Kubectl command to list pods of a deployment in Kubernetes

Question

Is there a way to use kubectl to list only the pods belonging to a deployment? Currently, I do this to get pods:

kubectl get pods| grep hello

But it seems an overkill to get ALL the pods when I am interested to know only the pods for a given deployment. I use the output of this command to see the status of all pods, and then possibly exec into one of them.

I also tried kc get -o wide deployments hellodeployment, but it does not print the Pod names.

Answer 1

There's a label in the pod for the selector in the deployment. That's how a deployment manages its pods. For example for the label or selector app=http-svc you can do something like that this and avoid using grep and listing all the pods (this becomes useful as your number of pods becomes very large):

$ kubectl get pods -l=app=http-svc 

or

$ kubectl get pods --selector=app=http-svc 

Answer 2

K8s components are linked to each other by labels and selectors. There are just no built-in attributes of My-List-of-ReplicaSets or My-List-Of-Pods for a deployment. You can't get them from kubectl describe or kubectl get

As @Rico suggested above, you have to use label filters. But you can't simply use the labels that you specify in the deployment metafile because deployment will generate a random hash and use it as an additional label.

For example, I have a deployment and a standalone pod that share the same label app=http-svc. While the first two are managed by the deployment, the 3rd one is not and shouldn't be in the result.

 ma.chi@~/k8s/deployments % kubectl get pods --show-labels NAME                   READY   STATUS    RESTARTS   AGE   LABELS http-9c89b5578-6cqbp   1/1     Running   0          7s    app=http-svc,pod-template-hash=574561134 http-9c89b5578-vwqbx   1/1     Running   0          7s    app=http-svc,pod-template-hash=574561134 nginx-standalone       1/1     Running   0          7s    app=http-svc ma.chi@~/k8s/deployments % 

The source file is

apiVersion: apps/v1 kind: Deployment metadata:   labels:     app: http-svc   name: http spec:   replicas: 2   selector:     matchLabels:       app: http-svc   strategy: {}   template:     metadata:       labels:         app: http-svc     spec:       containers:       - image: nginx:1.9.1         name: nginx1  ---  apiVersion: v1 kind: Pod metadata:   labels:     app: http-svc   name: nginx-standalone spec:   containers:   - image: nginx:1.9.1     name: nginx1-standalone 

To exact spot the containers created and managed by your deployment, you can use the script below(which is ugly, but this is the best I can do)

DEPLOY_NAME=http RS_NAME=`kubectl describe deployment $DEPLOY_NAME|grep "^NewReplicaSet"|awk '{print $2}'`; echo $RS_NAME  POD_HASH_LABEL=`kubectl get rs $RS_NAME -o jsonpath="{.metadata.labels.pod-template-hash}"` ; echo $POD_HASH_LABEL  POD_NAMES=`kubectl get pods -l pod-template-hash=$POD_HASH_LABEL --show-labels | tail -n +2 | awk '{print $1}'`; echo $POD_NAMES