A Developer Cheat-Sheet for kubectl

Some useful kubectl commands. This is only a taster* of common commands, you can also refer to the official Kubernetes Cheat Sheet for many more.

Setting the default namespace

To quickly restrict your commands to a given namespace, e.g. your own Fragalysis Stack deployment you can use the set-context command. If your stack is deployed to stack-alan-default you can set the default namespace to it with the following command: -

$ kubectl config set-context --current --namespace=stack-alan-default

From this point forward you need to add -n stack-alan-default to each command you want to run.

This is probably the most important command to you should run - by setting the default namespace to that for your stack it’ll be much more difficult for you to make the mistake of adjusting the content of namespaces being used by others.

The following cheats assume that you have set the default namespace.

List namespace content

You can see all the (typical)objects in a namespace with the following command: -

$ kubectl get all

It’ll display information about Pods, Services, Jobs, CronJobs, Deployments and StatefulSets. Ironically all doesn’t show you everything.

List more namespace content (PVCs, Secrets, Ingress)

You can display information about any object in a namespace as long as you know what it is you want to see. Some common objects not present in the default set of all objects are volume claims (a pvc), secrets and external ingress paths. You can use recognised abbreviations or the full object name: -

$ kubectl get pvc

$ kubectl get svc

$ kubectl get service

$ kubectl get ing

Or combine them: -

$ kubectl get pvc,svc,ing

Display Pod logs

Kubernetes keeps the stdout of each container in a Pod. The term Pod is implied when using the command so you simply need to provide the name of the Pod, you don’t have to tell Kubernetes it’s a Pod: -

$ kubectl logs stack-0

You can follow logs: -

$ kubectl logs stack-0 -f

You can see the logs from the last 10 minutes, or the last 10 lines: -

$ kubectl logs stack-0 --since=10m

$ kubectl logs stack-0 --tail=10

You can see the logs from the previous container instance, if it exists (in the case of a restarted container): -

$ kubectl logs stack-0 -p

Shell into a Pod container

You can get an interactive container shell in a Pod assuming you know what shell the container is sing (typically bash). To get into a running Fragalysis Stack you can use this command: -

$ kubectl exec -it pod/stack-0 bash

Once you’re done you can ctrl-d to get out of the container.

Port-forwarding

You can access Pod ports from your local machine using the kubectl port-forward command. For example, if you have a database Pod (database-0) using port 5432 in namespace blob you can connect 1234 on your local machine to the Pod with…

kubectl port-forward database-0 -n blob 1234:5432

Then, any local access to port 1234 will be redirected to the Pod.

Watching object state changes

You can watch rolling update status of the stack until completion using the --watch argument

Restarting a Pod (scale down and up)

You can bounce (restart) a container. This won’t normally re-deploy a new image - for that you really need to be using the AWX console. But the following might be useful if you simply want to restart a Pod, which is achieved by scaling down and then back up. Here we scale down the Stack’s StatefulSet before scaling it bak up again.

Remember that restarting a Pod will cause it to loose any data that is not actively persisted.

$ kubectl scale --replicas=0 statefulset/stack

$ kubectl scale --replicas=1 statefulset/stack