentials Sets a user entry in kubeconfig
unset           Unsets an individual value in a kubeconfig file
use-context     Sets the current-context in a kubeconfig file
view            Display merged kubeconfig settings or a specified kubeconfig file

Easy way to make a secret yaml file from a secret file

kubectl create secret generic my-secret-name \
    --from-file=./my-secret-file.json --dry-run -o yaml |
  kubectl apply -f -

Delete a user from a context

kubectl --kubeconfig=config-demo config unset users.<name>

Rolling restart of a deployment pod.

kubectl rollout restart deployment/<my-deployment>

Get a proxy on your localhost

kubectl proxy

Get a terminal in a busybox image

kubectl run -i --rm  --tty busybox --image=busybox --restart=Never -- sh

Restart a pod in Kubernerest

As of kubernetes 1.15, you can now do a rolling restart of all pods for a deployment, so that you don’t take the service down

kubectl -n <namepace-name> rollout restart deployment <deployment-name>

If you have set the namespace in you config, the namespace is optional

scaling a replica set

kubectl scale --replicas=3 rs/foo

Deployments

For normal deployment:

The dash f “-f” is for “file”

kubectl apply -f my-yaml-deployment.yaml

Dry run, i.e. check everything is ok

kubectl apply --dry-run=server my-yaml-deployment.yaml

Delete unused contexts from the config file

kubectl config unset takes a dot-delimited path. You can delete cluster/context/user entries by name. E.g.

kubectl config unset users.gke_project_zone_name

kubectl config unset contexts.aws_cluster1-kubernetes

kubectl config unset clusters.foobar-baz

Delete configmaps

# kubectl delete configmap  <configmap-name>  -n  <namespace-name>
$ kubectl delete configmap    my-cofigmap     -n   namespacename

Or from yaml

# kubectl delete -f <file-directory> -n <namespace-name>
$ kubectl delete -f  configmap.yaml  -n  namespacename

Get a shell in a running container

Note: The double dash (–) separates the arguments you want to pass to the command from the kubectl arguments.

kubectl exec --stdin --tty shell-demo -- /bin/bash

The syntax of Kubectl cp

Kubectl CP is as simple as a typical Linux CP command. kubectl cp <source-file-path> <destination-file-path>

Here is the syntax to copy a file from local to pod

kubectl cp /<path-to-your-file>/<file-name> <pod-name>:<fully-qualified-file-name> -c <container-name>

Here is the syntax to copy a file from the pod to local

kubectl cp <pod-name>:<fully-qualified-file-name> /<path-to-your-file>/<file-name> -c <container-name>

Getting logs

Getting the logs of the previous pod for a deployment

kubectl logs podname --previous

Getting the logs of a specific container inside a pod

kubectl logs podname -c service-name

Get the logs from a crashing container during container init causing crashloopbackoff

kubectl logs your_podname -c  container_name

Some useful Links

A page with most CLI commands Kubernetes documentation home Kubernetes secrets in genereal