I am studying "kubectl describe" sourcecodes at https://github.com/kubernetes/kubectl/blob/master/pkg/describe/describe.go
However, I still could not figure out how "kubectl decsribe [CRD]" works (as in which function/functions are called).
I am a Go newbie, so would like to get some pointers please. Thanks.
I have read describePod function and understand how it works more or less, but still could not figure out how "kubectl describe [CRD]" works.
The "kubectl describe " function can be found in the command-line interface (CLI) of Kubernetes, specifically in the "kubectl" tool. "kubectl" is used to manage and interact with a Kubernetes cluster and its resources.
enter image description here
Kubectl describe command helps to view the entire information about the kubernetes resources like Pods,deployments,services,nodes,jobs etc.
By using CRD(Custom Resource Definition) you can do CRUD operations like create, update, get and delete commands to access the resources. To use CRD we need to use the API groups.
Example:
Suppose you specify an API group as example.crd.com, which means you can issue the get, list, create, update, and delete commands to access the custom resources under the API group example.crd.com.
You can use kubectl describe crd <crd_name> to get a description of the CRD.
For more information refer this official doc
Try this similar SO’s SO1 and SO2 for more information
Related
Instead of navigating a namespace via e.g. :service, then :pod etc, I would like to see everything that's in the namespace in a single view. As if you would type kubectl -n argocd get all.
Can't find the info in the docs. Is this even possible?
Thanks for any suggestion!
Posting community wiki answer based on GitHub topic - Show multiple resource types without having to switch. Feel free to expand it.
That's true, there is no information about this in the documentation because simply there is no such possibility. There is open issue with this request on the GitHub page of k9s:
Is your feature request related to a problem? Please describe.
Oftentimes I'm watching/working on multiple resource types at the same time and it's very helpful to not have to switch from one to another. This is something very like kubectl get pod,deploy,... or kubectl get-all commands allows
Describe the solution you'd like
Being able to see multiple or all resources in the same screen without having to switch between resource types like:
:pod,configmap shows all pods & configmaps in the current namespace
or
:all shows all resources in the current namespace (get-all like)
Last pinged November 4 2021.
You can try
kubectl get all -n argocd -o yaml
or
kubectl get all -n argocd -o json
to list all common resources in a particular namespace
Note: It will not list the CRD or other custom resources like helm
I am working with kubernetes and kubectl commands, and am able to get a list of namespaces, and then can get the resources inside those namespaces. Question is, is there an effective way to monitor all resources (CRDs especially) in a certain namespace for changes? I know I could do this:
kubectl get myobjecttype -n <user-account-1>
and then check timestamps with a separate command, but that seems resource-taxing.
You might be looking for the Kubernetes Watch API.
In fact, you make a List request (see API reference for e.g. Pods) and add the watch=1 query parameter to get a continuous stream of changes to the specified resources.
kubectl also supports watches with the -w/--watch flag:
kubectl get myobjecttype -n <user-account-1> -w
How can we obtain the gke pod counts running in the cluster? I found there are ways to get node count but we needed pod count as well. it will be better if we can use something with no logging needed in gcp operations.
You can do it with Kubernetes Python Client library as shown in this question, posted by Pradeep Padmanaban C, where he was looking for more effective way of doing it, but his example is actually the best what you can do to perform such operation as there is no specific method which would allow you just to count pods without retrieving their entire json manifests:
from kubernetes import client , config
config.load_kube_config()
v1= client.CoreV1Api()
ret_pod = v1.list_pod_for_all_namespaces(watch=False)
print(len(ret_pod.items))
You can also use a different method, which allows to retrieve pods only from specific namespace e.g.:
list_namespaced_pod("default")
In kubectl way you can do it as follows (as proposed here by RammusXu):
kubectl get pods --all-namespaces --no-headers | wc -l
You can directly access the kubernetes API using a restful API call. You will need to make sure you provide the authentication token in your call by including a bearer token.
Once you are able to query the api server directly, you can use GET <master_endpoint>/api/v1/pods to list all the pods in the cluster. You can also search for specific namespaces by specifying the namespace /api/v1/namespaces/<namespace>/pods.
Keep in mind that the kubectl cli tool is just a wrapper for API calls, each kubectl command will form a RESTful API call in a similar format to the one listed above, so any interaction you have with the cluster using kubectl can also be achieved through RESTful API calls
I have installed a K8S cluster on laptop using Kubeadm and VirtualBox. It seems a bit odd that the cluster has to be up and running to see the documentation as shown below.
praveensripati#praveen-ubuntu:~$ kubectl explain pods
Unable to connect to the server: dial tcp 192.168.0.31:6443: connect: no route to host
Any workaround for this?
See "kubectl explain — #HeptioProTip"
Behind the scenes, kubectl just made an API request to my Kubernetes cluster, grabbed the current Swagger documentation of the API version running in the cluster, and output the documentation and object types.
Try kubectl help as an offline alternative, but that won't be as complete (limite to kubectl itself).
So the rather sobering news is that AFAIK there's not out-of-the box way how to do it, though you could totally write a kubectl plugin (it has become rather trivial now in 1.12). But for now, the best I can offer is the following:
# figure out which endpoint kubectl uses to retrieve docs:
$ kubectl -v9 explain pods
# from above I learn that in my case it's apparently
# https://192.168.64.11:8443/openapi/v2 so let's curl that:
$ curl -k https://192.168.64.11:8443/openapi/v2 > resources-docs.json
From here you can, for example, use jq to query for the descriptions. It's not as nice as a proper explain, but kinda is a good enough workaround until someone writes an docs offline query kubectl plugin.
The 'explain' documentation lives in the kube-apiserver and its resource definitions. Hence the need to connect to it through kubectl explain to get any docs. This is different from the standard very basic cli help from kubectl where it's in the kubectl Golang code.
So no workaround really other than setting up a dummy Kubernetes cluster and have kubectl point to it. Please note that CRDs help might not be available since they live in the deployed CRDs themselves.
I have a Kubernetes cluster running in minikube, I want to filter out all Logstash pods via Kubernetes API. Kubernetes API documentation is a bit confusing, I did some research and found out that I can use something like this, but I have been unsuccessful so far:
localhost:8000/api/v1/namespaces/default/pods?labelSelector=logstash
any ideas how to retrieve this? Any help would be really appreciated.
any ideas how to retrieve this?
Since labels are defined in <name>=<value> pairs you need to supply both, as described in the documentation (see the API section)
As an example, supposing you have:
namepace: default
labels on pods you want to select:
role=ops
application=logstash
kubectl proxy runs on localhost:8000
Then your api call would look like this:
curl localhost:8000/api/v1/namespaces/default/pods?labelSelector=role%3Dops,application%3Dlogstash