I am kubernetes newbie, and I have a basic question
my understanding from https://kubernetes.io/docs/reference/kubectl/conventions/ is , we can generate yaml templates using "kubernetes run" command
But when I tried doing same, it didn't work as expected
kubectl run deployment-sample --image deployment-sample --dry-run -o yaml --generator=extensions/v1beta1
error: generator "extensions/v1beta1" not found
kubectl run deployment-sample --image deployment-sample --dry-run -o yaml --generator=apps/v1beta1
error: generator "apps/v1beta1" not found
Not sure if my understanding is wrong or something wrong in my command ?
I am on kubernetes 1.11
I find that I can create a Deployment with kubectl run --generator=deployment/v1beta1 foobar --image=nginx -o yaml --dry-run so your case would be kubectl run --generator=deployment/v1beta1 deployment-sample --image=deployment-sample -o yaml --dry-run. The kubectl conventions page you refer to does say this generator is 'recommended' for Deployments.
But I'm not sure why the docs list a non-recommended generator option that actually doesn't work. For a command like this you can recreate the expected output in a reference environment through the online tutorials at https://kubernetes.io/docs/tutorials/kubernetes-basics/create-cluster/cluster-interactive/ You get the same output there so it is not just you or your cluster. My best guess is that 'extensions/v1beta1' is too general to match to a deployment specifically. It could well be that the documentation needs changing on this.
Related
I am looking to apply existing annotations on a Kubernetes resource to the underlying YAML configuration files. For example, this command will successfully find all pods with a label of "app=helloworld" or "app=testapp" and annotate them with "xyz=test_anno":
kubectl annotate pods -l 'app in (helloworld, testapp)' xyz=test_anno
However, this only applies the annotations to the running pods and doesn't change the YAML files. How do I force those changes to the YAML files so they're permanent, either after the fact or as part of kubectl annotate to start with?
You could use the kubectl patch command with a little tricks
kubectl patch $(k get po -l 'app in (helloworld, testapp)') -p '{"metadata":{"annotations":{"xyz":"test_anno"}}}'
I have followed the getting started instructions here: https://linkerd.io/2/getting-started/
Please see the command below:
kubectl kustomize kustomize/deployment | \
linkerd inject - | \
kubectl apply -f -
emojivoto is now installed an accessible as I expected.
How can I remove emojivoto? This appears to work:
kubectl delete -f https://run.linkerd.io/emojivoto.yml
However, is it possible to do this without using an online resource?
This is of course possible: The mentioned yaml consists of multiple object definitions.
For example namespaces and service accounts.
Each of them can be deleted using kubectl delete <type> <name>.
Since all objects are created in the namespace emojivoto it is possible to remove everything by just removing the namespace: kubectl delete namespace emojivoto.
The other option is to save the yaml file locally and use kubectl delete -f <file> instead.
I'd like to diff a Kubernetes YAML template against the actual deployed ressources. This should be possible using kubectl diff. However, on my Kubernetes cluster in Azure, I get the following error:
Error from server (InternalError): Internal error occurred: admission webhook "aks-webhook-admission-controller.azmk8s.io" does not support dry run
Is there something I can enable on AKS to let this work or is there some other way of achieving the diff?
As a workaround you can use standard GNU/Linux diff command in the following way:
diff -uN <(kubectl get pods nginx-pod -o yaml) example_pod.yaml
I know this is not a solution but just workaround but I think it still can be considered as full-fledged replacement tool.
Thanks, but that doesn't work for me, because it's not just one pod
I'm interested in, it's a whole Helm release with deployment,
services, jobs, etc. – dploeger
But anyway you won't compare everything at once, will you ?
You can use it for any resource you like, not only for Pods. Just substitute Pod by any other resource you like.
Anyway, under the hood kubectl diff uses diff command
In kubectl diff --help you can read:
KUBECTL_EXTERNAL_DIFF environment variable can be used to select your
own diff command. By default, the "diff" command available in your
path will be run with "-u" (unified diff) and "-N" (treat absent files
as empty) options.
The real problem in your case is that you cannot use for some reason --dry-run on your AKS Cluster, which is question to AKS users/experts. Maybe it can be enabled somehow but unfortunately I have no idea how.
Basically kubectl diff compares already deployed resource, which we can get by:
kubectl get resource-type resource-name -o yaml
with the result of:
kubectl apply -f nginx.yaml --dry-run --output yaml
and not with actual content of your yaml file (simple cat nginx.yaml would be ok for that purpose).
You can additionally use:
kubectl get all -l "app.kubernetes.io/instance=<helm_release_name>" -o yaml
to get yamls of all resources belonging to specific helm release.
As you can read in man diff it has following options:
--from-file=FILE1
compare FILE1 to all operands; FILE1 can be a directory
--to-file=FILE2
compare all operands to FILE2; FILE2 can be a directory
so we are not limited to comparing single files but also files located in specific directory. Only we can't use these two options together.
So the full diff command for comparing all resources belonging to specific helm release currently deployed on our kubernetes cluster with yaml files from a specific directory may look like this:
diff -uN <(kubectl get all -l "app.kubernetes.io/instance=<helm_release_name>" -o yaml) --to-file=directory_containing_yamls/
Im not clear with the use of --record in kubectl command.
kubectl run nginx image=nginx --port=80 --record
detailed explanation with an example is much appreciated.
Using the --record flag when using kubectl annotates the objects created with that command with the command used to create them. When you list/retrieve these objects, the annotations will show up so that objects can be associated with a command.
I should warn you, however, that there is talk of deprecating this flag in the Kubernetes official repository here
https://github.com/kubernetes/kubernetes/pull/20035
and here
https://github.com/kubernetes/kubernetes/issues/40422
There must be "full-configuration" and example templates of Kubernetes YAML configs somewhere with comments itemizing what parameters do what with runnable examples somewhere.
Does anyone know where something like this might be? Or where the "full API" of the most commonly used Kubernetes components are?
There is documentation for every k8s api version available, for example check this link.
The way I found what every key in yaml file represent and what does it mean is via kubectl explain command.
For example:
$kubectl explain deploy.spec
Trick I use while doing CKAD to see full list could be:
$kubectl explain deploy --recursive > deployment_spec.txt
This will list all available options for kubernetes deployment that could you use in yaml file.
To generate some template there is option to use --dry-run and -o yaml in kubectl command, for example to create template for CronJob:
$kubectl run cron_job_name --image=busybox --restart=OnFailure --schedule="*/1 * * * * " --dry-run -o yaml > cron_job_name.yaml