What is the purpose of kubectl logs deploy/my-deployment shown at https://kubernetes.io/docs/reference/kubectl/cheatsheet/#interacting-with-deployments-and-services?

I would think it will show me logs from all the pods deployed as part of the my-deployment object. However, even though I have 2 pods in my deployment, that command shows logs from only one of them.

CodePudding user response：

If your deployment has multiple pod replicas, then kubectl logs deployment/... will just pick one on its own.

Here is an example:

kubectl  get pods -n kube-system | grep coredns
coredns-78fcd69978-dqf95       1/1     Running   0          42h
coredns-78fcd69978-vgvf2       1/1     Running   0          42h

kubectl logs deployment/coredns -n kube-system 
Found 2 pods, using pod/coredns-78fcd69978-vgvf2

CodePudding user response：

As you can see from the documentation you linked:

kubectl logs deploy/my-deployment                         # dump Pod logs for a Deployment (single-container case)
kubectl logs deploy/my-deployment -c my-container         # dump Pod logs for a Deployment (multi-container case)

kubectl logs deploy/my-deployment is used when you have just one container. So in your case is probably taking the first one. If you have multiple containers you have to specify one with -c option.

If you want to have logs from multiple pods, you can use Stern

CodePudding user response：

By following documentation provided, when there are multiple Pods using the below command, it displays logs from only one Pod at a time it will pick randomly one at a point of time.

kubectl get pods -n kube-system | grep coredns

If there are multiple containers then one can specify by using “-c” and mention the container name. By following the Stren documentation, one can get the logs from multiple containers within a pod. Using the below command will display the multiple container data.

kubectl logs deploy/my-deployment -c my-container