I was really surprised to discover the other day that kubectl does not support running the same command against multiple Pods out of the box.
I get why that wouldn't be supported for interactive terminals, but seems like non-interactive commands should be fine.
Oh well. We can still do what we want thanks to UNIX tools like xargs.
kubectl get pods -o name | xargs -I{} kubectl exec {} -- <command goes here>
Just replace the <command goes here> bit with what you want to do.
Example: Setting Log Level to Debug for All Istio IngressGateway Envoys
Here's a real world example of when and how you might want to do this. The other day I was troubleshooting our Istio installation on a dev cluster and needed to set the log level of all of our ingress Envoy proxies to debug. One way to do this is to configure it through a POST request to each Envoy's admin /logging endpoint (on Istio this is on port 15000 by default).
We had five Envoys and I was feeling lazy, so I cooked up the following:
kubectl -n istio-system get pods -l app=istio-ingressgateway -o name | xargs -I{} kubectl -n istio-system exec {} -- curl -s localhost:15000/logging?level=debug -X POST
I'm sure there are other UNIX incantations that could do the same, but this got the job done for me and I'm proud of it. 😊👍
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