TLDR: My understanding from learning all about K8s is that you need lots and lots of yaml files, however, I just deployed an app to a K8s clusters with 0 yaml files and it succeeded. Why is that? Does google cloud or K8s have defaults it uses when the app does not have any yaml file settings?
Longer:
I have a dockerized spring app that I deployed to a google cloud cluster I created via the UI.
It had 0 yaml files in there, so my expectation that kubectl deploy would fail, however, it succeeded and my stateless app is up there chugging away.
How does that work?
Well the gcp created for you in the background. I assume you pushed your docker image or CI to cluster and from there you just did few clicks right? same stuff you can do it on openshift environment. but in the background yaml file get's generated. if you edit the pod on your UI you will see that yaml file.
as above #Volodymyr Bilyachat said you can create deployment via imparative way or using declarative way(yaml). I would suggest always use declarative way.
you can see your deployment yaml file which you created from UI by doing
kubectl get deployment <deployment_name> -o yaml
kubectl get deployment <deployment_name> -o yaml > name.yaml #This will output your yaml file into name.yaml file
You can run your containers/pods using plain commands.
kubectl run podname --image=name
As you said 0 yaml files. But main idea of those files that you push them to source control and run test them via different environments using CI/CD.
Other benefit of yaml files that you can share configuration and someone else will be able to create infrastructure without having to write anything. Here is example how you can run elasticsearch with one command
kubectl apply -f https://download.elastic.co/downloads/eck/1.2.0/all-in-one.yaml
Related
I am setting up kubernetes for an application with 8 microservices,activemq,postgres,redis and mongodb.
After the entire configuration of pods and deployment ,is there any way to create a single master deployment yaml file which will create the entire set of services,replcas etc for the entire application.
Note:I will be using multiple deployment yaml files,statefulsets etc for all above mentioned services.
You can use this script:
NAMESPACE="your_namespace"
RESOURCES="configmap secret daemonset deployment service hpa"
for resource in ${RESOURCES};do
rsrcs=$(kubectl -n ${NAMESPACE} get -o json ${resource}|jq '.items[].metadata.name'|sed "s/\"//g")
for r in ${rsrcs};do
dir="${NAMESPACE}/${resource}"
mkdir -p "${dir}"
kubectl -n ${NAMESPACE} get -o yaml ${resource} ${r} > "${dir}/${r}.yaml"
done
done
Remember to specify what resources you want exported in the script.
More info here
Is there any way to create a single master deployment yaml file which will create the entire set of services,replicas etc for the entire application.
Since you already mentioned kubernetes-helm why don't you actually used it for that exact purpose? In short helm is sort of package manager for Kubernetes, some say similar to yum or apt. It deploys charts which you can actually refer to as packed application. Its pack of all your pre-configured applications which can be deploy as one unit. It's not entirely one file but more collection of files that build so called helm chart.
What are the helm charts?
Well they are basically K8s yaml manifest combined into a single package that can be installed to your cluster. And installing the package is just as simple as running single command such as helm install. Once done the charts are highly reusable which reduces the time for creating dev, test and prod environments.
As an example of a complex helm chart deploying multiple resources you many want to check Stackstorm.
Basically once deployed without any custom config this chart will deploy 2 replicas for each component of StackStorm as well as backends like RabbitMQ, MongoDB and Redis.
Okay first let me say please don't judge. Believe me, I am kicking myself in the ass.
So I lost my hard disk on my laptop which held the Kubernetes yaml files that I ran against a Kubernetes Cloud cluster. I don't have the latest backup which is the problem.
does anyone know how to get just the yaml I ran against the K8s cloud server. I can get to the cluster and run kubectl get pod my-pod -o yaml but of course, it adds a lot of things. I am just looking for the yaml that I ran.
I am stressing here and have learned my lesson. Backup, Backup and verify Backup.
You can use this and extend it to your needs:
kubectl get [resource type] -n [namespace] [resource Name] -o yaml > [output.yaml]
The -o yaml will do the job
Note
You will get some extra information provided by your cloud providers like history, version, and more.
Lens
https://k8slens.dev/
You can use Lens which will allow you to view & edit your resources so you will be able to copy the YAML from it.
Can anyone tell me the deployment flow for deploying the application over Kubernetes or EKS cluster using Jenkins. How is the deployment files updated based on the change of the docker image. If we have multiple deployment files and we change any image for any one of them. Do all of them are redeployed?
Can anyone tell me the deployment flow for deploying the application over Kubernetes or EKS cluster using Jenkins.
Make sure that your Jenkins instance has an IAM Role and updated kubeconfig so that it can access the Kubernetes cluster. If you consider running the pipeline on the Kubernetes cluster, Jenkins X or Tekton Pipelines may be good alternatives that are better designed for Kubernetes.
How is the deployment files updated based on the change of the docker image.
It is a good practice to also keep the deployment manifest in version control, e.g. Git. This can be in the same repository or in a separate repository. For updating the image after a new image is built, consider using yq. An example yq command to update the image in a deployment manifest (one line):
yq write --inplace deployment.yaml 'spec.template.spec.containers(name==<myapp>).image' \
<my-registy-host>/<my-image-repository>/<my-image-name>:<my-tag-name>
If we have multiple deployment files and we change any image for any one of them. Do all of them are redeployed?
Nope, Kubernetes Yaml is declarative so it "understand" what is changed and only "drives" the necessary deployments to its "desired state" - since the other deployments already are in its "desired state".
I applied a file xyz.yml sometime ago in EKS (Amazon elastic kubernetes service cluster) to deploy a statefulset pod from my local machine. This file is versioned in GitHub. However, there were few manual applies made using kubectl for this file to the kubernetes cluster after that, so it looks like the source file i have right now in GitHub might be out of sync from the cluster.
Is there a safe and easy way to retrieve this file in yaml directly from the cluster using kubectl so that i can use that from now in my GitHub source code. I do not want to make changes in my GitHub source code and then apply them to the cluster as the file might be out of sync.
If somehow i could directly retrieve the file in YAML from the kubernetes cluster, that would really help solve the problem. I tried --dry-run or kubectl diff but don't seem to be helping.
I am new to kubernetes, hence do not want to experiment with commands directly on the cluster.
Any help here would be greatly appreciated.
Cheers,
Ashley
You can try with edit:
kubectl -n <namespace name> edit [deployment, pod, svc] <name>
You can get the current YAML of individual resources with:
kubectl get <resource> -o yaml
But you can't get all the resources that you created with this file at once because Kubernetes doesn't keep track of the manifest files in which the resource definitions were supplied.
So you would need to check which resources were created by your file and get them individually as above. Or if all the resources in this file have common labels, perhaps you could get them more easily by these labels.
I created a .yaml file following this tutorial. You deploy the web service with kubectl apply -f shopfront-service.yaml. So far so good. The author says nothing though about how to tear everything down.
With TerraForm or CloudFormation you use the same .yaml file to remove all resources. I would think that K8 would also support cleaning up using the same .yaml file, but I can't find any way to do this.
Is there a way to delete resources with the same .yaml file used to create the deployment?
kubectl delete -f shopfront-service.yaml
see kubectl delete docs