Finding the name of a new pod with kubectl

Question

I am new to k8s and I am running into a little problem here.

Here's the context: I need to invoke kubectl delete [podname] via a crontask once a day, and wait until k8s recreates the pod, then log into the container in that pod and run a shell command.

So I query the deployment and get something like this:

user@host:~$ kubectl get pods NAME                             READY     STATUS    RESTARTS   AGE firstpod-123456789-something           1/1       Running   570        2d secondpod-http-backend-something       1/1       Running   597        2d 

then I wrote a bash script that would delete the pods in a 5 minutes interval. That's the easy part.

Suppose I invoke kubectl delete firstpod-123456789-something and wait for k8s to recreate a new pod. That new pod would have a new name like firstpod-[some random hash here]-something

The problem is that I need to capture the name of that pod in my bash script so then I can exec a command in that pod like uname -a or whatever as to verify that the new pod is up and running just fine.

I googled it and read the kubectl docs but I don't think there's an easy way to do this via a bash script? I am assuming that the only way to get the pod name here would be via the k8s API?

I am happy to use any solution at this point. I wonder if there's any way that I rename the new pod when k8s spawns up a new one? so I could grep for a specific keyword?

Note that I don't want to egrep something like firstpod-[0-9]-something because that's just an example. A lot of pods have a lot of different names, that was just an example.

Thanks!

Answer 1

You need to label your deployment somehow, for example we set label app: myapp below:

apiVersion: extensions/v1beta1                                                                                                                                                                           kind: Deployment                                                                                                                                                                                         metadata:                                                                                                                                                                                                  name: nginx                                                                                                                                                                                      spec:                                                                                                                                                                                                      template:                                                                                                                                                                                                  metadata:                                                                                                                                                                                                  labels:                                                                                                                                                                                                    app: my-app                                                                                                                                                                                     spec:                                                                                                                                                                                                      containers:                                                                                                                                                                                              - image: nginx                                                                                                                                                             name: nginx   

After that you can get deployment's pod name very easy:

POD=$(kubectl get pod -l app=my-app -o jsonpath="{.items[0].metadata.name}") 

and execute some command there, for example:

kubectl exec -ti $POD -- uname -a 

Answer 2

Like Nickolay wrote, use a label to help selecting. Then you can use

kubectl get pods -l app=my-app -o custom-columns=:metadata.name 

This gets you the name of the pod that has the label "app=my-app"