Kubectl command to list pods of a deployment in Kubernetes
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)
here are some examples command line:
# single label
kubectl get pods -l=app=http-svc
kubectl get pods --selector=app=http-svc
# multiple labels
kubectl get pods --selector key1=value1,key2=value2
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